DMD1 - Module 14 - Blood Components And Hematopoiesis PDF

‭CHAPTER 14 UNSTOPPABLE BLEEDING‬ ‭BLOOD COMPONENTS AND HAEMATOPOIESIS‬ ‭ lood‬‭is‬‭a‬‭connective‬‭tissue‬‭made‬‭up‬‭of‬‭cellular‬‭elements‬‭suspended‬‭in‬‭an‬‭ECF‬‭matrix‬‭-‬‭plasma‬‭.‬‭Plasma‬‭makes‬‭up‬‭a‬‭¼‬‭of‬‭the‬ B ‭ECF, and acts as a buffer between the cells and the external environment....

‭CHAPTER 14 UNSTOPPABLE BLEEDING‬ ‭BLOOD COMPONENTS AND HAEMATOPOIESIS‬ ‭ lood‬‭is‬‭a‬‭connective‬‭tissue‬‭made‬‭up‬‭of‬‭cellular‬‭elements‬‭suspended‬‭in‬‭an‬‭ECF‬‭matrix‬‭-‬‭plasma‬‭.‬‭Plasma‬‭makes‬‭up‬‭a‬‭¼‬‭of‬‭the‬ B ‭ECF, and acts as a buffer between the cells and the external environment. The composition is; 2L cells, 3L plasma = 5L blood.‬ ‭Blood‬‭is‬‭a‬‭connective‬‭tissue‬‭made‬‭up‬‭of‬‭cellular‬‭elements‬‭suspended‬‭in‬‭an‬‭ECF‬‭matrix‬‭-‬‭plasma‬‭.‬‭Plasma‬‭makes‬‭up‬‭a‬‭¼‬‭of‬‭the‬ E‭ CF, and acts as a buffer between the cells and the external environment. The composition is; 2L cells, 3L plasma = 5L blood‬ ‭Role of blood‬ ‭‬ ‭Transport‬‭: gases, nutrients, waste, hormones, growth‬‭factors‬ ‭‬ ‭Regulation‬‭: temperature, pH, water‬ ‭‬ ‭Protection‬‭: prevent blood loss, infection control‬ ‭ omposition of blood‬ C ‭L>M>E>B.‬ ‭Lymphocytes‬‭mediate‬‭the‬‭acquired‬‭immune‬‭response‬‭of‬‭the‬‭body,‬‭20-35%‬‭of‬‭WBC.‬‭There‬‭are‬‭3‬‭subtypes;‬‭T‬‭cells,‬‭B‬‭cells,‬‭NK‬ ‭cells.‬ ‭Monocytes‬‭mature‬‭and‬‭enlarge‬‭in‬‭resident‬‭tissue;‬‭they‬‭are‬‭the‬‭precursor‬‭to‬‭macrophages.‬‭They‬‭can‬‭transit‬‭to‬‭tissues‬‭in‬‭8h,‬ ‭lifespan can be months/years. They engage in phagocytosis and secrete pro-inflammatory signal molecules (cytokines).‬ ‭Neutrophils‬‭are‬‭the‬‭most‬‭abundant‬‭WBC‬‭(50-70%),‬‭short‬‭life‬‭span‬‭(1-2‬‭days).‬‭They‬‭have‬‭2-5‬‭lobular‬‭segments‬‭of‬‭nucleus‬‭and‬ ‭engage in phagocytsosis by ingestion of bacteria and release a variety of cytokines and pyrogens (cause fever).‬ ‭Eosinophils‬ ‭are‬ ‭pink‬ ‭stained‬ ‭granules‬ ‭in‬ ‭cytoplasm,‬ ‭and‬ ‭are‬ ‭associated‬ ‭with‬ ‭allergic‬ ‭reactions‬‭and‬‭parasitic‬‭diseases.‬‭They‬ ‭have a cytotoxic cell type: release substances from granules that kill pathogens.‬ ‭Basophils‬‭are‬‭large,‬‭dark‬‭blue‬‭stained‬‭granules‬‭in‬‭cytoplasm‬‭and‬‭release‬‭inflammatory‬‭mediators-‬‭histamine,‬‭heparin,‬‭other‬ ‭cytokines.‬  ‭ latelets‬ ‭and‬ ‭platelet‬ ‭production;‬ ‭platelets‬ ‭are‬ ‭small,‬ ‭round‬ ‭and‬ ‭colourless‬ ‭with‬ ‭no‬ ‭nucleus.‬ ‭They‬ ‭contain‬ ‭mitochondria,‬ P ‭smooth‬‭ER‬‭and‬‭vesicles‬‭filled‬‭with‬‭cytokines,‬‭growth‬‭factors‬‭and‬‭clotting‬‭factors‬‭and‬‭are‬‭always‬‭present‬‭in‬‭the‬‭blood,‬‭life‬‭span‬ ‭of 7-10 days. They play a major role in haemostasis and thrombosis, but also have immune function.‬ T‭ he‬ ‭process‬ ‭of‬ ‭haematopoiesis‬ ‭is‬ ‭orchestrated‬ ‭by‬ ‭pluripotent‬ ‭hematopoietic‬ ‭stem‬ ‭cells‬‭,‬ ‭which‬ ‭possess‬ ‭the‬ ‭ability‬ ‭to‬ ‭differentiate‬ ‭into‬ ‭various‬ ‭subtypes‬ ‭of‬‭blood‬‭cells.‬‭This‬‭developmental‬‭journey‬‭commences‬‭early‬‭in‬‭embryonic‬‭development‬ ‭and‬ ‭persists‬ ‭throughout‬ ‭an‬ ‭individual's‬ ‭life.‬ ‭Hematopoiesis‬ ‭predominantly‬ ‭transpires‬ ‭within‬ ‭the‬ ‭bone‬ ‭marrow‬‭,‬ ‭initially‬ ‭in‬ ‭bones‬‭until‬‭the‬‭age‬‭of‬‭5,‬‭and‬‭subsequently‬‭in‬‭specific‬‭adult‬‭locations‬‭such‬ ‭as‬ ‭the‬ ‭pelvis,‬ ‭spine,‬ ‭ribs,‬ ‭cranium,‬ ‭and‬ ‭proximal‬ ‭ends‬ ‭of‬ ‭long‬ ‭bones.‬ ‭Approximately‬‭25%‬‭of‬‭the‬‭produced‬‭cells‬‭are‬‭red‬‭blood‬‭cells‬‭(‭R ‬ BCs‬‭),‬‭while‬ ‭the‬ ‭majority,‬ ‭constituting‬ ‭75%,‬ ‭are‬ ‭white‬ ‭blood‬ ‭cells‬ ‭(‭W ‬ BCs‬‭)‬ ‭with‬ ‭a‬ ‭shorter‬ ‭lifespan‬ ‭(due‬ ‭to‬ ‭the‬ ‭shorter‬ ‭lifespan,‬ ‭there‬ ‭needs‬ ‭to‬ ‭be‬ ‭more‬ ‭production).‬ ‭This‬ ‭process‬ ‭is‬ ‭primarily‬ ‭regulated‬ ‭by‬ ‭cytokines‬‭,‬ ‭including‬ ‭colony-stimulating‬ ‭factors,‬ ‭interleukins,‬ ‭and‬ ‭stem‬ ‭cell‬ ‭factor‬ ‭for‬ ‭white‬ ‭blood‬ ‭cells,‬ ‭erythropoietin‬ ‭for‬ ‭red‬ ‭blood‬ ‭cells,‬ ‭and‬ ‭thrombopoietin‬ ‭for‬ ‭platelets.‬ ‭Notably,‬ ‭immature‬ ‭blood‬ ‭cells‬ ‭undergo‬ ‭maturation‬ ‭within‬ ‭the‬ ‭bone‬ ‭marrow‬ ‭before‬ ‭entering‬ ‭the‬ ‭circulation.‬ ‭The‬ ‭head‬ ‭of‬ ‭long‬ ‭bones‬ ‭serves‬ ‭as‬ ‭a‬ ‭critical‬ ‭site‬ ‭for‬ ‭hematopoiesis‬ ‭due‬ ‭to‬ ‭its‬ ‭extensive‬ ‭blood‬ ‭supply‬‭,‬ ‭facilitating‬ ‭the‬ ‭immediate‬ ‭release‬ ‭of‬ ‭newly‬ ‭formed‬ ‭blood‬ ‭cells‬ ‭into‬ ‭the‬ ‭bloodstream‬ ‭upon‬ ‭production.‬ ‭This‬ ‭dynamic‬ ‭and‬ ‭finely‬ ‭tuned‬ ‭system‬‭ensures‬‭a‬‭continuous‬‭supply‬‭of‬‭functional‬‭blood‬‭cells‬‭essential‬‭for‬ ‭various physiological processes throughout an individual's life.‬ E‭ rythropoiesis‬‭,‬‭the‬‭process‬‭of‬‭red‬‭blood‬‭cell‬‭(RBC)‬‭production‬‭,‬‭is‬‭a‬‭highly‬ ‭regulated‬ ‭and‬ ‭essential‬ ‭physiological‬ ‭mechanism,‬‭generating‬‭approximately‬‭200‬ ‭billion‬ ‭cells‬ ‭per‬ ‭day.‬ ‭Control‬ ‭over‬ ‭erythropoiesis‬ ‭lies‬ ‭in‬ ‭the‬ ‭hands‬ ‭of‬ ‭the‬ ‭glycoprotein‬ ‭erythropoietin‬ ‭(EPO)‬ ‭and‬ ‭certain‬ ‭cytokines,‬ ‭with‬ ‭EPO‬ ‭being‬ ‭primarily‬‭produced‬‭by‬‭the‬‭kidneys‬‭.‬‭The‬‭release‬‭of‬‭EPO‬‭is‬‭triggered‬‭by‬‭hypoxia‬‭,‬‭a‬ ‭condition‬‭characterized‬‭by‬‭a‬‭lack‬‭of‬‭oxygen‬‭reaching‬‭the‬‭body's‬‭tissues,‬‭which‬‭can‬ ‭be‬‭induced‬‭by‬‭factors‬‭such‬‭as‬‭exercise‬‭or‬‭exposure‬‭to‬‭high‬‭altitudes‬‭.‬‭EPO‬‭is‬‭a‬‭key‬ ‭target‬‭in‬‭blood‬‭doping‬‭practices‬‭,‬‭as‬‭its‬‭administration‬‭stimulates‬‭the‬‭production‬ ‭of‬ ‭RBCs,‬ ‭leading‬ ‭to‬ ‭an‬ ‭increase‬ ‭in‬ ‭haematocrit‬ ‭and‬ ‭circulating‬ ‭haemoglobin‬ ‭levels‬ ‭in‬ ‭the‬ ‭blood.‬ ‭Within‬ ‭the‬ ‭bone‬ ‭marrow,‬ ‭committed‬ ‭progenitor‬ ‭cells‬ ‭transform‬ ‭into‬ ‭nucleated‬ ‭erythroblasts,‬ ‭initiating‬ ‭the‬ ‭process.‬ ‭As‬ ‭these‬ ‭cells‬ ‭progress,‬ ‭their‬ ‭nucleus‬ ‭shrinks‬ ‭from‬ ‭20‬ ‭micrometers‬ ‭to‬ ‭7‬ ‭micrometers.‬ ‭The‬ ‭pivotal‬ ‭step‬ ‭in‬ ‭erythropoiesis‬ ‭is‬ ‭enucleation‬‭,‬ ‭where‬‭the‬‭nucleus‬‭is‬‭pinched‬‭off‬‭and‬‭subsequently‬‭phagocytosed‬‭by‬‭bone‬‭marrow‬‭macrophages.‬‭This‬‭step,‬‭limiting‬‭the‬‭rate‬ ‭of‬ ‭RBC‬ ‭production,‬ ‭ensures‬ ‭the‬ ‭removal‬ ‭of‬ ‭the‬ ‭nucleus‬ ‭and‬ ‭other‬ ‭organelles,‬ ‭including‬ ‭mitochondria.‬ ‭The‬ ‭final‬ ‭immature‬ ‭stage‬‭in‬‭the‬‭bone‬‭marrow‬‭is‬‭the‬‭reticulocyte‬‭,‬‭which‬‭lacks‬‭a‬‭nucleus‬‭and‬‭swiftly‬‭leaves‬‭the‬‭bone‬‭marrow.‬‭Within‬‭24‬‭hours‬‭,‬‭the‬ ‭reticulocyte‬ ‭differentiates‬ ‭into‬ ‭a‬ ‭mature‬ ‭erythrocyte‬ ‭(RBC)‬ ‭in‬ ‭the‬ ‭bloodstream,‬ ‭fully‬ ‭equipped‬ ‭to‬ ‭perform‬ ‭its‬ ‭vital‬ ‭role‬ ‭in‬ ‭oxygen transport and gas exchange throughout the body.‬ ‭Stem cell → erythroblast (nucleated) → reticulocyte (enucleated) → mature RBC‬  ‭ latelets‬‭,‬ ‭essential‬ ‭components‬ ‭of‬ ‭the‬ ‭blood‬ ‭responsible‬ ‭for‬ ‭clot‬ ‭formation‬ ‭and‬ ‭wound‬ ‭healing,‬ ‭originate‬ ‭from‬ ‭a‬ ‭unique‬ P ‭process‬ ‭in‬ ‭the‬ ‭bone‬‭marrow.‬‭Megakaryocytes‬‭,‬‭large‬‭and‬‭distinct‬‭cells‬‭,‬‭undergo‬‭a‬‭specialized‬‭form‬‭of‬‭cell‬‭division‬‭known‬‭as‬ ‭endomitosis‬‭.‬‭During‬‭endomitosis,‬‭the‬‭megakaryocytes‬‭replicate‬‭their‬‭DNA‬‭up‬‭to‬‭seven‬‭times‬‭without‬‭undergoing‬‭cytokinesis‬‭,‬ ‭resulting‬ ‭in‬ ‭a‬ ‭polyploid‬ ‭state‬ ‭(N=128)‬‭.‬ ‭The‬ ‭growth‬ ‭and‬ ‭maturation‬ ‭of‬ ‭megakaryocytes‬ ‭are‬ ‭carefully‬ ‭regulated‬ ‭by‬ ‭thrombopoietin‬‭(‭T‬ PO‬‭),‬‭a‬‭glycoprotein‬‭that‬‭plays‬‭a‬‭crucial‬‭role‬‭in‬‭platelet‬‭production.‬‭As‬‭megakaryocytes‬‭undergo‬‭maturation‬ ‭and‬ ‭reach‬ ‭a‬‭sufficient‬‭size,‬‭platelets‬‭begin‬‭to‬‭form‬‭as‬‭cell‬‭fragments‬‭that‬‭bud‬‭off‬‭from‬‭the‬‭surface‬‭of‬‭the‬‭megakaryocytes‬‭.‬ ‭This‬‭process‬‭of‬‭platelet‬‭release‬‭involves‬‭the‬‭budding‬‭of‬‭small‬‭fragments‬‭into‬‭the‬‭blood‬‭vessels‬‭within‬‭the‬‭bone‬‭marrow.‬‭Once‬ ‭released‬‭into‬‭the‬‭bloodstream,‬‭these‬‭platelets‬‭circulate‬‭and‬‭play‬‭a‬‭pivotal‬‭role‬‭in‬‭responding‬‭to‬‭injuries,‬‭forming‬‭blood‬‭clots,‬ ‭and maintaining‬‭haemostasis‬‭.‬ ‭PHYSIOLOGY OF HAEMOSTASIS‬ ‭ aemostasis‬‭is the process to stop bleeding when injury‬‭occurs to a blood vessel. There are three major steps in the process;‬ H ‭steps 1 and 2 are primary haemostasis (prevented by antiplatelets), step 3 is secondary haemostasis (prevented by‬ ‭anticoagulants).‬ T‭ he‬‭first‬‭step‬‭involves‬‭vasoconstriction‬‭,‬‭a‬‭temporary‬‭reduction‬‭in‬‭blood‬‭flow‬‭within‬‭the‬‭damaged‬‭vessel.‬‭This‬‭constriction‬‭is‬ ‭induced‬‭by‬‭paracrine‬‭molecules‬‭released‬‭from‬‭the‬‭endothelium‬‭.‬‭Applying‬‭pressure‬‭achieves‬‭a‬‭similar‬‭effect,‬‭contributing‬‭to‬ ‭the overall mechanism of minimizing blood loss.‬ ‭The‬ ‭second‬ ‭step,‬ ‭formation‬ ‭of‬ ‭a‬ ‭platelet‬ ‭plug‬‭,‬ ‭commences‬ ‭with‬ ‭platelet‬ ‭adhesion‬ ‭to‬ ‭the‬ ‭damaged‬ ‭site,‬ ‭followed‬ ‭by‬ ‭activation‬‭and‬‭aggregation‬‭.‬‭Platelets‬‭in‬‭the‬‭blood‬‭bind‬‭to‬‭collagen‬‭in‬‭the‬‭injured‬‭endothelium‬‭through‬‭integrins‬‭.‬‭As‬‭platelets‬ ‭adhere,‬‭they‬‭release‬‭granules‬‭containing‬‭substances‬‭like‬‭ADP‬‭(providing‬‭energy)‬‭,‬‭calcium,‬‭serotonin,‬‭and‬‭platelet-activating‬ ‭factor‬ ‭(PAF)‬‭,‬‭initiating‬‭a‬‭positive‬‭feedback‬‭loop‬‭to‬‭attract‬‭and‬‭activate‬‭more‬‭platelets.‬‭This‬‭aggregation‬‭of‬‭platelets‬‭forms‬‭a‬ ‭plug‬ ‭that‬ ‭temporarily‬ ‭seals‬ ‭the‬ ‭breach‬ ‭by‬‭binding‬‭to‬‭fibrinogen/fibrin.‬‭Von‬‭Willebrand‬‭Factor‬‭(vWF)‬‭is‬‭an‬‭adhesive‬‭protein‬ ‭that‬ ‭helps‬ ‭platelets‬ ‭stick‬ ‭to‬ ‭damaged‬ ‭blood‬ ‭vessel‬ ‭walls‬ ‭when‬ ‭injured.‬ ‭Thus,‬ ‭the‬ ‭platelet‬ ‭is‬ ‭essential‬ ‭but‬ ‭temporary‬ ‭to‬ ‭strengthen the plug.‬ ‭The‬ ‭third‬ ‭step,‬ ‭coagulation‬‭,‬ ‭leads‬ ‭to‬ ‭the‬ ‭formation‬ ‭of‬ ‭a‬ ‭stable‬ ‭blood‬ ‭clot‬‭.‬ ‭Fibrinogen‬ ‭is‬ ‭converted‬ ‭to‬ ‭fibrin,‬ ‭an‬ ‭insoluble‬ ‭biopolymer‬‭that‬‭forms‬‭a‬‭network,‬‭trapping‬‭blood‬‭cells.‬‭Platelets,‬‭binding‬‭to‬‭fibrin‬‭or‬‭fibrinogen,‬‭contribute‬‭to‬‭platelet-platelet‬ ‭aggregation.‬ ‭Three‬ ‭pathways—the‬ ‭extrinsic,‬ ‭intrinsic,‬ ‭and‬ ‭convergence‬ ‭to‬ ‭the‬ ‭common‬ ‭pathway—lead‬ ‭to‬ ‭thrombin‬ ‭activation,‬ ‭ultimately‬ ‭resulting‬ ‭in‬ ‭fibrinogen‬ ‭conversion‬ ‭to‬ ‭fibrin.‬ ‭Positive‬‭feedback‬‭loops,‬‭where‬‭increased‬‭thrombin‬‭levels‬ ‭enhance‬ ‭intrinsic‬ ‭and‬ ‭extrinsic‬ ‭pathways,‬ ‭amplify‬ ‭the‬ ‭clotting‬‭response.‬‭Within‬‭the‬‭coagulation‬‭component,‬‭there‬‭is‬‭either‬ ‭extrinsic‬‭or‬‭intrinsic‬‭pathways,‬‭and‬‭both‬‭of‬‭these‬‭converge‬‭to‬‭the‬‭common‬‭pathway‬‭-‬‭need‬‭to‬‭memorise‬‭this.‬‭These‬‭pathways‬ ‭use calcium dependent enzymes.‬ ‭The intrinsic pathway is instigated by contact activation i.e. FXII gets activated by collagen, setting off a cascade.‬ ‭The extrinsic pathway is instigated by cell injury i.e. damage exposes tissue factor (FIII) leading to FVII activation.‬ ‭These‬ ‭two‬ ‭pathways‬‭converge‬‭which‬‭results‬‭in‬‭thrombin‬‭activation‬‭(FII),‬‭which‬‭then‬‭leads‬‭to‬‭fibrinogen‬‭conversion‬‭to‬‭fibrin‬ ‭(FI) (biopolymer), which then leads to cross linking of fibrin (via FXIII).‬ ‭Intrinsic begins within the blood vessel (slower), whereas extrinsic begins outside the blood vessel (faster).‬ ‭ oagulation factors can get disrupted - haemophilia type‬‭is dependent on the factor that is affected‬‭:‬ C ‭Haemophilia A:‬‭FVIII‬‭affected, 80-85% of cases → unstable‬‭clots, bleeding‬ ‭Haemophilia B: FIX‬‭affected, 10-15% of cases → bleeding‬ ‭ lot‬ ‭retraction‬ ‭and‬ ‭dissolution;‬ ‭after‬ ‭the‬ ‭platelet‬ ‭plug‬ ‭and‬ ‭coagulation‬ ‭forms‬ ‭a‬‭clot,‬‭the‬‭clot‬‭begins‬‭to‬‭shrink‬‭and‬‭fibrin‬‭is‬ C ‭broken‬ ‭down‬ ‭to‬ ‭fragments‬ ‭→‬ ‭fibrinolysis.‬ ‭Plasminogen‬ ‭is‬ ‭activated‬ ‭by‬ ‭tissue‬ ‭plasminogen‬ ‭activator‬ ‭(tPA),‬ ‭which‬ ‭forms‬ ‭plasmin‬ ‭-‬ ‭plasmin‬ ‭breaks‬ ‭down‬ ‭fibrin‬ ‭polymers‬ ‭into‬ ‭fibrin‬ ‭fragments‬ ‭(in‬ ‭fact,‬ ‭tPA‬ ‭is‬ ‭given‬ ‭to‬ ‭breakdown‬ ‭clots‬ ‭following‬ ‭strokes).‬ T‭ he‬‭role‬‭of‬‭endothelium;‬‭healthy‬‭endothelium‬‭maintains‬‭haemostasis‬‭in‬‭equilibrium‬‭and‬‭regulates‬‭many‬‭biomolecules‬‭that‬ ‭actively inhibit thrombosis. As such there are various structural components that play different roles;‬ ‭ ‬ S‭ tructural components‬ ‭‬ ‭tPA‬‭is produced by the endothelium and forms plasmin‬‭- fibrinolysis‬ ‭‬ ‭Heparan‬‭sulphate‬‭-‬‭forms‬‭glycocalyx‬‭that‬‭traps‬‭water‬‭and‬‭prevents‬‭molecules‬‭and‬‭platelets‬‭from‬‭interacting‬‭with‬‭the‬ ‭endothelium. Forms anti-thrombin factor that inhibits thrombosis‬ ‭‬ ‭Thrombomodulin‬‭- activates C-protein to inhibit thrombin‬‭and prevent coagulation‬ ‭‬ ‭Nitric oxide (NO) and prostacyclin (PGI2)‬‭- inactivate‬‭platelets‬ ‭‬ ‭CD39‬‭- inactivates platelets by restricting energy‬‭the blood can use (restricts ADP)‬ ‭THROMBOSIS‬ ‭ aemostasis vs thrombosis‬ H ‭Haemostasis‬‭is‬‭the‬‭process‬‭to‬‭stop‬‭bleeding‬‭when‬‭injury‬‭occurs‬‭to‬‭a‬‭blood‬‭vessel‬‭-‬ ‭equilibrium‬ ‭can‬ ‭be‬ ‭restored‬ ‭after‬ ‭haemostasis.‬ ‭It‬ ‭involves‬ ‭a‬ ‭balance‬ ‭between‬ ‭bleeding and thrombosis.‬ ‭Thrombosis‬ ‭is‬ ‭the‬ ‭pathological‬‭formation‬‭of‬‭blood‬‭clot‬‭-‬‭uncontrolled‬‭or‬‭excessive‬ ‭coagulation‬ ‭or‬ ‭platelet‬ ‭activation.‬ ‭This‬ ‭is‬ ‭due‬ ‭to‬ ‭inappropriate‬ ‭activation‬ ‭of‬ ‭the‬ ‭coagulation‬‭system‬‭or‬‭when‬‭regulatory‬‭mechanisms‬‭that‬‭prevent‬‭clot‬‭formation‬‭are‬ ‭disrupted.‬‭This‬‭can‬‭either‬‭be‬‭hereditary‬‭(e.g.‬‭haemophilia‬‭is‬‭sex‬‭linked)‬‭or‬‭acquired‬ ‭(anticoagulant/antiplatelet agents).‬ T‭ hrombosis‬‭- occurs via Virchow Triad (at least one‬‭of the following):‬ ‭Abnormal‬ ‭vessel‬ ‭wall:‬ ‭endothelial‬ ‭dysfunction/disturbances/damage,‬ ‭contact‬ ‭pathway‬ ‭activation‬ ‭(intrinsic),‬ ‭tissue‬ ‭factor‬ ‭release (extrinsic)‬ ‭Abnormal blood flow‬‭: venous obstructions/stasis, AF,‬‭aortic stenosis, mechanical valves‬ ‭Abnormal‬‭blood‬‭constituents‬‭:‬‭abnormalities‬‭in‬‭thrombin‬‭generation,‬‭platelets/coagulation‬‭and‬‭fibrinolytic‬‭pathways‬‭or‬‭other‬ ‭cellular components/microparticles‬ ‭A combination of these three creates an environment that promotes the formation of blood clots.‬ T‭ hrombosis occurs in various ways‬‭based on its location‬‭and aetiology;‬ ‭Arterial thrombosis:‬‭high shear force due to dysfunction‬‭in endothelial cell‬ ‭Venous thrombosis:‬‭low shear force due to valve involvement‬‭(within veins)‬ ‭Medical‬‭device‬‭thrombosis:‬‭high‬‭and‬‭low‬‭shear‬‭force‬‭due‬‭to‬‭blood‬‭clot‬‭+‬‭fibrin‬‭+‬‭platelet‬‭causes‬‭thrombosis‬‭on‬‭the‬‭medical‬ ‭implant surface‬ ‭ rterial‬ ‭thrombosis‬ ‭poses‬ ‭a‬ ‭significant‬ ‭risk,‬ ‭as‬‭it‬‭can‬‭lead‬‭to‬‭severe‬ A ‭consequences‬ ‭such‬ ‭as‬ ‭heart‬ ‭attacks‬ ‭or‬ ‭strokes‬‭.‬ ‭This‬ ‭type‬ ‭of‬ ‭thrombosis‬ ‭often‬ ‭stems‬ ‭from‬ ‭arterial‬ ‭narrowing‬ ‭caused‬ ‭by‬ ‭the‬ ‭buildup‬ ‭of‬ ‭lipids‬ ‭and‬ ‭cholesterol‬‭.‬ ‭The‬ ‭heightened‬ ‭blood‬ ‭flow,‬ ‭or‬ ‭shear‬ ‭stress‬‭,‬ ‭in‬ ‭the‬ ‭narrowed‬ ‭region‬ ‭triggers‬ ‭the‬ ‭activation‬ ‭of‬ ‭platelets‬‭and‬‭von Willebrand Factor (vWF)‬‭.‬ ‭vWF binds to collagen, unfolding and exposing receptors.‬ ‭Platelets‬ ‭roll‬ ‭along‬ ‭these‬ ‭receptors‬ ‭and‬ ‭are‬ ‭arrested‬ ‭through‬ ‭the‬ ‭integrin‬ ‭GPIb-V-IX,‬ ‭initiating‬ ‭adhesion‬ ‭through‬ ‭αIIbβ3‬ ‭and‬ ‭α2β1‬ ‭integrins.‬ ‭This cascade signals further platelets, leading to their aggregation.‬ ‭Fibrinogens‬ ‭circulating‬ ‭in‬ ‭the‬ ‭blood‬ ‭attach‬ ‭to‬ ‭platelets,‬ ‭promoting‬ ‭the‬ ‭formation‬ ‭and‬ ‭propagation‬ ‭of‬ ‭the‬ ‭thrombus.‬ ‭Downstream‬‭of‬‭the‬‭growing‬‭platelet‬‭clot,‬‭disturbed‬‭flow‬‭and‬‭coagulation‬‭contribute‬‭to‬‭the‬‭formation‬‭of‬‭a‬‭white‬‭clot,‬‭rich‬‭in‬ ‭platelets.‬‭Refer to image below for more information.‬  ‭ enous‬ ‭thrombosis‬‭,‬ ‭specifically‬ ‭deep‬ ‭vein‬ ‭thrombosis‬‭,‬ ‭occurs‬ V ‭due‬ ‭to‬ ‭blood‬ ‭flow‬ ‭stasis‬ ‭downstream‬ ‭of‬ ‭a‬ ‭vein‬ ‭valve‬‭.‬ ‭Reduced‬ ‭blood‬ ‭flow‬ ‭and‬ ‭stasis‬ ‭(low‬ ‭shear‬ ‭stress)‬ ‭impede‬ ‭the‬ ‭mass‬ ‭transport‬ ‭of‬ ‭coagulation‬ ‭factors‬ ‭downstream,‬ ‭leading‬ ‭to‬ ‭the‬ ‭accumulation‬‭of‬‭coagulation‬‭factors‬‭and‬‭activation‬‭of‬‭tissue‬‭factor‬ ‭(TF).‬ ‭This‬ ‭process‬ ‭results‬ ‭in‬ ‭the‬ ‭formation‬ ‭of‬ ‭a‬ ‭red‬ ‭clot,‬ ‭characterized by its richness in fibrin and red blood cells‬‭.‬ ‭ edical‬ ‭device‬ ‭thrombosis‬ ‭is‬ ‭triggered‬ ‭by‬ ‭contact‬ ‭with‬ M ‭foreign‬ ‭materials‬ ‭in‬ ‭medical‬ ‭devices,‬ ‭leading‬ ‭to‬ ‭protein‬ ‭adhesion‬ ‭and‬ ‭the‬ ‭activation‬ ‭of‬ ‭pathways‬ ‭that‬ ‭induce‬ ‭thrombosis.‬ ‭The‬ ‭flow‬ ‭conditions‬ ‭depend‬ ‭on‬‭the‬‭medical‬ ‭device‬ ‭geometry‬ ‭and‬ ‭blood‬ ‭flow,‬ ‭with‬ ‭examples‬‭ranging‬ ‭from‬‭low-flow‬‭shear‬‭situations‬‭(e.g.,‬‭venous‬‭catheter)‬‭to‬ ‭high-flow‬ ‭shear‬ ‭scenarios‬ ‭(e.g.,‬ ‭arterial‬ ‭mechanical‬ ‭valve).‬ ‭Certain‬ ‭medical‬ ‭devices,‬ ‭such‬ ‭as‬ ‭artificial‬ ‭hearts,‬ ‭may experience both high and low flow conditions.‬ E‭ mbolisms‬ ‭occur‬ ‭when‬ ‭blood‬ ‭clots‬ ‭break‬ ‭off‬ ‭and‬ ‭lodge‬ ‭downstream‬‭,‬ ‭causing‬ ‭further‬ ‭complications.‬ ‭Arterial‬ ‭embolisms‬‭,‬ ‭such‬‭as‬‭cerebral‬‭embolism,‬‭can‬‭result‬‭in‬‭strokes‬‭.‬‭Venous‬‭embolisms‬‭,‬‭including‬‭pulmonary‬‭embolism‬‭in‬‭the‬‭lungs‬‭or‬‭systemic‬ ‭embolism‬ ‭in‬ ‭areas‬ ‭like‬ ‭the‬ ‭legs,‬ ‭present‬ ‭additional‬ ‭challenges.‬ ‭Medical‬ ‭device‬ ‭embolisms‬ ‭depend‬ ‭on‬ ‭the‬ ‭location‬ ‭of‬‭the‬ ‭device in the body and can lead to diverse complications based on their specific contexts.‬ ‭ANTITHROMBOTICS‬ ‭ ntithrombotics:‬ ‭prevent‬ ‭formation‬ ‭of‬ ‭clots‬ ‭-‬ ‭these‬ ‭include‬ ‭antiplatelets‬ ‭and‬ ‭anticoagulants‬ ‭as‬ ‭these‬ ‭both‬ ‭contribute‬ ‭to‬ A ‭thrombosis.‬ ‭Antiplatelets:‬‭prevent platelet activitiy - coagulation‬‭activity could still theoretically occur‬ ‭Anticoagulants:‬‭prevent coagulant activity - platelet‬‭activity could still theoretically occur‬ ‭ latelet‬ ‭activation,‬ ‭adhesion,‬ ‭aggregation‬ ‭-‬ ‭Begins‬ ‭with‬ ‭damage‬ ‭to‬ ‭the‬ ‭endothelium‬ ‭which‬ ‭exposes‬ ‭collagen‬ ‭and‬ ‭vWF‬ P ‭(activation)‬‭,‬‭allowing‬‭binding‬‭of‬‭platelets‬‭to‬‭GP‬‭receptors‬‭(integrins)‬‭(adhesion)‬‭.‬‭Platelets‬‭then‬‭recruit‬‭other‬‭platelets‬‭by‬‭the‬ ‭release of other cofactors:‬ ‭‬ ‭COX-1 → produces thromboxane A2 (TxA2) → recruits more platelets‬ ‭○‬ ‭Aspirin inhibits COX1 → inhibits TxA2 → inhibits platelet recruitment‬ ‭‬ ‭ADP released from the cell acts on P2Y1/P2Y12 receptors on nearby platelets to recruit and adhese to them‬ ‭○‬ ‭Clopidogrel, prasugrel, ticagrelor inhibit the P2Y1/P2Y12 receptor‬ ‭Finally, platelets aggregate and form a haemostasis‬‭(aggregatrion).‬ S‭ imultaneously‬ ‭to‬ ‭platelet‬ ‭adhesion‬ ‭and‬ ‭aggregation,‬ ‭blood‬ ‭coagulation‬ ‭occurs,‬ ‭beginning‬ ‭with‬ ‭endothelial‬ ‭dysfunction‬‭,‬ ‭exposing‬ ‭tissue‬ ‭factor‬ ‭(activates‬ ‭FVII),‬ ‭and‬ ‭a‬ ‭cascade‬ ‭of‬ ‭interactions‬ ‭of‬ ‭factors.‬ ‭This‬ ‭activates‬ ‭thrombin‬ ‭(FIIa),‬ ‭converts‬ ‭fibrinogen to fibrin, fibrin causes cross linking to strengthen the clot.‬ ‭Warfarin‬‭inhibits‬‭FII, FVII, FIX, FX‬‭(old TV channels‬‭- it’s a Sydney thing :) ).‬ ‭Direct oral anticoagulants (DOAC) and heparin‬‭inhibits‬‭FXa, FIIa i.e. directly inhibits the common the pathway.‬ ‭ ntithrombotic drugs‬ A ‭Oral‬‭anticoagulants‬‭:‬‭d‭a‬ bigatran‬‭(‬‭d‭i‬rect‬‭thrombin‬‭inhibitor),‬‭apixaban/rivaroxaban‬‭(FXa‬‭inhibitors),‬‭Warfarin‬‭(Vit‬‭K‬‭antagonist‬‭-‬ ‭interferes with clotting factors in the liver).‬ ‭Injectable anticoagulants:‬‭heparin, low molecular‬‭weight heparin, fondaparinux (FXa inhibitor)‬ ‭Antiplatelets‬‭: aspirin, clopidogrel/ticagrelor/prasugrel‬‭(P2Y12 inhibitors), dipyridamole‬  I‭ nternational‬ ‭normalised‬ ‭ratio‬ ‭(INR)‬ ‭quantifies‬ ‭the‬ ‭length‬ ‭of‬ ‭time‬ ‭it‬ ‭takes‬ ‭for‬ ‭blood‬ ‭to‬ ‭clot.‬ ‭This‬ ‭is‬ ‭only‬ ‭for‬ ‭patients‬ ‭on‬ ‭warfarin.‬ ‭INR‬‭2-3‬‭is‬‭normal,‬‭but‬‭pts‬‭with‬‭prosthetic‬‭valves‬‭will‬‭need‬‭higher‬‭INR‬‭2.5-3.5‬‭-‬‭blood‬‭needs‬‭to‬‭take‬‭longer‬‭to‬‭clot‬‭because‬‭they‬ ‭have prosthetic valves → increased risk of clotting.‬ ‭ arfarin‬ ‭mechanism‬ ‭of‬ ‭action‬‭;‬ ‭R-warfarin‬ ‭inhibits‬ ‭vitamin‬‭K‬‭reductase‬‭from‬‭working,‬‭inhibiting‬‭the‬‭production‬‭of‬‭clotting‬ W ‭factors.‬ ‭Vitamin‬ ‭K‬ ‭reductase‬ ‭is‬ ‭a‬ ‭reduced‬ ‭version‬ ‭of‬ ‭Vitamin‬ ‭K,‬ ‭which‬ ‭operates‬ ‭to‬ ‭convert‬ ‭clotting‬ ‭factors‬ ‭from‬ ‭being‬ ‭non-functional‬ ‭to‬ ‭functional‬ ‭i.e.‬ ‭activates‬ ‭clotting‬ ‭factors‬ ‭from‬ ‭their‬ ‭inactivated‬ ‭form‬ ‭e.g.‬ ‭FVII‬ → ‭ ‬ ‭FVIIa‬ ‭(‘a’‬ ‭stands‬ ‭for‬ ‭activated). In their activated form, clotting factors are known as‬‭functional zymogens.‬‭Refer to diagram‬‭for more:‬ ‭ eparins‬ ‭and‬ ‭fondaparinux;‬ ‭antithrombin‬ ‭is‬ ‭synthesised‬ ‭in‬ ‭the‬ H ‭liver‬ ‭-‬ ‭it‬ ‭is‬ ‭an‬ ‭endogenous‬ ‭anticoagulant.‬ ‭It‬ ‭inhibits‬ ‭clotting‬ ‭factors 2a (thrombin) and 10a.‬ ‭Unfractionated‬ ‭heparin‬ ‭(snake‬ ‭looking)‬ ‭wraps‬ ‭around‬ ‭the‬ ‭anti-thrombin‬ ‭and‬ ‭thrombin‬ ‭molecules,‬ ‭and‬ ‭increases‬ ‭its‬ ‭effect‬ ‭as an anticoagulant (the chain has to be >18 molecules in length)‬ ‭Low‬ ‭molecular‬ ‭weight‬ ‭heparin‬ ‭-‬ ‭shorter‬ ‭than‬ ‭unfractionated‬ ‭heparin‬ ‭binds‬ ‭to‬ ‭10a‬ ‭moreso‬ ‭than‬ ‭2a‬ ‭(less‬ ‭so‬ ‭to‬‭thrombin,‬‭but‬ ‭moreso to antithrombin).‬ ‭Fondaparinux‬‭binds to antithrombin, only 10a, not‬‭2a‬ ‭Summary:‬ ‭Unfractionated - both 2a and 10a‬ ‭Low weight heparin - 10a predominantly, but also a little bit 2a‬ ‭Fondaparinux - only 10a‬ ‭Indications‬ ‭for‬ ‭anticoagulants‬ ‭or‬ ‭antiplatelets:‬ ‭atrial‬ ‭fibrillation,‬ ‭venous‬ ‭thromboembolism‬ ‭or‬ ‭pulmonary‬ ‭embolism,‬ ‭coronary artery disease, valvular heart disease, stroke‬ ‭Dental implications - need to balance the risk of bleeding with clotting‬ ‭‬ ‭Medical/medication history, including doses/indications‬ ‭‬ ‭Other medications such as NSAIDs and complementary/alternative medicine (can have an antithrombotic effect)‬ ‭‬ ‭Discuss with clinician managing patient‬ ‭‬ ‭Temporary interruption vs continuation of antithrombotic‬ ‭Patient‬ ‭related‬ ‭bleeding‬ ‭risk‬ ‭factors:‬ ‭increased‬ ‭blood‬ ‭pressure,‬ ‭decreased‬ ‭kidney/liver‬ ‭function‬ → ‭ ‬ ‭decreased‬ ‭ability‬ ‭to‬ ‭metabolise‬‭drugs‬‭→‬‭prolonged‬‭effect‬‭of‬‭medication‬‭→‬‭increased‬‭risk‬‭of‬‭bleeding,‬‭prior‬‭stroke,‬‭history‬‭of‬‭bleeding,‬‭bleeding‬  ‭ isorder,‬ ‭poor‬ ‭anticoagulant‬ ‭control‬ ‭-‬ ‭INR‬ ‭is‬ ‭fluctuating‬ ‭and‬ ‭poorly‬ ‭managed,‬ ‭increased‬ ‭age‬ ‭or‬ ‭frailty,‬ ‭NSAIDs,‬ ‭increased‬ d ‭alcohol consumption‬ ‭Procedure related‬‭bleeding risk factors‬ ‭Timing of cessation if indicated -‬‭only with consultation‬‭with prescriber‬ ‭‬ ‭Warfarin - 5 days prior to procedure‬ ‭‬ ‭DOAC - 24-72 hours (1-3 days) prior to procedure, depending on renal function and specific DOAC‬ ‭‬ ‭Antiplatelet - 5-7 days prior to procedure‬ L‭ ocal haemostatic measures‬ ‭Non-pharmacological‬‭:‬ ‭pressure‬ ‭to‬ ‭the‬ ‭wounds,‬ ‭decreased‬ ‭tissue‬ ‭trauma,‬ ‭cellulose‬ ‭and‬ ‭collagen‬ ‭(if‬ ‭indicated),‬ ‭sutures‬ ‭→‬ ‭closure of the wounds (if indicated)‬ ‭Pharmacological‬‭:‬ ‭transexamic‬ ‭acid‬ ‭mouthwash‬ ‭4.8%‬ ‭-‬ ‭antifibrinolytic‬ ‭agent‬ ‭-‬ ‭apply‬ ‭topically‬ ‭just‬ ‭before‬ ‭surgery,‬ ‭after‬ ‭the‬ ‭procedure,‬‭give‬‭the‬‭patient‬‭for‬‭home‬‭use‬‭x2‬‭days‬‭(10mL‬‭rinsed‬‭in‬‭mouth‬‭for‬‭2‬‭mins,‬‭then‬‭spit‬‭out,‬‭4‬‭times‬‭daily‬‭for‬‭2‬‭days).‬‭If‬ ‭the‬ ‭mouthwash‬ ‭can’t‬ ‭be‬ ‭compounded,‬ ‭crush‬ ‭500mg‬ ‭tablet‬ ‭of‬ ‭transexamic‬ ‭acid‬‭and‬‭disperse‬‭in‬‭10mL‬‭water.‬‭This‬‭works‬‭by‬ ‭inhibiting‬ ‭the‬ ‭breakdown‬ ‭of‬ ‭fibrin‬ ‭clots‬ ‭which‬ ‭are‬ ‭formed‬ ‭during‬ ‭the‬ ‭process‬ ‭of‬ ‭blood‬ ‭coagulation‬ ‭(blocks‬ ‭plasmin‬ ‭-‬ ‭the‬ ‭enzyme that breaks down fibrin).‬ ‭INTRODUCTION TO LEUKAEMIA AND LYMPHOMA‬ L‭ ymphoma‬ ‭and‬ ‭leukemia‬ ‭are‬ ‭both‬ ‭types‬ ‭of‬ ‭cancers‬‭that‬‭affect‬‭the‬‭blood‬‭and‬‭immune‬‭system,‬‭particularly‬‭lymphocytes,‬ ‭but they differ in their primary locations and manifestations.‬ L‭ ymphoma‬‭involves‬‭primary‬‭malignancy‬‭in‬‭lymph‬‭nodes.‬‭Lymphomas‬‭are‬‭cancers‬‭of‬‭lymphocytes,‬‭which‬‭are‬‭a‬‭type‬‭of‬‭white‬ ‭blood‬ ‭cell.‬ ‭The‬ ‭hallmark‬ ‭feature‬ ‭is‬ ‭the‬ ‭presence‬ ‭of‬‭abnormal‬‭lymphocytes‬‭in‬‭the‬‭lymphatic‬‭system,‬‭leading‬‭to‬‭lymph‬‭node‬ ‭enlargement‬ ‭and‬ ‭other‬ ‭symptoms.‬ ‭It‬ ‭is‬ ‭important‬ ‭to‬ ‭note‬ ‭that‬ ‭myeloid‬ ‭leukemias,‬ ‭which‬ ‭involve‬ ‭cells‬ ‭from‬ ‭the‬ ‭myeloid‬ ‭lineage, may also affect lymph nodes, but these cases are not classified as lymphomas.‬ L‭ eukemia‬ ‭involves‬ ‭primary‬ ‭malignancy‬ ‭in‬ ‭the‬ ‭blood‬ ‭and‬ ‭bone‬ ‭marrow.‬ ‭Leukemias‬ ‭affect‬ ‭white‬ ‭blood‬ ‭cells,‬ ‭and‬ ‭these‬ ‭abnormal‬ ‭cells‬‭circulate‬‭in‬‭the‬‭bloodstream.‬‭There‬‭are‬‭different‬‭types‬‭of‬‭leukemias,‬‭including‬‭chronic‬‭lymphocytic‬‭leukemia‬ ‭(CLL).‬ ‭In‬ ‭CLL,‬ ‭there‬ ‭is‬ ‭an‬ ‭increase‬ ‭in‬ ‭abnormal‬ ‭lymphocytes‬ ‭(white‬ ‭blood‬ ‭cells)‬ ‭in‬ ‭the‬‭blood‬‭and‬‭bone‬‭marrow,‬‭and‬‭lymph‬ ‭nodes may become enlarged. However, the primary manifestation is the presence of these cells in the blood.‬ I‭n‬‭summary,‬‭the‬‭key‬‭distinction‬‭lies‬‭in‬‭the‬‭primary‬‭location‬‭of‬‭the‬‭malignant‬‭cells.‬‭Lymphomas‬‭primarily‬‭involve‬‭lymph‬‭nodes,‬ ‭while leukemias involve the blood and bone marrow.‬ ‭ ellular‬ ‭origin‬ ‭of‬ ‭human‬ ‭B‬ ‭cell‬ ‭lymphomas‬ ‭and‬ C ‭leukaemias‬ ‭-‬ ‭begins‬ ‭with‬ ‭genetic‬ ‭deformation‬ ‭of‬ ‭the‬ ‭precursing‬ ‭B‬ ‭cell‬ ‭(don’t‬ ‭have‬ ‭to‬ ‭understand‬ ‭this‬ ‭chart,‬ ‭just‬ ‭know‬‭that‬‭lymphomas‬‭can‬‭be‬‭either‬‭B‬‭cell‬‭or‬‭T‬‭cell‬ ‭dominant (B cell is more common).‬ ‭‬ L‭ ymphoma‬‭:‬‭80%‬‭from‬‭B‬‭cells‬‭and‬‭20%‬‭are‬‭from‬ ‭T cells (T cell ones are worse)‬ ‭‬ ‭Leukaemia‬‭: 50% B cell and 50% T cell derived‬ ‭Starts‬ ‭off‬ ‭with‬ ‭B‬ ‭cell‬ ‭precursor‬ ‭in‬ ‭bone‬ ‭marrow‬ ‭(can‬ ‭develop‬‭all‬‭this‬‭disorders)‬‭→‬‭can‬‭also‬‭go‬‭to‬‭lymph‬‭node‬ ‭(germinal‬‭centre)‬‭to‬‭mature‬‭-‬‭can‬‭either‬‭become‬‭plasma‬ ‭or‬ ‭memory‬ ‭B‬ ‭cell‬ ‭-‬ ‭can‬ ‭develop‬ ‭into‬ ‭various‬ ‭diseases‬ ‭throughout.‬ ‭ aematopoiesis:‬ ‭begins‬ ‭as‬ ‭long‬ ‭term‬ ‭haematopoietic‬ ‭stem‬ ‭cell‬ ‭(LTHSC)‬ ‭→‬ ‭differentiates‬ ‭to‬ ‭short‬ ‭term‬ ‭HSC‬ ‭(STHSC)‬ ‭-‬ H ‭subtypes:‬ ‭‬ ‭Common lymhoid progenitor: T cells, B cells, NK cells‬ ‭‬ ‭Common‬ ‭myeloid‬ ‭progenitors:‬ ‭MEP‬ ‭(megakaryocyte,‬ ‭erythrocytes),‬ ‭GMP‬ ‭(granulocytes‬ ‭(WBCs),‬ ‭monocytes‬ ‭(macrophages))‬ ‭Types of lymphocytes‬‭- defined by surface antigens,‬‭function, and the type of illness when lacking:‬ ‭‬ ‭B cells - humoral immunity, responsible for antibody production‬ ‭‬ ‭T cells - cellular immunity, cytotoxicity against virus, fungi, provide help for B cells‬ → ‭ Most lymphomas are of B cell type.‬ ‭Primary‬‭lymphoid‬‭tissue‬‭-‬‭lymphocyte‬‭maturation‬‭-‬‭primary‬‭lymphoid‬‭tissue‬‭is‬‭the‬‭site‬‭at‬‭which‬‭B‬‭and‬‭T‬‭cells‬‭mature‬‭i.e.‬‭B‬ ‭cells in the bone marrow and T cells in the thymus.‬ ‭Secondary‬‭lymphoid‬‭tissue‬‭-‬‭lymphocytes‬‭brought‬‭into‬‭contact‬‭with‬‭antigen‬‭-‬‭secondary‬‭lymphoid‬‭tissue‬‭is‬‭the‬‭site‬‭at‬‭which‬ ‭B‬ ‭and‬ ‭T‬ ‭cells‬‭act‬‭on‬‭the‬‭antigen‬‭i.e.‬‭at‬‭lymph‬‭nodes‬‭-‬‭APC‬‭(dendritic‬‭cells)‬‭present‬‭the‬‭antigen‬‭to‬‭T‬‭cells,‬‭which‬‭then‬‭either‬ ‭help‬ ‭B‬ ‭cells‬ ‭(create‬ ‭Ig),‬ ‭or‬ ‭become‬ ‭cytotoxic‬ ‭in‬ ‭nature‬ ‭and‬ ‭kill‬‭the‬‭antigen‬‭e.g.‬‭adenoids,‬‭tonsils,‬‭spleen,‬‭appendix,‬‭Peyer’s‬ ‭patch‬ ‭Anatomy of lymph nodes‬ ‭‬ ‭Follicle centres contain predominantly B cells‬ ‭‬ ‭Cortical regions contain predominantly T cells‬  ‭Lymphoma‬ ‭Leukaemia‬ ‭ riginates‬ ‭in‬ ‭lymphatic‬ ‭system‬ ‭-‬ ‭includes‬ ‭lymph‬ ‭nodes,‬ o o ‭ riginates‬ ‭in‬ ‭bone‬ ‭marrow‬‭and‬‭affects‬‭production‬‭of‬‭blood‬ ‭spleen, thymus, and lymphoid tissue‬ ‭cells (RBC, WBC, platelets)‬ I‭nvolve‬‭uncontrolled‬‭growth‬‭and‬‭accumulation‬‭of‬‭cancerous‬ I‭nvolves‬ ‭overproduction‬‭of‬‭abnormal‬‭WBC‬‭(lymphocytes‬‭or‬ ‭lymphocytes (B, T, NK cells) in lymph node/tissue‬ ‭myeloid cells) in bone marrow‬ ‭Subtypes:‬‭Hodgkin lymphoma and non-Hodgkin lymphoma‬ S‭ ubtypes‬ ‭(based‬ ‭on‬ ‭the‬ ‭type‬ ‭of‬ ‭WBC‬ ‭affected):‬ ‭acute‬ ‭lymphoblastic‬ ‭leukaemia‬ ‭(ALL),‬ ‭acute‬ ‭myeloid‬ ‭leukemia‬ ‭(AML),‬ ‭chronic‬ ‭lymphocytic‬ ‭leukaemia‬ ‭(CLL),‬ ‭and‬ ‭chronic‬ ‭myeloid leukemia (CML)‬ → ‭ ‬ ‭Remember‬ ‭these‬ ‭are‬ ‭both‬ ‭types‬ ‭of‬ ‭cancers‬ ‭of‬ ‭the‬ ‭blood‬ ‭that‬ ‭affects‬ ‭the‬ ‭immune‬ ‭system‬ ‭-‬ ‭a‬ ‭lot‬ ‭of‬ ‭overlap,‬ ‭making‬ ‭diagnosis hard.‬ ‭WHO Classification System‬ ‭‬ ‭Non-Hodgins lymphoma - either B or T cell neoplasms‬ ‭‬ ‭Hodgkins lymphoma‬ ‭‬ ‭Plasma cell diseases‬ ‭‬ ‭Immunodeficiency-associated lymphoproliferative disorders‬ ‭B cell Non-Hodgkin Lymphoma‬ ‭‬ ‭Lymphoma/leukaemia‬ ‭‬ ‭Indolent nodal or extranodal lymphoma (slower)‬ ‭‬ ‭Aggressive nodal or extranodal lymphoma (faster)‬ ‭E.g. of extranodal is gastric/CNS‬ ‭Clinical features of lymphoma‬ ‭‬ ‭Lumps in neck, under arms, in groin (lymphadenopathy)‬ ‭‬ ‭Lymphadenopathy‬ ‭noted‬ ‭during‬ ‭examination‬ ‭for‬ ‭other‬‭reason‬‭(asymptomatic)‬‭during‬‭check‬ ‭up‬ ‭‬ ‭Abnormal‬ ‭blood‬ ‭findings‬ ‭unusual‬ ‭(compared‬ ‭with‬ ‭leukaemia‬ ‭-‬ ‭usually‬ ‭abnormal‬ ‭blood‬ ‭findings)‬ ‭‬ ‭Mycosis‬ ‭fungoides‬ ‭(type‬ ‭of‬ ‭cutaneous‬ ‭T‬ ‭cell‬ ‭lymphoma)‬ ‭-‬ ‭rash‬ ‭on‬ ‭skin;‬ ‭brown‬ ‭spots‬ ‭when‬ ‭cutaneous‬ ‭but‬ ‭once‬ ‭it‬ ‭becomes blood borne, known as sezary syndrome (cutaneous T cell lymphoma)‬ ‭‬ ‭Spleen involvement‬ ‭ iagnosis‬ ‭of‬ ‭lymphoma;‬ ‭requires‬ ‭a‬ ‭large‬ ‭tissue‬‭biopsy‬‭(histological‬‭assessment‬‭is‬‭the‬‭gold‬‭standard).‬‭If‬‭size‬‭of‬‭the‬‭tissue‬‭is‬ D ‭limited,‬ ‭then‬ ‭formalin‬ ‭fixing‬ ‭is‬ ‭the‬ ‭priority.‬ ‭Flow‬ ‭cytometry‬ ‭is‬ ‭a‬ ‭way‬ ‭of‬ ‭looking‬ ‭at‬ ‭surface‬ ‭protein‬ ‭expression‬ ‭of‬ ‭cells‬ ‭-‬ ‭cytogenetics (refer to diagram).‬ ‭‬ ‭Tissue biopsy → requires a large biopsy‬ ‭Histopathology of lymphoma‬ ‭‬ ‭H and E staining of different lymphomas, nucleus = purple colour‬ ‭‬ ‭Classified as either nodular (small nucleus) or diffuse (cannot differentiate b/c nuc or cells)‬ ‭‬ ‭If nodular/follicular (mostly small cells) → indolent‬ ‭‬ ‭If diffuse (mostly large cells) → aggressive‬ ‭80%‬ ‭of‬ ‭lymphoma‬ ‭can‬‭be‬‭divided‬‭into‬‭2‬‭groups;‬‭follicular‬‭make‬‭up‬‭40%‬‭of‬‭HL‬‭and‬‭the‬‭other‬‭40%‬‭is‬‭diffuse‬‭large‬‭B‬‭cell‬‭NHL‬ (‭ aggressive).‬ ‭Cancer‬‭is‬‭a‬‭clonal‬‭disorder‬‭-‬‭this‬‭means‬‭that‬‭if‬‭one‬‭cell‬‭mutates,‬‭it‬‭clones‬‭and‬‭becomes‬‭the‬‭predominant‬‭type‬‭of‬‭cell‬‭within‬ ‭the‬‭cellular‬‭population‬‭it‬‭is‬‭apart‬‭of,‬‭and‬‭causes‬‭monoclonality.‬‭Immunoglobulin‬‭(IG)‬‭expressed‬‭on‬‭the‬‭surface‬‭of‬‭B‬‭cells‬‭and‬ ‭IG‬ ‭made‬ ‭up‬ ‭of‬‭2‬‭heavy‬‭and‬‭2‬‭light‬‭chains‬‭-‬‭light‬‭chains‬‭can‬‭be‬‭kappa‬‭or‬‭lambda‬‭(K‬‭and‬‭L‬‭on‬‭pic)‬‭2/3‬‭are‬‭kappa‬‭and‬‭1/3‬‭are‬ ‭lambda‬‭(ratio‬‭2:1).‬‭In‬‭malignancy,‬‭one‬‭is‬‭more‬‭than‬‭the‬‭other‬‭(more‬‭often‬‭the‬‭L‬‭cells),‬‭and‬‭this‬‭presents‬‭on‬‭the‬‭graph‬‭(right‬ ‭graph‬‭is‬‭malignant).‬‭This‬‭is‬‭due‬‭to‬‭lack‬‭of‬‭apoptosis,‬‭causing‬‭increased‬‭clonality‬‭of‬‭the‬‭cell‬‭type.‬‭CD20‬‭is‬‭a‬‭marker‬‭for‬‭B‬‭cells;‬ ‭using‬‭cytometry‬‭, we can see the ratio of L:K cells.‬ ‭Gene translocation in lymphoma‬‭; different types of‬‭genes that are altered can lead to different lymphomas.‬ L‭ ymphoma staging‬ ‭Stage 1 - early disease‬‭- cancer is found only in‬‭a single lymph node region or one organ or area outside the lymph node‬ ‭Stage 2 - locally advanced disease‬‭- the cancer is‬‭found in two or more lymph node regions on one side of the diaphragm‬ ‭Stage 3 - advanced disease‬‭- the disease involves‬‭lymph nodes both above and below the diaphragm‬ ‭Stage‬ ‭4‬ ‭-‬ ‭widespread‬ ‭disease‬ ‭-‬ ‭lymphoma‬ ‭has‬ ‭advanced‬ ‭beyond‬ ‭the‬ ‭lymph‬ ‭nodes‬ ‭and‬‭spleen‬‭AND‬‭has‬ ‭spread to one or more organ - bone, bone marrow, skin, liver‬ ‭Diagnosis of staging based on glucose labelling that emits a small amount of radiation → PET SCAN:‬ ‭‬ ‭Brain lights up normally‬ ‭‬ ‭Black spots are lymphoma though‬ ‭‬ ‭Figure is stage 4 lymphoma - diffuse large B cell lymphoma‬ ‭Treatment strategies‬ ‭Grow slowly → treat slowly (indolent):‬ ‭‬ ‭Watch and wait‬ ‭‬ ‭Local radiation for local disease‬ ‭‬ ‭Start with simple chemotherapy and move to more complex chemotherapy‬ ‭Grow fast → treat fast (aggressive)‬ ‭‬ ‭Aggressive multiagent chemotherapy, often with radiation therapy to sites of bulky disease‬ ‭‬ ‭Consider autologous or allogeneic stem cell transplantation‬ ‭‬ ‭Redo PET scan to see if it has gone down‬ ‭‬ ‭Repeat in 5 years‬ ‭Common anti-lymphoma drugs‬ ‭‬ ‭Chlorambucil‬ ‭‬ ‭CHOP: cyclophosphamide, doxorubicin, vincristine, prednisone‬ ‭‬ ‭Fludarabine‬ ‭‬ ‭Bendamustine‬ ‭‬ ‭Monoclonal antibodies‬ ‭○‬ ‭Anti CD20 (expressed by B lymphocytes)‬ ‭○‬ ‭Anti CD52 (B and T lymphocytes, monocytes dendritic cells)‬ ‭Outcomes of therapy‬ ‭‬ ‭Indolent: No cure, median survival 8 years, 25% alive in 10 years‬ ‭‬ ‭Aggressive: cure 30-40%, 50% dead in 2 years‬ → ‭ indolent eventually dead, but no cure. Aggressive can be cured in 30-40%, but 50% dead in 2 years.‬ ‭Acute Leukaemia‬ ‭Chronic Leukaemia‬ T‭ imeline:‬ ‭rapidly‬ ‭progressive‬ ‭if‬ ‭untreated‬ ‭→‬ ‭severe‬ ‭bone‬ T‭ imeline:‬ ‭slower‬ ‭course,‬ ‭even‬ ‭non-progressive,‬ ‭marrow‬ ‭marrow‬‭failure‬‭and‬‭no‬‭opportunity‬‭for‬‭body‬‭to‬‭compensate‬ ‭failure‬ ‭often‬ ‭not‬ ‭present‬ ‭at‬ ‭diagnosis‬ ‭and‬ ‭physiological‬ ‭ progression days/weeks → survival weeks/months‬ → ‭compensation‬ ‭possible‬ ‭for‬ ‭some‬ ‭symptoms‬‭→‬‭progression‬ ‭weeks/months → survival months/years‬ ‭Presenting features:‬‭bone marrow failure, bone pain‬ ‭ resenting‬ ‭features:‬ ‭non-specific‬ ‭complains‬ ‭(often‬ ‭picked‬ P ‭up‬ ‭on‬ ‭routine‬ ‭blood‬ ‭tests,‬ ‭symptoms‬ ‭related‬ ‭to‬ ‭splenomegaly or lymphadenopathy‬ ‭ athobiology:‬ ‭deregulation‬ ‭of‬ ‭differentiation‬ ‭and‬ P ‭ athobiology:‬‭results‬‭from‬‭the‬‭neoplastic‬‭transformation‬‭of‬ P ‭maturation‬ ‭programs‬ ‭→‬ ‭characterised‬ ‭by‬ ‭abundance‬ ‭of‬ ‭a‬ ‭haematopoietic‬ ‭stem‬ ‭cell,‬ ‭some‬ ‭blast‬ ‭cells‬ ‭present,‬ ‭but‬ ‭immature‬ ‭‘blastic’‬ ‭cells‬ ‭that‬ ‭grow‬ ‭uncontrollably‬ ‭and‬ ‭lack‬ ‭more mature cells that can carry out their normal functions‬ ‭normal differentiation‬ ‭Summary:‬‭mature cells > blast cells‬ ‭Summary:‬‭blast cells > mature cells‬ ‭ athobiology:‬‭clonal‬‭disorder‬‭that‬‭results‬‭from‬‭haematopoietic‬‭progenitors‬‭(either‬‭lymphoid‬‭or‬‭myeloid‬‭pathways,‬‭or‬‭from‬ P ‭primitive stem cells, decreased apoptosis.‬ L‭ ack‬ ‭of‬ ‭normal‬ ‭haematopoiesis‬ ‭can‬ ‭cause‬ ‭bone‬ ‭marrow‬ ‭failure:‬ ‭Anaemia‬‭→ fatigue, shortness of breath‬ ‭Neutropaenia‬‭→ infection and mouth ulcers‬ ‭Thrombocytopaenia‬‭→ bleeding and bruising‬ E‭ xcess malignant blood cells:‬ ‭High WBC in blood → hyperviscosity →‬‭stroke‬ ‭Increase‬ ‭in‬ ‭size‬ ‭of‬ ‭secondary‬ ‭lymphoid‬ ‭tissue‬ ‭→‬ ‭splenomegaly‬‭and‬‭lymphadenopathy‬ ‭Bone pain‬ ‭ cute Myeloblastic Leukaemia (AML)‬‭is:‬ A ‭Acute → high blasts, low mature cells‬ ‭Myelo → myeloid cells (RBC, platelets, monocytes, granulocytes)‬ ‭Leukaemia → WBC‬ ‭E.g.‬‭64‬‭year‬‭old‬‭man‬‭with‬‭5‬‭day‬‭history‬‭of‬‭fever,‬‭shortness‬‭of‬‭breath‬‭and‬‭bruising‬‭of‬‭the‬‭leg.‬‭The‬‭blood‬‭test‬‭below‬‭shows‬‭that‬ ‭he is anaemia (Hb = 84), neutropaenic (0.1), low myeloblasts and low platelets.‬ ‭Anaemic + neutropaenic + thrombocytopaenic → pancytopaenia; low in all 3.‬ ‭ cute Lymphoblastic Leukaemia (ALL)‬‭is:‬ A high blast cells, neutrophil normal range ‭Acute → high blasts, low mature cells‬ Low platelets ‭Lympho → lymphoid cells (T and B cells)‬ ‭Leukaemia → WBC‬ ‭Other‬ ‭features:‬ ‭cervical‬ ‭and‬ ‭supraclavicular‬ ‭lymphadenopathy,‬ ‭large mediastinal mass, heavy infiltration of CD2+ blast cells‬ ‭E.g.‬ ‭39yo‬ ‭male‬ ‭presents‬ ‭with‬ ‭swelling‬ ‭in‬ ‭neck‬ ‭for‬ ‭1‬ ‭week,‬ ‭terminal‬‭deoxy‬‭nucleoid‬‭transferase‬‭positivity‬‭(TDT+)‬‭tells‬‭us‬‭that‬ ‭it is T-cell ALL. Lymphocytes would be high in a blood test.‬ ‭ hronic‬ ‭lymphocytic‬ ‭leukaemia‬ ‭is‬ ‭a‬ ‭disease‬ ‭of‬ ‭the‬ ‭elderly‬ ‭-‬ C ‭median‬ ‭age‬ ‭of‬ ‭onset‬ ‭is‬ ‭65.‬ ‭It‬ ‭involves‬ ‭the‬ ‭accumulation‬ ‭of‬ ‭functionally‬ ‭incompetent‬ ‭mature‬ ‭lymphocytes‬ ‭in‬ ‭blood,‬ ‭bone‬‭marrow,‬‭spleen,‬‭lymph‬‭nodes.‬‭Lymphocytes‬‭are‬‭monoclonal;‬ ‭almost always a B cell disorder (B-CLL) with associated complications.‬ ‭ linical‬ ‭presentation‬ ‭is‬ ‭predominantly‬ ‭asymptomatic,‬ ‭but‬ ‭raised‬ ‭lymphocyte‬ ‭count‬ ‭on‬‭blood‬‭count‬‭and‬‭lymphadenopathy.‬ C ‭Others‬ ‭include‬ ‭immune‬ ‭dysfunction‬ ‭(viral‬ ‭infections‬ ‭e.g.‬ ‭shingles),‬ ‭and‬ ‭other‬ ‭symptoms‬ ‭of‬ ‭marrow‬ ‭failure;‬ ‭anaemia‬ ‭-‬ ‭tiredness, SOB, low platelet count - easy bruising, bleeding, low neutrophil count ( → bacterial infection).‬ ‭ linical‬ ‭course‬ ‭follows‬ ‭a‬ ‭slow‬ ‭progression,‬ ‭marked‬‭by‬‭a‬‭gradual‬‭increase‬‭in‬‭the‬‭white‬‭blood‬‭cell‬‭count‬‭primarily‬‭due‬‭to‬‭the‬ C ‭accumulation‬ ‭of‬ ‭abnormal‬ ‭lymphocytes.‬ ‭As‬ ‭the‬ ‭disease‬ ‭advances,‬ ‭there‬ ‭is‬ ‭notable‬‭enlargement‬‭of‬‭lymph‬‭nodes,‬‭liver,‬‭and‬ ‭spleen.‬‭Progressive‬‭bone‬‭marrow‬‭failure‬‭becomes‬‭evident,‬‭leading‬‭to‬‭compromised‬‭hematopoiesis‬‭including‬‭immune‬‭paresis‬ ‭and‬ ‭B‬ ‭cell‬ ‭immunosuppression,‬‭contributing‬‭to‬‭an‬‭increased‬‭susceptibility‬‭to‬‭infections.‬‭Additionally,‬‭patients‬‭with‬‭CLL‬‭may‬ ‭exhibit‬‭the‬‭secretion‬‭of‬‭a‬‭paraprotein,‬‭an‬‭abnormal‬‭protein‬‭produced‬‭by‬‭the‬‭cancerous‬‭lymphocytes.‬ ‭This‬ ‭can‬ ‭lead‬ ‭to‬ ‭a‬ ‭complication‬ ‭known‬ ‭as‬ ‭autoimmune‬ ‭haemolytic‬ ‭anemia,‬ ‭where‬ ‭the‬ ‭immune‬ ‭system‬ ‭attacks‬ ‭and‬ ‭destroys‬ ‭red‬ ‭blood‬ ‭cells,‬ ‭leading‬ ‭to‬ ‭anemia.‬ ‭Another‬ ‭complication‬ ‭is‬ ‭immune‬ ‭thrombocytopenia‬ ‭purpura,‬ ‭a‬ ‭condition‬ ‭characterized‬ ‭by‬ ‭low‬ ‭platelet‬ ‭counts,‬ ‭which‬ ‭can‬ ‭result‬ ‭in‬ ‭excessive bruising and bleeding.‬ T‭ he‬ ‭aetiology‬ ‭of‬ ‭chronic‬ ‭lymphocytic‬ ‭leukaemia‬ ‭(CLL)‬ ‭remains‬ ‭largely‬ ‭unknown,‬ ‭with‬ ‭multiple‬ ‭factors‬ ‭contributing‬ ‭to‬ ‭its‬ ‭development.‬ ‭Immune‬ ‭regulation‬ ‭plays‬ ‭a‬ ‭role‬ ‭in‬ ‭CLL,‬ ‭and‬ ‭approximately‬ ‭80%‬ ‭of‬ ‭cases‬ ‭involve‬ ‭somatic‬ ‭gene‬ ‭mutations.‬ ‭Notably,‬ ‭mutations‬ ‭in‬ ‭tumour‬ ‭suppressor‬ ‭genes,‬ ‭such‬ ‭as‬ ‭ATM‬ ‭and‬ ‭p53,‬ ‭are‬ ‭prevalent‬ ‭in‬ ‭CLL.‬ ‭One‬ ‭significant‬ ‭molecular‬ ‭alteration‬ ‭observed‬ ‭in‬ ‭CLL‬ ‭is‬ ‭the‬ ‭elevation‬ ‭of‬ ‭the‬ ‭anti-apoptotic‬ ‭protein‬ ‭bcl-2,‬ ‭attributed‬ ‭to‬ ‭the‬ ‭deletion‬ ‭of‬ ‭inhibitory‬  ‭ icroRNA.‬ ‭This‬ ‭dysregulation‬ ‭of‬ ‭apoptosis,‬ ‭or‬ ‭programmed‬ ‭cell‬ ‭death,‬ ‭contributes‬ ‭to‬ ‭the‬ ‭survival‬ ‭and‬ ‭accumulation‬ ‭of‬ m ‭abnormal‬ ‭lymphocytes‬ ‭characterizing‬ ‭CLL.‬ ‭There‬ ‭is‬ ‭also‬ ‭an‬ ‭element‬ ‭of‬ ‭inherited‬ ‭risk‬ ‭associated‬ ‭with‬ ‭CLL.‬ ‭Individuals‬ ‭with‬ ‭first-degree‬‭relatives‬‭affected‬‭by‬‭CLL‬‭have‬‭an‬‭increased‬‭risk,‬‭although‬‭there‬‭is‬‭no‬‭consensus‬‭on‬‭a‬‭singular‬‭gene‬‭responsible‬‭for‬ ‭the‬‭development‬‭of‬‭the‬‭disease.‬‭The‬‭interplay‬‭of‬‭genetic‬‭factors‬‭and‬‭environmental‬‭influences‬‭underscores‬‭the‬‭complexity‬‭of‬ ‭CLL's aetiology,‬ T‭ he‬ ‭diagnosis‬ ‭of‬ ‭chronic‬ ‭lymphocytic‬ ‭leukaemia‬ ‭(CLL)‬ ‭involves‬ ‭specific‬ ‭criteria‬ ‭and‬ ‭diagnostic‬ ‭procedures‬ ‭to‬ ‭identify‬ ‭the‬ ‭characteristic‬‭features‬‭of‬‭this‬‭blood‬‭and‬‭bone‬‭marrow‬‭disorder.‬‭One‬‭essential‬‭criterion‬‭for‬‭CLL‬‭diagnosis‬‭is‬‭the‬‭presence‬‭of‬‭a‬ ‭peripheral‬ ‭blood‬ ‭monoclonal‬ ‭B-cell‬ ‭population,‬ ‭exceeding‬ ‭a‬ ‭count‬ ‭of‬ ‭>5x10^9/L,‬ ‭persisting‬ ‭for‬ ‭at‬ ‭least‬ ‭four‬‭weeks.‬‭The‬ ‭characteristic‬ ‭B-cell‬‭population‬‭in‬‭CLL‬‭co-expresses‬‭CD19,‬‭CD5,‬‭and‬‭CD23.‬‭Additionally,‬‭there‬‭is‬‭typically‬‭weak‬‭expression‬‭of‬ ‭CD20,‬‭CD79B,‬‭and‬‭surface‬‭IgM‬‭on‬‭these‬‭B‬‭cells.‬‭While‬‭a‬‭bone‬‭marrow‬‭biopsy‬‭is‬‭not‬‭mandatory‬‭for‬‭diagnosing‬‭CLL,‬‭it‬‭can‬‭be‬ ‭beneficial‬ ‭in‬ ‭certain‬ ‭cases.‬ ‭Bone‬ ‭marrow‬‭biopsy‬‭is‬‭particularly‬‭useful‬‭when‬‭there‬‭is‬‭a‬‭need‬‭to‬‭determine‬‭if‬‭cytopenias‬‭(low‬ ‭blood‬ ‭cell‬ ‭counts)‬ ‭are‬‭a‬‭result‬‭of‬‭bone‬‭marrow‬‭infiltration‬‭by‬‭CLL‬‭cells.‬‭This‬‭procedure‬‭provides‬‭valuable‬‭information‬‭about‬ ‭the‬ ‭extent‬ ‭of‬ ‭CLL‬ ‭involvement‬ ‭in‬ ‭the‬ ‭bone‬ ‭marrow‬ ‭and‬ ‭aids‬‭in‬‭assessing‬‭the‬‭impact‬‭on‬‭haematopoiesis.‬‭Other‬‭diagnostics‬ ‭include‬ ‭WBC‬‭count‬‭is‬‭very‬‭elevated‬‭(lymphocyte‬‭count‬‭-‬‭although‬‭normal‬‭neutrophil‬‭count),‬‭platelet‬‭count‬‭is‬‭retained,‬‭flow‬ ‭cytometry shows more kappa and less lambda chains (express CD20+CD5+CD23 B lymphocytes).‬ S‭ taging‬ ‭systems‬ ‭in‬ ‭CLL‬ ‭are‬ ‭used‬ ‭to‬ ‭classify‬ ‭the‬ ‭severity‬ ‭and‬ ‭progression‬ ‭of‬ ‭CLL.‬ ‭Rai‬ ‭staging‬ ‭is‬ ‭based‬ ‭on‬ ‭the‬ ‭presence‬ ‭or‬ ‭absence‬ ‭of‬ ‭certain‬ ‭clinical‬ ‭findings‬ ‭and‬ ‭blood‬ ‭counts,‬ ‭whereas‬ ‭Binet‬ ‭staging‬ ‭is‬ ‭based‬ ‭on‬ ‭the‬ ‭extent‬ ‭of‬ ‭lymphadenopathy‬ ‭(enlarged lymph nodes) and presence of anaemia/thrombocytopaenia. Treatment begins at RAI stage 2-3 or Binet stage C.‬ ‭ rognosis‬‭follows‬‭one‬‭of‬‭two‬‭paths,‬‭depending‬‭on‬‭the‬‭mutated‬‭status‬‭-‬‭this‬‭can‬‭be‬‭determined‬‭by‬‭observing‬‭the‬‭expression‬‭of‬ P ‭immunoglobulin‬ ‭(Ig)‬ ‭variable‬ ‭(V)‬ ‭heavy‬ ‭chain‬ ‭(H)‬ ‭gene‬ ‭segments‬ ‭(IgVH).‬ ‭These‬ ‭mutations‬ ‭occurs‬ ‭in‬ ‭somatic‬ ‭cells‬ ‭(non-‬ ‭reproductive).‬ ‭Mutated -‬‭gone through germinal centre‬ ‭Unmutated -‬‭hasn’t gone through germinal centre‬ ‭ lone‬ ‭IgVH‬ ‭region‬ ‭gene‬ ‭differs‬ ‭from‬‭germline‬‭sequence‬‭by‬ C C ‭ lone‬‭IgVH‬‭gene‬‭in‬‭CLL‬‭cells‬‭differs‬‭from‬‭germline‬‭sequence‬ ‭more‬ ‭than‬ ‭2%‬ ‭=‬ ‭mutated‬ ‭→‬ ‭means‬ ‭somatic‬‭mutation‬‭has‬ ‭by‬ ‭less‬ ‭than‬ ‭or‬ ‭equal‬ ‭to‬ ‭2%‬ ‭(same‬ ‭as‬ ‭saying‬ ‭Clone‬ ‭IgVH‬ ‭occurred in this gene (changes the sequence by >2%)‬ ‭region gene shows >98% homology (similarity))‬  ‭ ood‬‭prognosis‬‭(good‬‭chance‬‭of‬‭recovering‬‭from‬‭a‬‭disease)‬ ‭Bad prognosis‬ G ‭and account for‬‭50%‬‭of CLL cases‬ ‭ rogression‬ ‭requiring‬ ‭treatment‬ ‭after‬‭10-20‬‭years‬‭→‬‭more‬ P P ‭ rogression‬ ‭requiring‬ ‭treatment‬ ‭after‬ ‭2-5‬ ‭years‬ ‭→‬ ‭more‬ ‭indolent‬ ‭(slow‬ ‭progressing‬ ‭disease‬ ‭-‬ ‭doesn’t‬ ‭require‬ ‭aggressive‬ ‭and‬ ‭faster‬ ‭progression‬ ‭of‬ ‭disease‬ ‭→‬ ‭requires‬ ‭treatment for longer period of time)‬ ‭treatment a lot sooner‬ ‭ hronic‬ ‭Myeloid‬ ‭Leukaemia‬ ‭(CML)‬ ‭is‬ ‭a‬ ‭type‬ ‭of‬ ‭leukaemia,‬ ‭a‬ ‭cancer‬ ‭of‬ ‭the‬ ‭blood‬ ‭and‬ ‭bone‬ ‭marrow,‬ ‭characterised‬ ‭by‬ ‭the‬ C ‭abnormal and uncontrolled growth of myeloid cells.‬ ‭Pathophysiology:‬‭massive myeloid hyperplasia refers‬‭to the excessive production of myeloid cells in the bone marrow.‬ ‭Accumulation of immature and mature myeloid cells in both the blood and bone marrow contributes to the disease.‬ ‭Epidemiology:‬‭CML can affect individuals of both sexes,‬‭the most common age of onset is between 40 and 60 years.‬ ‭Risk‬‭Factors:‬‭prior‬‭irradiation‬‭has‬‭been‬‭associated‬‭with‬‭an‬‭increased‬‭incidence‬‭of‬‭CML,‬‭however‬‭CML‬‭is‬‭not‬‭significantly‬‭more‬ ‭frequent in monozygotic twins, suggesting that genetic factors alone may not be the primary cause.‬ ‭Disease Phases:‬ ‭Chronic Phase:‬‭This is the initial phase and is characterised‬‭by slow, asymptomatic growth of abnormal myeloid cells.‬ ‭Accelerated‬ ‭Phase:‬ ‭In‬ ‭this‬ ‭phase,‬ ‭the‬ ‭abnormal‬ ‭cells‬ ‭start‬ ‭to‬ ‭grow‬ ‭and‬ ‭divide‬ ‭more‬ ‭rapidly,‬ ‭leading‬ ‭to‬ ‭symptomatic‬ ‭manifestations.‬ ‭Blast‬ ‭Crisis‬ ‭(Acute‬ ‭Phase):‬ ‭This‬ ‭is‬ ‭an‬ ‭aggressive‬ ‭phase‬ ‭where‬‭the‬‭majority‬‭of‬‭cells‬‭in‬‭the‬‭bone‬‭marrow‬‭are‬‭immature‬‭blast‬ ‭cells. It resembles acute leukaemia and progresses rapidly.‬ ‭Genetic‬ ‭Mutation:‬ ‭The‬ ‭primary‬ ‭cause‬ ‭of‬ ‭CML‬ ‭is‬ ‭a‬ ‭specific‬ ‭genetic‬ ‭mutation‬ ‭known‬ ‭as‬ ‭the‬ ‭Philadelphia‬ ‭chromosome‬ ‭(Ph‬ ‭chromosome).‬ ‭The‬ ‭Philadelphia‬ ‭chromosome‬ ‭results‬ ‭from‬ ‭a‬ ‭reciprocal‬ ‭translocation‬ ‭between‬ ‭chromosomes‬ ‭9‬ ‭and‬ ‭22‬ ‭[t(9;22)],‬‭leading‬‭to‬‭the‬‭fusion‬‭of‬‭the‬‭BCR‬‭(breakpoint‬‭cluster‬‭region)‬‭gene‬‭on‬‭chromosome‬‭22‬‭with‬‭the‬‭ABL‬‭(Abelson‬‭murine‬ ‭leukemia‬‭viral‬‭oncogene‬‭homolog‬‭1)‬‭gene‬‭on‬‭chromosome‬‭9.‬‭This‬‭fusion‬‭gene‬‭is‬‭called‬‭BCR-ABL1.‬‭In‬‭light‬‭microscopy,‬‭dividing‬ ‭cells‬ ‭in‬ ‭95%‬ ‭of‬ ‭cases.‬ ‭BCR-ABL1‬‭Oncogene:‬‭The‬‭BCR-ABL1‬‭fusion‬‭gene‬‭produces‬‭a‬‭constitutively‬‭active‬‭tyrosine‬‭kinase‬‭that‬ ‭promotes uncontrolled cell proliferation and inhibits apoptosis. This aberrant kinase activity is a key driver of CML.‬ F‭ indings on FBC, blood film and special tests‬ ‭Findings‬ ‭on‬ ‭FBC:‬ ‭neutrophil‬ ‭leucocytosis‬ ‭(elevated‬ ‭WBC‬ ‭count),‬ ‭immature‬ ‭cells‬ ‭mainly‬ ‭myelocytes‬ ‭circulating‬ ‭in‬ ‭the‬ ‭peripheral blood, increase in circulating basophils, anaemia‬ ‭Findings‬ ‭on‬ ‭bone‬ ‭marrow‬ ‭biopsy:‬ ‭hypercellular,‬ ‭increase‬ ‭in‬ ‭myeloid‬ ‭series‬ ‭(bone‬ ‭marrow‬ ‭and‬ ‭blood‬ ‭appear‬ ‭similar),‬ ‭cytogenetic analysis and molecular analysis to detect the BCR-ABL chromosome‬ ‭Blood film:‬‭both blast and mature cells (for acute,‬‭would not see mature)‬ T‭ reatment‬‭;‬‭targeted‬‭therapies,‬‭such‬‭as‬‭tyrosine‬‭kinase‬‭inhibitors‬‭(TKIs),‬‭are‬‭the‬‭mainstay‬‭of‬‭treatment‬‭for‬‭CML.‬‭These‬‭drugs‬ ‭specifically‬ ‭target‬ ‭the‬ ‭BCR-ABL1‬ ‭tyrosine‬ ‭kinase,‬‭inhibiting‬‭its‬‭activity‬‭and‬‭slowing‬‭down‬‭or‬‭stopping‬‭the‬‭progression‬‭of‬‭the‬ ‭disease.‬ ‭Imatinib‬‭is‬‭a‬‭first-generation‬‭tyrosine‬‭kinase‬‭inhibitor‬‭(TKI)‬‭that‬‭specifically‬‭targets‬‭the‬‭BCR-ABL‬‭kinase,‬‭which‬‭is‬‭responsible‬ ‭for‬‭the‬‭abnormal‬‭growth‬‭in‬‭CML.‬‭It‬‭works‬‭by‬‭inhibiting‬‭the‬‭tyrosine‬‭kinase‬‭activity‬‭of‬‭the‬‭BCR-ABL‬‭fusion‬‭protein.‬‭While‬‭not‬ ‭considered‬ ‭a‬ ‭cure,‬ ‭imatinib‬ ‭can‬ ‭induce‬ ‭haematological‬ ‭remission‬ ‭(normalising‬ ‭blood‬ ‭counts),‬ ‭cytogenetic‬ ‭remission‬ ‭(elimination‬‭or‬‭reduction‬‭of‬‭leukaemia‬‭cells‬‭with‬‭the‬‭Philadelphia‬‭chromosome),‬‭molecular‬‭remission‬‭(undetectable‬‭levels‬‭of‬ ‭BCR-ABL at the molecular level using PCR).‬ ‭Resistance‬ ‭to‬ ‭imatinib‬ ‭can‬ ‭occur‬ ‭through‬ ‭various‬ ‭mechanisms,‬ ‭including‬ ‭either‬ ‭de‬ ‭novo‬ ‭or‬ ‭acquired:‬ ‭point‬ ‭mutations‬ ‭in‬ ‭BCR-ABL‬ ‭gene‬ ‭preventing‬ ‭imatinib‬ ‭from‬ ‭inhibiting‬ ‭kinase‬ ‭activity,‬ ‭BCR-ABL‬ ‭gene‬ ‭amplification/BCR-ABL‬ ‭independent‬ ‭mechanisms‬‭or activation of the‬‭SRC family kinases‬‭.‬ S‭ econd-Generation‬‭Tyrosine‬‭Kinase‬‭Inhibitors‬‭are‬‭used‬‭on‬‭those‬‭who‬‭develop‬‭resistance‬‭to‬‭or‬‭cannot‬‭tolerate‬‭imatinib.‬‭The‬ ‭choice‬ ‭of‬ ‭TKI‬ ‭depends‬ ‭on‬ ‭factors‬ ‭such‬ ‭as‬ ‭the‬ ‭patient's‬ ‭response,‬ ‭side‬ ‭effects,‬ ‭and‬ ‭the‬ ‭specific‬ ‭mutations‬ ‭present‬ ‭in‬ ‭the‬ ‭BCR-ABL gene. Regular monitoring and adjustment of treatment are crucial to manage the disease effectively.‬  ‭ asatinib‬‭:‬ ‭A‬ ‭dual‬ ‭SRC-ABL‬ ‭kinase‬ ‭inhibitor‬ ‭that‬ ‭targets‬ ‭both‬ ‭active‬ ‭conformations‬ ‭of‬ ‭ABL‬ ‭and‬ ‭SRC,‬ ‭which‬ ‭are‬ ‭structurally‬ D ‭similar. About 300-fold higher potency against native BCR-ABL compared to imatinib, making it very effective.‬ ‭Nilotinib:‬ ‭Specifically‬ ‭designed‬ ‭to‬ ‭have‬ ‭a‬ ‭higher‬ ‭binding‬ ‭affinity‬ ‭for‬ ‭BCR-ABL‬ ‭kinase‬ ‭compared‬ ‭to‬ ‭imatinib.‬ ‭Modified‬ ‭from‬ ‭imatinib‬‭to‬‭enhance‬‭BCR-ABL‬‭kinase‬‭binding‬‭activity.‬‭Less‬‭prone‬‭to‬‭resistance‬‭development‬‭compared‬‭to‬‭imatinib‬‭due‬‭to‬‭its‬ ‭increased potency. An option for CML patients who do not respond well to imatinib.‬ ‭Ponatinib:‬ ‭a‬ ‭multitargeted‬ ‭kinase‬ ‭inhibitor‬‭that‬‭is‬‭active‬‭against‬‭all‬‭known‬‭BCR-ABL‬‭mutants,‬‭including‬‭the‬‭T315I‬‭mutation,‬ ‭which is particularly challenging to treat with other TKIs.‬ ‭IMMUNOLOGICAL BASIS FOR TRANSPLANTATION‬ T‭ ransplantation‬‭is‬‭the‬‭most‬‭effective‬‭treatment‬‭for‬‭end‬‭stage‬‭organ‬‭failure,‬‭although‬‭transplanted‬‭organ‬‭survival‬‭is‬‭limited‬ ‭by‬‭immune‬‭rejection;‬‭the‬‭short‬‭term‬‭outcomes‬‭are‬‭excellent,‬‭and‬‭long‬‭term‬‭outcomes‬‭have‬‭changed‬‭very‬‭little‬‭over‬‭the‬‭past‬ ‭few decades - rejection is due to T-cell mediated rejection and/or antibody-mediated rejection.‬ ‭‬ ‭1954‬ ‭=‬ ‭first‬ ‭successful‬ ‭living-related‬‭kidney‬‭transplant‬‭between‬‭identical‬‭twin‬‭Herrick‬‭brothers,‬‭Dr.‬‭Joseph‬‭Murray’s‬ ‭team‬ ‭‬ ‭1962 = first cadaveric kidney transplant, Dr. Joseph Murray‬ ‭‬ ‭1963 = first lung transplant, Dr. James Hardy‬ ‭‬ ‭1967 = first liver transplant , Dr. Thomas Starz‬ ‭‬ ‭1967 = first heart transplant, Dr. Christiaan Neethling Barnard‬ ‭Transplanted organ survival is limited by the side effects of long-term immunosuppressive regimens‬ ‭‬ ‭Infection: serious bacterial, fungal and viral infections‬ ‭‬ ‭Malignancies - skin cancer, most common in kidney and liver transplantation‬ ‭‬ ‭Neurotoxicity: apparent months or years‬ ‭‬ ‭Diabetes‬ ‭‬ ‭CVS events‬ ‭‬ ‭Metabolic syndrome - hyperlipidaemia, diabetes, HTN‬ ‭Majority of rejection occurs within the first 6 months of transplantation, as this is when immunosuppression is highest.‬ ‭Recommendation: no elective dental work within these 6 months.‬ ‭Malignancy is the tell-tale sign of immunosuppression - skin cancer is the most common.‬ ‭ ejection - the transplant recipient’s immune system attacks the transplanted organ‬‭over three stages:‬ R ‭Hyperacute‬ ‭rejection:‬ ‭minutes‬ ‭to‬ ‭hours‬‭-‬‭the‬‭most‬‭rapid‬‭and‬‭severe‬‭form‬‭of‬‭rejection,‬‭caused‬‭by‬‭pre-existing‬‭antibodies‬‭in‬ ‭the‬‭recipient’s‬‭blood‬‭that‬‭react‬‭against‬‭antigens‬‭on‬‭the‬‭donor‬‭organ;‬‭anti-donor‬‭antibodies‬‭against‬‭ABO/HLA/other‬‭antigens‬ ‭causes‬ ‭complement‬ ‭activation,‬ ‭thrombosis,‬ ‭leukocyte‬ ‭inflammation,‬ ‭endothelial‬ ‭damage,‬ ‭leading‬ ‭to‬ ‭immediate‬ ‭and‬ ‭irreversible‬ ‭damage‬ ‭to‬ ‭the‬ ‭transplanted‬ ‭organ.‬ ‭This‬ ‭is‬ ‭however‬ ‭rare‬ ‭these‬ ‭days‬ ‭due‬ ‭to‬ ‭extensive‬ ‭pre-transplant‬ ‭testing‬‭to‬ ‭identify donors.‬ ‭Acute‬‭rejection:‬‭days‬‭to‬‭12‬‭months‬‭-‬‭occurs‬‭as‬‭the‬‭recipient’s‬‭immune‬‭system‬‭recognises‬‭the‬‭transplanted‬‭organ‬‭as‬‭foreign,‬ ‭mounting‬ ‭an‬‭immune‬‭response‬‭against‬‭it‬‭-‬‭T‬‭cell‬‭mediated‬‭alloresponse.‬‭It‬‭is‬‭characterised‬‭by‬‭inflammation‬‭and‬‭damage‬‭to‬ ‭the transplanted tissue and is often treated with immunosuppressive meds.‬ ‭Chronic‬‭rejection:‬‭months‬‭or‬‭years‬‭after‬‭and‬‭is‬‭characterised‬‭by‬‭fibrosis‬‭and‬‭vascular‬‭abnormalities.‬‭De‬‭novo‬‭donor‬‭specific‬ ‭antibodies‬ ‭(dnDSA)‬ ‭is‬ ‭an‬ ‭important‬ ‭risk‬ ‭factor.‬ ‭It‬ ‭involves‬ ‭slow‬ ‭deterioration‬ ‭of‬ ‭the‬ ‭organ’s‬ ‭function‬ ‭-‬ ‭often‬ ‭resistant‬ ‭to‬ ‭treatment with immunosuppressive drugs → can lead to organ failure.‬ T‭ ‬‭cells‬‭are‬‭central‬‭to‬‭the‬‭process‬‭of‬‭transplantation‬‭rejection‬‭through‬‭allorecognition‬‭of‬‭foreign‬‭antigens.‬‭Both‬‭CD4‬‭and‬‭CD8‬‭T‬ ‭cells‬‭are‬‭involved.‬‭Both‬‭T‬‭cells‬‭and‬‭B‬‭cells‬‭play‬‭a‬‭role‬‭in‬‭acute‬‭and‬‭chronic‬‭rejection.‬‭These‬‭alloreactive‬‭T‬‭cells‬‭can‬‭recognise‬ ‭and respond to antigens on transplanted organs or tissues that are different from the recipient’s own antigens.‬ ‭Allorecognition:‬‭ability‬‭of‬‭an‬‭organism‬‭to‬‭distinguish‬‭its‬‭own‬‭cells‬‭and‬‭tissues‬‭from‬‭those‬‭of‬‭another‬‭from‬‭the‬‭same‬‭species‬ ‭i.e. how it responds to foreign antigens.‬  ‭ onor‬‭organ‬‭→‬‭recipient‬‭lymph‬‭node‬‭→‬‭CD8+‬‭T‬‭cell‬‭+‬‭dendritic‬‭cells‬‭+‬‭CD4+‬‭T‬‭cell‬‭→‬‭release‬‭cytokines‬‭→‬‭clonal‬‭expansion‬ D ‭and‬‭additional‬‭cytokine‬‭and‬‭chemokine‬‭production‬‭→‬‭differentiated‬‭macrophages‬‭+‬‭B-cell‬‭antibody‬‭production‬‭→‬‭activated‬‭T‬ ‭cells → acute rejection‬ ‭Organ → T cells → cytokines → B cells → macrophages → acute rejection.‬ T‭ cell activation signals‬ ‭Signal 1: antigen specific, T cell receptors recognise MHC-allo-peptide complex (CD4 binds MHC 2 and CD8 binds MHC1)‬ ‭Signal 2: antigen-non-specific, binding of co-stimulatory molecules (CD28-B7, CD80/CD86, CD40L-CD40 pathways)‬ ‭Signal 3: cytokine stimulation (IFN-gamma)‬ S‭ ignal 2 and 3 are critical in rejection.‬ ‭Signal 1 and 2 are at least needed for T cell activation.‬ T‭ he‬‭diversity‬‭of‬‭the‬‭alpha-beta‬‭T‬‭cell‬‭receptor‬‭(TCR)‬‭is‬‭essential‬‭for‬‭the‬‭immune‬‭system‬‭to‬‭effectively‬‭recognize‬‭and‬‭respond‬ ‭to a‬‭vast array of antigens‬‭.‬ ‭Expression‬ ‭in‬ ‭Human‬ ‭Peripheral‬ ‭Blood‬ ‭T‬ ‭Cells‬‭:‬ ‭Over‬ ‭95%‬ ‭of‬ ‭human‬ ‭peripheral‬ ‭blood‬ ‭T‬ ‭cells‬ ‭express‬ ‭the‬ ‭alpha-beta‬ ‭TCR‬ ‭complex. This complex consists of two protein chains, the alpha chain, and the beta chain.‬ ‭Overall‬ ‭TCR‬ ‭Diversity:‬ ‭the‬ ‭diversity‬ ‭of‬ ‭the‬ ‭TCR‬ ‭is‬ ‭immense,‬ ‭with‬ ‭approximately‬ ‭2.5‬ ‭x‬ ‭10^7‬ ‭(25‬ ‭million)‬ ‭different‬ ‭TCRs‬ ‭estimated to exist in humans.‬ ‭Genetic‬ ‭Basis‬ ‭of‬ ‭Diversity:‬ ‭The‬ ‭diversity‬ ‭of‬ ‭the‬ ‭TCR‬ ‭is‬ ‭primarily‬ ‭generated‬ ‭through‬ ‭genetic‬ ‭mechanisms‬ ‭during‬ ‭T‬ ‭cell‬ ‭development.‬‭This‬‭involves‬‭the‬‭rearrangement‬‭of‬‭gene‬‭segments‬‭encoding‬‭the‬‭TCR.‬‭The‬‭TCR‬‭genes‬‭are‬‭composed‬‭of‬‭variable‬ ‭(V),‬ ‭diversity‬ ‭(D),‬ ‭and‬ ‭joining‬ ‭(J)‬ ‭gene‬ ‭segments‬‭.‬ ‭The‬ ‭combination‬ ‭of‬ ‭different‬ ‭V,‬ ‭D,‬ ‭and‬ ‭J‬ ‭segments‬ ‭contributes‬ ‭to‬ ‭the‬ ‭diversity of TCRs.‬ ‭N-Region‬ ‭Diversity:‬ ‭The‬ ‭diversity‬ ‭is‬ ‭further‬ ‭increased‬ ‭by‬ ‭the‬ ‭addition‬ ‭of‬‭non-templated‬‭nucleotides,‬‭known‬‭as‬‭N‬‭regions‬‭,‬ ‭during the gene rearrangement process. This N-region diversity adds extra variability to the TCR sequence.‬ ‭CDR3‬‭Region‬‭and‬‭Diversity:‬‭The‬‭complementarity-determining‬‭region‬‭3‬‭(CDR3)‬‭is‬‭a‬‭highly‬‭variable‬‭region‬‭within‬‭the‬‭TCR.‬‭It‬‭is‬ ‭formed‬‭by‬‭the‬‭junction‬‭of‬‭the‬‭V,‬‭D,‬‭and‬‭J‬‭gene‬‭segments‬‭and‬‭the‬‭added‬‭N‬‭regions.‬‭The‬‭CDR3‬‭region‬‭is‬‭particularly‬‭important‬ ‭for antigen recognition, as it directly interacts with the peptide-MHC complex.‬  T‭ he‬ ‭Major‬ ‭Histocompatibility‬ ‭Complex‬ ‭(MHC)‬‭,‬ ‭also‬‭known‬‭as‬‭the‬‭Human‬‭Leukocyte‬‭Antigen‬‭(HLA)‬‭system‬‭in‬‭humans,‬‭is‬‭a‬ ‭crucial‬ ‭genetic‬ ‭system‬ ‭involved‬ ‭in‬ ‭immune‬ ‭responses,‬ ‭particularly‬ ‭in‬ ‭the‬ ‭recognition‬ ‭and‬ ‭rejection‬ ‭of‬ ‭foreign‬ ‭or‬ ‭non-self‬ ‭tissues.‬ ‭Genetic Loci and Chromosome Location:‬‭The MHC is a‬‭genomic region located on chromosome 6 in humans.‬ ‭Role‬ ‭in‬ ‭Tissue‬ ‭Rejection:‬ ‭MHC‬ ‭molecules‬ ‭are‬ ‭essential‬ ‭for‬ ‭the‬ ‭immune‬ ‭system's‬ ‭ability‬ ‭to‬ ‭distinguish‬ ‭between‬ ‭self‬ ‭and‬ ‭non-self‬ ‭tissues.‬ ‭Mismatch‬ ‭of‬ ‭MHC‬ ‭molecules‬ ‭between‬ ‭donor‬ ‭and‬ ‭recipient‬ ‭is‬ ‭a‬ ‭significant‬ ‭factor‬ ‭in‬ ‭the‬ ‭rejection‬ ‭of‬ ‭transplanted organs or tissues.‬ ‭Polymorphic‬‭Cell‬‭Surface‬‭Structures:‬‭MHC‬‭molecules‬‭are‬‭highly‬‭polymorphic,‬‭meaning‬‭there‬‭is‬‭a‬‭significant‬‭variation‬‭in‬‭the‬ ‭gene‬ ‭sequences‬ ‭that‬ ‭encode‬ ‭these‬ ‭molecules‬ ‭among‬ ‭individuals.‬ ‭This‬ ‭polymorphism‬ ‭contributes‬ ‭to‬ ‭the‬ ‭diversity‬ ‭of‬ ‭MHC‬ ‭molecules, allowing the immune system to recognize a wide range of antigens.‬ ‭MHC Class I and Class II:‬‭MHC molecules are categorized‬‭into two main classes: MHC class I and MHC class II.‬ ‭MHC Class I (HLA-A, B, C):‬‭These molecules are found‬‭on the surface of almost all nucleated cells.‬ ‭MHC‬‭Class‬‭II‬‭(HLA-DR,‬‭DP,‬‭DQ,‬‭DO,‬‭DM):‬‭These‬‭molecules‬‭are‬‭primarily‬‭expressed‬‭on‬‭the‬‭surface‬‭of‬‭antigen-presenting‬‭cells‬ ‭(APCs) such as macrophages, B cells, and dendritic cells.‬ ‭Antigen Presentation: MHC molecules play a crucial role in presenting antigens to T cells‬‭.‬ ‭Potential donor siblings‬ ‭When‬‭considering‬‭organ‬‭or‬‭tissue‬‭transplantation,‬‭the‬‭compatibility‬‭of‬‭the‬‭donor's‬‭Human‬‭Leukocyte‬‭Antigen‬‭(HLA)‬‭with‬‭the‬ ‭recipient's‬ ‭HLA‬ ‭is‬ ‭a‬ ‭crucial‬ ‭factor‬ ‭in‬ ‭minimizing‬ ‭the‬ ‭risk‬ ‭of‬ ‭transplant‬ ‭rejection.‬ ‭HLA‬ ‭molecules‬ ‭are‬ ‭highly‬ ‭polymorphic,‬ ‭meaning‬ ‭there‬ ‭is‬ ‭a‬ ‭wide‬ ‭variety‬ ‭of‬ ‭HLA‬ ‭alleles‬ ‭within‬ ‭the‬ ‭human‬ ‭population.‬ ‭The‬ ‭more‬ ‭closely‬ ‭matched‬ ‭the‬ ‭donor‬ ‭and‬ ‭recipient‬ ‭HLA,‬ ‭the‬ ‭lower‬ ‭the‬ ‭likelihood‬ ‭of‬ ‭rejection.‬ ‭Siblings‬ ‭are‬ ‭potential‬ ‭donors‬ ‭because‬ ‭there‬ ‭is‬ ‭a‬‭higher‬‭likelihood‬‭of‬ ‭sharing‬‭HLA‬‭alleles‬‭with‬‭siblings‬‭due‬‭to‬‭the‬‭genetic‬‭similarities‬‭inherited‬‭from‬‭common‬‭parents.‬‭If‬‭a‬‭sibling‬‭is‬‭a‬‭full‬‭match‬ ‭or‬‭a‬‭close‬‭match‬‭in‬‭terms‬‭of‬‭HLA‬‭compatibility,‬‭it‬‭can‬‭enhance‬‭the‬‭chances‬‭of‬‭a‬‭successful‬‭transplant.‬‭The‬‭probability‬‭that‬‭2‬ ‭siblings will have the same HLA allele is 25% (0.5 x 0.5).‬ ‭ irect‬‭allorecognition‬‭occurs‬‭when‬‭recipient‬‭T‬‭cells‬‭directly‬‭recognise‬‭donor‬‭MHCs‬‭on‬‭the‬‭surface‬‭of‬‭donor‬‭APCs‬‭within‬‭the‬ D ‭transplanted‬ ‭organ.‬ ‭Donor‬ ‭APCs‬ ‭migrate‬ ‭from‬ ‭the‬ ‭transplanted‬ ‭organ‬ ‭to‬ ‭the‬ ‭recipient’s‬ ‭lymphoid‬ ‭tissues,‬ ‭where‬ ‭T‬ ‭cells‬ ‭recognise‬ ‭the‬ ‭foreign‬‭MHC‬‭molecules‬‭on‬‭the‬‭donor‬‭APCs.‬‭This‬‭often‬‭results‬‭in‬‭a‬‭strong‬‭and‬‭rapid‬‭immune‬‭response‬‭against‬ ‭the transplanted organ →‬‭acute rejection‬‭(the primary‬‭pathway for acute rejection).‬ ‭Indirect‬ ‭allorecognition‬ ‭occurs‬ ‭when‬ ‭recipient‬ ‭T‬ ‭cells‬ ‭recognise‬ ‭donor‬ ‭antigens‬ ‭that‬ ‭have‬ ‭already‬ ‭been‬ ‭processed‬‭by‬‭the‬ ‭recipient’s‬ ‭APCs‬ ‭(donor‬ ‭antigens‬ ‭are‬ ‭presented‬ ‭as‬ ‭peptides‬ ‭to‬ ‭the‬ ‭TCR).‬ ‭Recipient‬ ‭APCs‬ ‭take‬ ‭up‬ ‭donor‬ ‭antigens‬ ‭after‬ ‭transplantation,‬‭processed‬‭as‬‭peptides,‬‭then‬‭presented‬‭to‬‭recipient‬‭T‬‭cells,‬‭which‬‭recognise‬‭these‬‭antigens‬‭are‬‭non-self.‬‭This‬ ‭is associated with‬‭chronic rejection‬‭- less immediate,‬‭but can be more persistent than direct allorecognition.‬ ‭Semi-direct‬ ‭allorecognition‬ ‭is‬ ‭a‬ ‭hybrid‬ ‭pathway‬ ‭combining‬ ‭direct‬ ‭and‬ ‭indirect.‬ ‭Donor‬ ‭APCs‬ ‭release‬ ‭MHC‬ ‭peptides‬ ‭into‬ ‭circulation,‬ ‭which‬ ‭are‬ ‭taken‬ ‭up‬ ‭by‬ ‭recipient‬‭APCs‬‭and‬‭presented‬‭to‬‭recipient‬‭T‬‭cells‬‭.‬‭This‬‭often‬‭happens‬‭when‬‭donor‬‭APCs‬ ‭aren’t‬ ‭able‬ ‭to‬ ‭attach‬ ‭to‬ ‭TCRs‬ ‭due‬ ‭to‬ ‭physical‬ ‭barriers.‬ ‭It‬ ‭can‬ ‭contribute‬‭to‬‭both‬‭acute‬‭and‬‭chronic‬‭rejection‬‭→‬‭essentially‬ ‭allows‬‭recognition‬‭and‬‭response‬‭to‬‭donor‬‭antigens‬‭indirectly,‬‭when‬‭direct‬‭interactions‬‭between‬‭donor‬‭and‬‭recipient‬‭APCs‬‭are‬ ‭limited physically.‬ ‭ irect: donor APCs + donor MHC + donor antigen → T cells‬ D ‭Indirect: recipient APC + recipient MHC + donor antigen → T cells‬ ‭Semi-direct: recipient APC + donor MHC + donor antigen → T cells‬ ‭Immunosuppressive agents in transplantation‬‭(don’t‬‭have to know in detail)‬ ‭‬ ‭Deletion/Inhibition of Alloreactive T Cells:‬ ‭○‬ ‭Thymoglobulin:‬ ‭An‬ ‭antibody‬ ‭preparation‬ ‭that‬ ‭depletes‬ ‭T‬ ‭cells‬ ‭and‬ ‭other‬ ‭immune‬ ‭cells‬ ‭to‬ ‭reduce‬ ‭the‬ ‭recipient's immune response.‬ ‭○‬ ‭Tacrolimus‬ ‭(FK506)‬ ‭and‬ ‭Cyclosporine:‬ ‭Calcineurin‬ ‭inhibitors‬ ‭that‬ ‭inhibit‬ ‭T‬ ‭cell‬ ‭activation‬ ‭by‬ ‭blocking‬ ‭the‬ ‭production of interleukin-2 (IL-2).‬ ‭○‬ ‭Basiliximab: A monoclonal antibody that targets CD25 on activated T cells, reducing their activity.‬ ‭○‬ ‭Mycophenolate‬ ‭Mofetil‬ ‭(MMF):‬ ‭Inhibits‬ ‭the‬ ‭proliferation‬ ‭of‬ ‭T‬ ‭and‬ ‭B‬ ‭cells‬ ‭by‬ ‭blocking‬ ‭the‬ ‭synthesis‬ ‭of‬ ‭nucleotides.‬ ‭○‬ ‭Rapamycin: Inhibits T cell proliferation by targeting the mammalian target of rapamycin (mTOR) pathway.‬ ‭○‬ ‭Belatacept‬‭(CTLA4-Ig):‬‭A‬‭costimulation‬‭blockade‬‭agent‬‭that‬‭interferes‬‭with‬‭T‬‭cell‬‭activation‬‭by‬‭binding‬‭to‬‭CD80‬ ‭and CD86 on antigen-presenting cells.‬ ‭‬ ‭Deletion of B Cells: Rituximab: A monoclonal antibody that targets CD20 on B cells, leading to their depletion.‬ ‭‬ ‭B-Cell-T-Cell‬‭Interactions:‬‭Alemtuzumab:‬‭A‬‭monoclonal‬‭antibody‬‭that‬‭targets‬‭CD52,‬‭which‬‭is‬‭present‬‭on‬‭both‬‭B‬‭and‬‭T‬ ‭cells, leading to their depletion.‬ ‭‬ ‭TNF‬‭Inhibition:‬‭Etanercept:‬‭An‬‭inhibitor‬‭of‬‭tumor‬‭necrosis‬‭factor‬‭(TNF),‬‭which‬‭is‬‭involved‬‭in‬‭inflammation‬‭and‬‭immune‬ ‭responses.‬ ‭‬ ‭IL-6‬‭Inhibition:‬‭Tocilizumab:‬‭An‬‭antibody‬‭that‬‭inhibits‬‭interleukin-6‬‭(IL-6)‬‭signaling,‬‭which‬‭is‬‭involved‬‭in‬‭inflammation‬ ‭and immune responses.‬ ‭Balance‬ ‭between‬ ‭activation‬ ‭and‬ ‭regulation;‬ ‭the‬ ‭goal‬ ‭is‬ ‭long‬ ‭term‬ ‭transplant‬ ‭organ‬ ‭acceptance‬ ‭in‬ ‭the‬ ‭absence‬ ‭of‬ ‭immunosuppressive‬ ‭therapy‬ → ‭ ‬ ‭transplant‬ ‭tolerance.‬ ‭Transplant‬ ‭tolerance‬ ‭is‬ ‭when‬ ‭the‬ ‭immune‬ ‭system‬ ‭does‬ ‭not‬ ‭attack‬ ‭transplanted‬‭grafts,‬‭but‬‭also‬‭remains‬‭capable‬‭of‬‭responding‬‭to‬‭pathogenic‬‭microorganisms‬‭and‬‭other‬‭antigens‬‭i.e.‬‭there‬‭is‬‭a‬ ‭balance‬ ‭between‬ ‭allo-reactive‬ ‭T‬‭cells‬‭and‬‭regulatory‬‭T‬‭cells.‬‭Alloreactive‬‭T‬‭cells‬‭are‬‭the‬‭T‬‭cells‬‭that‬‭recognize‬‭alloantigens‬‭-‬ ‭presented‬‭on‬‭MHC‬‭→‬‭initiate‬‭immune‬‭response‬‭against‬ ‭transplanted‬‭organ,‬‭and‬‭regulatory‬‭T‬‭Cells‬‭(Treg‬‭Cells)‬‭are‬‭the‬‭T‬‭cells‬ ‭with immunosuppressive properties. When:‬ ‭‬ ‭Alloreactive T cells > reg T cells → transplant rejection‬ ‭‬ ‭Reg T cells > alloreactive T cells → immunosuppression to all antigens‬ ‭Cell based immune cell therapy in transplantation‬ ‭‬ ‭Bone marrow cells:‬‭mixed and full haematopoietic donor‬‭chemierism (kidney transplants)‬ ‭‬ ‭Tolerogenic dendritic cells:‬‭in kidney transplants‬ ‭‬ ‭Regulatory B cells:‬‭diabetic patients‬ ‭‬ ‭Regulatory T cells‬‭- the most attractive‬‭Foxp3+ T-regulatory‬‭cell therap‬‭y - kidney and liver transplantations‬ ‭ D4+CD25+Foxp3+ regulatory T cells (Tregs) play a critical role in immune regulation and tolerance.‬ C ‭Development‬‭and‬‭Induction:‬‭CD4+CD25+Foxp3+‬‭Tregs‬‭develop‬‭in‬‭the‬‭thymus‬‭as‬‭a‬‭subset‬‭of‬‭regulatory‬‭T‬‭cells‬‭,‬‭and‬‭they‬‭can‬ ‭also be induced‬‭peripherally‬‭from conventional‬‭CD4+‬‭T cells‬‭in response to certain environmental cues.‬ ‭Immune‬ ‭Homeostasis‬ ‭and‬ ‭Autoimmunity‬ ‭Prevention:‬ ‭Tregs‬ ‭are‬ ‭essential‬ ‭for‬ ‭maintaining‬ ‭immune‬ ‭homeostasis‬ ‭by‬ ‭suppressing excessive immune responses. They play a crucial role in‬‭preventing autoimmunity.‬ ‭Suppressing‬ ‭Transplant‬ ‭Rejection:‬ ‭Tregs‬ ‭are‬ ‭involved‬ ‭in‬ ‭suppressing‬ ‭transplant‬ ‭rejection‬ ‭by‬ ‭inhibiting‬ ‭the‬ ‭activation‬ ‭and‬ ‭function‬‭of‬‭alloreactive‬‭T‬‭cells‬‭that‬‭recognize‬‭antigens‬‭from‬‭the‬‭transplanted‬‭organ.‬‭Their‬‭suppressive‬‭activity‬‭helps‬‭dampen‬ ‭the immune response directed against the graft.‬ ‭Promoting‬‭Transplant‬‭Tolerance:‬‭Transplant‬‭tolerance‬‭involves‬‭the‬‭immune‬‭system‬‭accepting‬‭the‬‭transplanted‬‭organ‬‭without‬ ‭mounting‬ ‭an‬ ‭immune‬ ‭response‬ ‭against‬ ‭it.‬ ‭Tregs‬ ‭are‬ ‭critical‬ ‭for‬ ‭promoting‬ ‭transplant‬ ‭tolerance‬ ‭by‬ ‭dampening‬ ‭alloreactive‬ ‭responses and promoting an environment conducive to long-term acceptance of the graft.‬ ‭IPEX‬ ‭Syndrome:‬ ‭Immunodysregulation‬ ‭Polyendocrinopathy‬ ‭Enteropathy‬ ‭X-linked‬ ‭(IPEX)‬ ‭syndrome‬ ‭is‬ ‭a‬‭severe‬‭autoimmune‬ ‭disorder caused by‬‭mutations in the FOXP3 gene,‬‭which‬‭leads to dysfunctional Tregs.‬ ‭Experimental‬ ‭Evidence‬ ‭in‬ ‭Transplant‬ ‭Tolerance:‬ ‭Animal‬ ‭models‬ ‭of‬ ‭transplant‬ ‭tolerance‬ ‭have‬ ‭provided‬ ‭evidence‬ ‭for‬ ‭the‬ ‭importance‬ ‭of‬ ‭Foxp3+‬ ‭Tregs.‬ ‭Depletion‬ ‭experiments‬ ‭showed‬ ‭that‬ ‭the‬ ‭absence‬ ‭of‬ ‭Foxp3+‬ ‭Tregs‬ ‭abolished‬ ‭kidney‬ ‭graft‬ ‭tolerance‬‭.‬ ‭Donor‬ ‭antigen-specific‬ ‭Foxp3+‬ ‭Tregs‬ ‭were‬ ‭identified‬ ‭as‬ ‭key‬ ‭players‬ ‭in‬ ‭maintaining‬ ‭kidney‬ ‭tolerance‬ ‭in‬ ‭these‬ ‭models. Furthermore, their presence provided‬‭spontaneous‬‭acceptance of kidney allotransplant tolerance.‬ ‭Methods to Generate and Induce Foxp3+ Tregs:‬ ‭Various methods have been explored to generate and induce Foxp3+ Tregs, including:‬ ‭‬ ‭Direct‬ ‭Antigen-Expanded‬ ‭Tregs:‬ ‭Tregs‬ ‭can‬ ‭be‬ ‭expanded‬ ‭using‬‭antigens‬‭presented‬‭by‬‭donor‬‭antigen-presenting‬‭cells‬ ‭(APCs) and donor MHC molecules - focuses on antigens from the donor tissue‬ ‭‬ ‭Indirect‬ ‭Antigen-Expanded‬‭Tregs:‬‭Tregs‬‭can‬‭also‬‭be‬‭expanded‬‭using‬‭antigens‬‭presented‬‭by‬‭host‬‭APCs‬‭and‬‭host‬‭MHC‬ ‭molecules - approach is based on antigens from the recipient's own tissues.‬ ‭‬ ‭Polyclonal‬ ‭Expansion‬ ‭with‬ ‭Anti-CD3/CD28‬‭Beads:‬‭involves‬‭stimulating‬‭Tregs‬‭with‬‭anti-CD3‬‭and‬‭anti-CD28‬‭antibodies‬ ‭attached to beads.‬ ‭‬ ‭Isolation of Specific Tregs Using Tetramers composed of host MHC II and donor MHC‬ ‭‬ ‭CAR-Treg‬‭(Chimeric‬‭Antigen‬‭Receptor‬‭Tregs),‬‭HLA-A2‬‭specific:‬‭CARs‬‭are‬‭designed‬‭to‬‭promote‬‭immunosuppression‬‭and‬ ‭immune tolerance.‬ ‭‬ ‭Insertion of Allospecific TCR (T Cell Receptor): Transgenic TCR expression‬ ‭‬ ‭Donor antigen specific Foxp3+ Tregs‬ ‭FULL BLOOD COUNT, BLOOD FILM AND COAGULATION‬ ‭Normal blood film‬ ‭ BC‬‭: pale centre and red rim‬ R ‭Neutrophil‬‭: RNA is purple and cytoplasm pink (even‬‭though it looks purple) - has granules‬ T‭ he‬‭physiological production of red blood cells (erythropoiesis)‬‭is a dynamic and‬‭tightly regulated‬‭process that involves‬ ‭various stages of cell differentiation and interaction with the microenvironment.‬ ‭The process begins with a‬‭multipotent hematopoietic‬‭stem cell‬‭, which can give rise to various blood cell‬‭lineages. When the‬ ‭stem cell‬‭commits‬‭to the erythroid program, it becomes‬‭an‬‭erythroid progenitor.‬ ‭After commitment to the erythroid lineage, several divisions later, the cells start‬‭expressing the erythroid‬‭program‬‭. This‬ ‭involves the activation of specific genes that drive the cells toward becoming red blood cells. The committed cells undergo‬ ‭further differentiation into erythroid precursor cells.‬ ‭As these cells mature, they eventually‬‭lose their‬‭nucleus‬‭during the‬‭reticulocyte stage‬‭.‬‭Reticulocytes‬‭are‬‭immature red‬ ‭blood cells‬‭that still contain some cellular remnants,‬‭such as ribosomal RNA.‬‭The loss of the nucleus‬‭in‬‭reticulocytes is a‬ ‭critical step in the maturation of red blood cells. Mature red blood cells are‬‭enucleated‬‭, allowing them‬‭to have more space to‬ ‭carry oxygen and increasing their flexibility to navigate through narrow blood vessels.‬ ‭During ontogeny (the development of an organism‬‭),‬‭erythropoiesis occurs in distinct anatomic sites, such as the yolk sac,‬ ‭liver, and bone marrow, at different stages of development. Each of these sites provides a unique microenvironment that‬ ‭influences the development of erythroid cells. The microenvironment includes interactions with stromal cells, hematopoietic‬ ‭accessory cells, and the extracellular matrix. These interactions play a crucial role in supporting and regulating erythropoiesis‬ ‭- and development is influenced by cytokines.‬ ‭Normal bone marrow‬ E‭ rythroid Precursor Cell Compartment and Cellular Dynamics:‬ ‭Erythropoiesis‬ ‭involves‬ ‭the‬ ‭differentiation‬ ‭and‬ ‭maturation‬ ‭of‬ ‭erythroid‬‭precursor‬‭cells,‬‭ultimately‬‭leading‬‭to‬‭the‬‭production‬‭of‬ ‭red‬ ‭blood‬ ‭cells.‬ ‭Gene‬ ‭activity‬ ‭during‬ ‭erythroid‬ ‭maturation‬ ‭is‬ ‭dominated‬ ‭by‬ ‭the‬ ‭expression‬ ‭of‬ ‭globin‬ ‭genes‬‭,‬ ‭constituting‬ ‭the‬ ‭majority of protein at the reticulocyte stage (95%).‬ ‭Red‬‭Cell‬‭Production‬‭and‬‭Cellular‬‭Dynamics:‬‭In‬‭the‬‭adult‬‭marrow,‬ ‭approximately‬‭3‬‭x‬‭10^9‬‭new‬‭red‬‭blood‬‭cells‬‭per‬‭kilogram‬‭per‬‭day‬ ‭are‬ ‭produced,‬ ‭accounting‬ ‭for‬ ‭1%‬ ‭of‬ ‭the‬ ‭total‬ ‭red‬ ‭cell‬ ‭mass.‬ ‭Successful‬ ‭red‬ ‭cell‬ ‭production‬ ‭requires‬ ‭an‬ ‭intact‬ ‭microenvironment‬‭and‬‭an‬‭adequate‬‭supply‬‭of‬‭iron,‬‭essential‬‭for‬ ‭haemoglobin synthesis.‬  ‭ aemoglobin‬ ‭Synthesis:‬ ‭Haemoglobin‬ ‭synthesis‬ ‭involves‬ ‭three‬ ‭key‬ ‭components:‬‭haem‬‭synthesis,‬‭globin‬‭synthesis,‬‭and‬‭the‬ H ‭availability of iron.‬ ‭Factors‬ ‭Required‬ ‭for‬ ‭Red‬ ‭Cell‬ ‭Production:‬‭Erythropoietin‬‭,‬‭produced‬‭by‬‭the‬‭kidney‬‭in‬‭response‬‭to‬‭oxygen‬‭levels,‬‭stimulates‬ ‭red‬‭blood‬‭cell‬‭production‬‭AND‬‭Vitamin‬‭B12‬‭(cobalamin)‬‭and‬‭folic‬‭acid‬‭(folate)‬‭are‬‭essential‬‭for‬‭DNA‬‭synthesis‬‭and‬‭are‬‭critical‬ ‭for erythropoiesis.‬ ‭Megaloblastic‬ ‭Anaemia‬ ‭and‬ ‭Vitamin‬ ‭B12‬ ‭Deficiency:‬ ‭megaloblastic‬ ‭anaemia‬ ‭(pernicious‬‭anaemia),‬‭characterized‬‭by‬‭larger‬ ‭red‬ ‭blood‬ ‭cells‬ ‭(megaloblasts),‬ ‭can‬ ‭result‬ ‭from‬ ‭vitamin‬ ‭B12‬‭deficiency.‬‭Vitamin‬‭B12‬‭deficiency‬‭leads‬‭to‬‭the‬‭inability‬‭to‬‭trap‬ ‭folate within red blood cells, disrupting DNA synthesis and causing‬‭larger‬‭, inefficiently maturing cells.‬ ‭Mechanism‬ ‭of‬ ‭Megaloblastic‬ ‭Anaemia:‬ ‭Vitamin‬ ‭B12‬ ‭deficiency‬ ‭prevents‬ ‭the‬ ‭trapping‬ ‭of‬ ‭folate‬ ‭within‬ ‭red‬ ‭blood‬ ‭cells,‬ ‭hindering‬‭the‬‭conversion‬‭of‬‭uridine‬‭to‬‭thymidine‬‭→‬‭RBCs‬‭attempt‬‭to‬‭insert‬‭uridine‬‭into‬‭DNA,‬‭disrupting‬‭synthesis‬‭and‬‭leading‬ ‭to‬ ‭the‬ ‭production‬ ‭of‬ ‭larger‬ ‭megaloblastic‬ ‭cells‬ ‭(additional‬ ‭cycles‬ ‭to‬‭attempt‬‭to‬‭correct‬‭errors)‬‭→‬‭RBCS‬‭(now‬‭megaloblastic‬ ‭cells)‬ ‭undergo‬ ‭apoptosis‬ ‭within‬ ‭the‬ ‭bone‬ ‭marrow,‬ ‭resulting‬ ‭in‬ ‭megaloblastic‬ ‭anemia‬ ‭and‬ ‭an‬ ‭elevation‬ ‭in‬ ‭bilirubin‬ ‭due‬ ‭to‬ ‭increased RBC breakdown.‬ ‭Neutrophils:‬ ‭Vitamin‬ ‭B12‬ ‭deficiency‬ ‭can‬ ‭also‬ ‭affect‬ ‭neutrophils,‬ ‭leading‬ ‭to‬ ‭hypersegmentation‬ ‭(additional lobes) in their nuclei‬ E‭ rythropoietin‬ ‭EPO‬ ‭-‬ ‭growth‬ ‭factor‬ ‭for‬ ‭erythroid‬ ‭development.‬ ‭It‬ ‭has‬ ‭been‬ ‭abused‬‭by‬‭athletes‬‭as‬‭it‬ ‭increases‬ ‭red‬ ‭cell‬ ‭mass‬ ‭and‬ ‭capacity‬ ‭for‬ ‭RBC‬ ‭to‬ ‭carry‬ ‭O2.‬ ‭It‬ ‭is‬ ‭produced‬ ‭mainly‬ ‭in‬ ‭the‬ ‭kidney‬ ‭by‬ ‭peritubular‬‭cells.‬‭Haem-containing‬‭protein‬‭senses‬‭oxygen‬‭need‬‭→‬‭synthesis‬‭of‬‭EPO.‬‭Interaction‬‭of‬‭EPO‬ ‭with receptor-bearing cells → increased red cell production.‬ ‭ ormal Shape of Red Blood Cells:‬ N ‭Appropriately‬‭assembled‬‭membrane‬‭proteins‬‭with‬‭the‬‭cytoplasmic‬‭cytoskeleton‬‭give‬‭red‬‭blood‬‭cells‬‭a‬‭biconcave‬‭disk‬‭shape.‬ ‭This‬ ‭biconcave‬ ‭disk‬ ‭shape‬ ‭allows‬ ‭for‬ ‭a‬ ‭high‬ ‭surface‬ ‭area-to-volume‬ ‭ratio,‬ ‭optimizing‬ ‭the‬ ‭oxygen-carrying‬ ‭capacity‬ ‭of‬ ‭haemoglobin.‬‭Transmembrane‬‭complexes‬‭embedded‬‭in‬‭the‬‭lipid‬‭bilayer‬‭contribute‬‭to‬‭the‬‭flexibility‬‭of‬‭red‬‭blood‬‭cells,‬‭which‬ ‭is‬‭essential‬‭for‬‭their‬‭ability‬‭to‬‭navigate‬‭through‬‭narrow‬‭capillaries‬‭and‬‭pass‬‭through‬‭the‬‭spleen‬‭.‬‭This‬‭flexibility‬‭decreases‬‭with‬ ‭the aging of red blood cells. Clinically relevant blood group antigens are present on these transmembrane complexes.‬ ‭Red‬ ‭Cell‬ ‭Shapes:‬ ‭The‬ ‭majority‬ ‭of‬ ‭red‬ ‭blood‬ ‭cells‬ ‭are‬ ‭disciform‬‭,‬ ‭meaning‬ ‭they‬ ‭are‬ ‭disc-shaped.‬ ‭However,‬ ‭a‬ ‭minority‬ ‭may‬ ‭exhibit‬‭a‬‭bowl-shaped‬‭morphology.‬‭The‬‭average‬‭diameter‬‭of‬‭red‬‭blood‬‭cells‬‭is‬‭in‬‭the‬‭range‬‭of‬‭7.2‬‭to‬‭7.9‬‭microns.‬‭Red‬‭blood‬ ‭cells have a‬‭centra