White Blood Cells And Platelets PDF

Dr./ Rasha Mohammed Ali Physical Therapy Lecturer of Medical Physiology, Faculty of Medicine, Assiut University First year...

Dr./ Rasha Mohammed Ali Physical Therapy Lecturer of Medical Physiology, Faculty of Medicine, Assiut University First year 1 Objectives: 1- To define immunity and determine its mechanisms 2- To identify different types of granulocytes and their functions. 3- To describe types and functions of lymphocytes 4- To list common WBCs disorders 5- To define immune tolerance and autoimmune diseases 6- To describe the function of the platelets (platelet plug formation) 7- To list types of platelets disorders Blood has four major elements: Red blood cells (Erythrocytes) RBC White blood cells (Leukocytes) WBC Platelets (Thrombocytes) Plasma 3  This is composed of the blood leukocytes (the white blood cells) and tissue cells originally derived from the leukocytes. These cells all work together in two different ways to prevent disease: (IMMUNITY) 1-by destroying invading agents by the process of phagocytosis and 2-by forming antibodies and sensitized lymphocytes, one or both of which may destroy the invader. 5 WBCs Count 4000-11000/ µL 1 Liter = 1,000,000 µL 4,000,000,000 – 11,000,000,000 /L 4 – 11 × 9 10 /L 6 WBC TYPES Lymphocytes Eosinophils Basophils Neutrophils Monocytes 7  Nomenclatures/Differential count Neutrophils (has neutrophilic granules) 50–70% Eosinophils (has acidophilic granules) 1-4% Granulocytes Basophils (has basophilic granules) 0-2% Lymphocytes (has no granules) 20–40% Agranulocytes Monocytes (has no granules) 2–8% Neutrophils = polymorphonuclear leukocytes (PMN) (or polymorphs) because of their multilobed nucleus Lymphocytes = cells of lymphoid system Monocytes = has single large nucleus 8 WBCs - concerned with nonspecific immunity: 1- Monocytes 2- Neutrophils 3- Eosinophils 4- Basophils WBCs - concerned with specific immunity: Lymphocytes 9  Neutrophils Normally = (50 – 70%) 1.5 – 10 × 109 /L > 10 × 109/L = neutrophilia o Bacterial infection o Tissue necrosis (e.g. Myocardial infarction) < 1.5 × 109 /L = neutropenia or agranulocytosis 10  Their primary function is to 1. Ingest and destroy invading microorganisms in tissues. 2. Neutrophil can cause effective ‘Phagocytosis’ –to kill foreign particles and microbes. Form first line of defense. 3. They play a central role in the early stages of the acute inflammatory response to tissue injury. 4. Are the major constituent of pus. 11 Neutrophils migrate into areas of tissue damage where they have a defensive role 12 Neutrophils have a role in Phagocytosis of bacteria and dead cells 13  Neutrophil - Role in Inflammation / Phagocytosis Neutrophil blood cells are very important in combating acute inflammation in body by the process of ‘leukocytes adhesion cascade’ reaction i.e.: Margination, Rolling, Adhesion, Diapedesis Chemotaxis and Phagocytosis  Phagocytosis- : to eat cells It is Process of ingestion and destroying of foreign microbes/antigens. Endocytosis-Taking in Microbes and cell debris ↓ Formation of Phagosome ↓ lysosome Phagolysosome  KEY FACTS One of the myeloid series of white blood cells One of the granulocyte type of white blood cells Main role in phagocytosis and bacterial killing Increase in number in blood in bacterial infection and inflammation (‘neutrophilia’). Leukaemia: is a malignant neoplasm that involve HSC in the bone marrow and results in formation of high numbers of abnormal nonfunctional white blood cells. These white blood cells are not fully developed and are called blasts or leukemia cells. 17  a) They may absorb histamine released in allergic conditions. They may also detoxify toxins and foreign proteins which increase in these conditions. b) They are weak phagocytes. c) Protection against parasitic disease 18  Basophils are the least common WBCs. Large, intensely basophilic, cytoplasmic granules Functions: 1- Exposure to allergens results in rapid exocytosis of basophil granules, thereby releasing histamine resulting in an immediate hypersensitivity reaction. Such a reaction causes allergic rhinitis, urticaria and anaphylaxis. 2- They secrete heparin (= anticoagulant). 19  Basophils share a common lineage with tissue mast cells, with which they have many structural and functional similarities. Both cells have highly specific membrane receptors for the IgE produced in response to allergens 20  Monocytes Monocytes are large motile, phagocytic cells. Function of Monocytes (= macrophages): a) They are highly phagocytic. They leave blood to connective tissues (by diapedesis) where they change to macrophages engulfing bacteria. b) Tissue repair after inflammation. 21  A- The Innate – Nonspecific immune system o Barriers – epithelium, secretions , fluid flow o Cells: phagocytes (neutrophils, macrophages), o Chemical signals – interferons, complement proteins, Nonspecific (Innate) because each process works no matter what the invader is. The innate mechanisms were present prior to the development of lymphocytes and the Adaptive Processes ▪ B- The Acquired- adaptive immune system 1- Unlike the innate immune system, the adaptive immune system provides : ▪ Specific ▪ Delayed Powerful immune response 2- It Relies on B cells and T cells. 1- B cells ▪ After formation and maturation in the bone marrow (hence the name “B cell”), the naive B cells move into the lymphatic system to circulate throughout the body. ▪ B cells each have one of millions of surface antigen-specific receptors (membrane-bound antibodies). Plasma Cells Are formed from B lymphocytes and secrete immunoglobulin (antibodies): Humoural immunity When a naive B cell encounters an antigen that fits its membrane-bound antibody, it quickly divides in order to become either a memory B cell or an effector B cell, which is also called a plasma cell. 25 2- T cells Once formed in the bone marrow, T cells migrate to the thymus (hence the name “T cell”) to mature and become T cells. While in the thymus, the developing T cells start to express T cell receptors (TCRs). Mature T cells should recognize only foreign antigens presented by antigen presenting cells APCs (e.g. Macrophages) in order to mount an appropriate immune response: Cell Mediated immunity APCs T Cell  1- Helper T cells help with the activation of T and B cells, and other immune cells. Types of T 2- Cytotoxic T cells are responsible for removing lymphocytes pathogens and infected cells. 3- Regulatory T cells help distinguish between self and non- self molecules reducing the risk of autoimmune diseases. during fetal life Autoimmune diseases ▪ Key Facts: ▪ 1- B and T lymphocytes: (Specific Immunity) ▪ 2- B lymphocytes: ✓ They recognize antigens directly ✓ They produce antibodies: Humoral immunity ▪ 3- T lymphocytes ✓ They recognize antigens indirectly ( The antigen must be presented by APCs to the T cells) ✓ They form sensitized T lymphocytes (3 types): Cell Mediated Immunity Leukocytosis Neutrophilia: Bacterial inflammation Eosinophilia: allergic and parasitic diseases Basophilia: allergic disease Lymphocytosis: Viral, chronic bacterial inflammation leukopenia 1.Bone marrow depression 2.Splenomegaly 3.Autoimmune disorders  The spleen 1 2 3 4 Defense: Blood Removal of Old Blood against parasite Formation Blood Cells: Reservoir: and microbes  Platelets (Thrombocytes( Small cell fragments derived from megakaryocytes and are important in haemostasis BLOOD PLATELETS (Thrombocytes) These are granular non-nucleated oval bodies, about 2-4 micron in diameter. They have a short life span (8-12 days). The normal platelet count is 150-400× 109/L 34 Haemostatic role of platelets in health: how do they work? Platelets circulate in a resting, inactive state Must become activated Must stick together = Aggregation Platelet Activation Pathways COLLAGEN THROMBIN ADP GpIIb/IIIa GpIIb/IIIa GpIIb/IIIa Aggregation Adrenaline Platelet Adhesion vWF Endothelium Exposed Collagen  Functions of Platelets Phagocytosis: Platelets can Platelets store and Haemostasis: phagocytose particles as carbon and transport serotonin viruses. A- Marked constriction of the injured vessels due to release of a vasoconstrictor substance called “Serotonin” B- Platelets then adhere together and plug the vessel opening. C- Releasing factors which help blood coagulation  Abnormalities of Blood Platelets Thrombocytopenia 2- Thrombasthenia (Thrombocytopenic Purpura) It is a state in which the very low level of platelets i.e. platelets defective in below 50.000/cubic millimeter. function. a) Idiopathic thrombocytopenia: e.g. in severe uremia and which means: the cause is exposure to certain drugs as unknown. aspirin. b) Secondary thrombocytopenia: occurs in association with aplasia of the bone marrow e.g. exposure to X ray, radioactive substances, 39