AHT 1210 Module B Review PDF

AHT 1210 Module B Review Leukopoiesis: WBC production White Blood Cell Area Produced -​ Stimulus for production = Leukopoietin...

AHT 1210 Module B Review Leukopoiesis: WBC production White Blood Cell Area Produced -​ Stimulus for production = Leukopoietin Granulocytes Bone Marrow -​ WBC use the circulatory system to transport from the site of production to the final (Neutrophils, Basophils, destination which are the tissues Eosinophils) Monocytes Bone Marrow Circulating Pool (CP): freely circulating in the blood, these cells are collected when taking Lymphocytes Bone Marrow or Thymus a blood sample. -​ Comprises about 50% of total WBC in blood vessels Marginated Pool (MP): stuck or are rolling along the inside walls of the blood vessel -​ Animal with the largest MP is the cat = 75% Granulopoiesis - production of granulocytes -​ Cells get smaller as they mature -​ The nucleus change as the cells mature by becoming more condensed, then bean shaped and finally segmented -​ The cytoplasm changes from a deep blue color in the blast, to clear with distinctive granules in the mature granulocyte Mitotic Pool -​ Contains cells capable of undergoing mitosis -​ Myeloblasts, promyelocytes and myelocytes Maturing pool -​ Contains cells that are immature but which can no longer undergo mitosis -​ Metamyelocytes and band cells ​ Storage or -​ Contains mature granulocytes waiting to be Reserve Pool released into the blood  Cell Size Nucleus Cytoplasm Myeloblast 14-20 um diameter Large, round, lacy and red-purple in Small in volume relative to the nucleus, a deep blue in color color and no inclusions (granules) Promyelocyte Decreasing in size Still large and round, dark red-purple Usually lighter blue than in the blast, some medium in color sized nonspecific granules now appear Myelocyte Decreasing in size Smaller, round, more condensed and Now a light blue color or clear, the appearance of no dark purple specific types of granules gives rise to three different myelocytes - neutrophil, eosinophil and basophil Metamyelocytes Decreasing in size Now indented or kidney bean shaped, Clear or light pink with increased specific and very condensed, dark purple or black decreased non specific granules in color Bands Similar in size as mature Smaller and band shaped, dark Clear or light pink in color with increased specific granulocytes purple to black in color granules Polymorphonuclear 10-15 um diameter Egmenting into lobes, dark purple to Neutrophil: clear or faint pink in color with specific Granulocytes black granules Eosinophil: orange-red granules Basophil: dark purple or black granules Productions of Monocytes -​ Monocytes are agranulocytes -​ Monocytes are produced in the bone marrow and are immediately released into the circulation -​ Monocytes circulate in the blood for 1-2 days, then enter the tissues and become macrophages 1.​ Free Macrophages: found in body cavities, in the alveoli and at sites of inflammation - move from one tissue to another 2.​ Fixed Macrophages: reside in a specific tissue type and are not motile. Tissues that contain fixed macrophages include the liver, the spleen, bone marrow, lymph nodes and gastrointestinal tract  Cell Size Nucleus Cytoplasm Monoblast 14-20 um diameter Large, round, red purple in color Deep blue in color Promonocyte Similar to a monocyte Beginning to indent Light blue with a few small azurophilic granules Monocyte 16-20 um diameter Large with variable shape from round Large volume, light gray to blue gray to elongated to twisted, but is usually in color, small vacuoles twisted or folded in some way - stringy or web like Production of Lymphocytes -​ Lymphocytes are agranulocytes -​ Lymph nodes and other lymphoid tissue are where some lymphocytes mature -​ B lymphocytes: lymphoid tissue acquires its population of cells in the fetal and young animal from lymphoblast proliferation in the bone marrow and most of these travel via the blood to the lymphoid tissue and these become B lymphocytes and natural killer cells -​ T Lymphocytes: lymphocytes that are produced in the bone marrow travel to the thymus before travelling to the lymphoid tissue -​ Lymphocytes can move back and forth between the tissues, the blood and lymphoid tissue Module B2 Function of Leukocytes Neutrophil Functions: most numerous leukocyte in the blood and bone marrow -​ Very short life span of 3-5 days in production and 10 hours in the blood and a few days in the tissues -​ Locate and phagocytose pathogenic microorganisms -​ First cells to arrive at the site of infection and ultimately die after phagocytosis -​ One way movement from the blood to the tissues -​ Neutrophils migrate to the site of infection and then kill by phagocytosis Migration Sequence (Emigration) 1.​ Margination and Adherence -​ 50% of the neutrophil population in the blood vessels is lying in contact with the blood vessels  -​ Adherence to the blood vessel wall occurs at sites of inflammation in response to chemotaxins (chemicals which are released during inflammation and cause specific cells to move towards them) 2.​ Diapedesis -​ In response to a chemotactic agent, the neutrophil squeezes between the endothelial cells of the blood vessel walls and enters the tissues 3.​ Migration -​ Following the concentration of the chemotaxis, the neutrophil will move through the tissue to the area of infection Phagocytosis (The Killing Cascade) 1.​ Immune Adherence -​ The neutrophil recognizes the microbe (antigen) by binding to its cell surface -​ This process is enhanced by opsonization 2.​ Endocytosis -​ The microbe is engulfed by the neutrophil and becomes a phagosome 3.​ Lysosome Fusion -​ The neutrophil granules are lysosomes, which attach to the walls of the phagosome and discharge their contents into the vacuole 4.​ Killing and Digestion -​ The potent killing enzymes released into the phagosome from the lysosomes kill the microbe, the hydrolytic enzymes break down the remains of the microbe -​ Useful components from the microbe are absorbed into the cytoplasm and are used by the neutrophil 5.​ Exocytosis -​ Waste products in the phagosome are eliminated from the cell by exocytosis -​ Neutrophils will continue killing microbes until they run out of granules, then they die -​ Dead, neutrophils form pus, they are lysed and their remaining contents contribute to the inflammatory response Monocyte/Macrophage Functions: -​ Circulate in the blood for 25-36 hours before moving into the tissues -​ Monocytes move into the tissues in a random fashion or in response to a chemotactic stimulus -​ Once in the tissues they rapidly transform into macrophages , growing larger to accommodate the increased number of organelles and lysosomes accumulating in the cytoplasm  -​ Macrophage Functions: -​ Catabolism of RBC and iron metabolism -​ Catabolism of other dead tissue cells -​ Removal of toxins, activated coagulation factors and immune complexes from the blood 1.​ Phagocytosis 2.​ Producing monokines 3.​ Antigen presenting cells (APC) Phagocytosis -​ Neutrophils provide the first and rapid response to infection, while macrophages provide prolonged response and also clean up dead neutrophils -​ Macrophages = chronic infections, survive much longer than neutrophils Monokines -​ Macrophages can become activated by lymphokines secreted by helper T cells -​ Once activated, macrophages become bigger, more mobile and increase their rate of phagocytosis -​ They will secrete monokines which enhance other cells in the immune process and act as pyrogens (produces fever) in the inflammatory response Antigen Presenting Cells (APC) -​ Some macrophages act a antigen presenting cells -​ These cells are essential for the activation of cell mediated immunity (memory cells) in the specific immune response -​ An APC phagocytosis the foreign antigen, processes it, and then displays it on its cell surface Lymphocyte Functions 1.​ Cell mediated immunity (CMI) -​ Mediated by T lymphocytes -​ It always involves cells attacking cells and is directed against intracellular pathogens and cells such as cancer cells and foreign tissue transplants 2.​ Humoral or Antibody Mediated Immunity (AMI)  -​ Mediated B lymphocytes -​ Involves the production of antibody (Ab) in response to Ag in body fluids and extracellular pathogens Cell Mediated Immunity -​ Each T cell has its own unique Ag receptor on its cell surface -​ T cells can only bind to a FAg and become activated if the FAg is presented on the surface of the APC -​ APCs are macrophages that ingest the foreign cell, process the FAg and then present it on their cell surface -​ Once the T cell binds with its specific FAg on the APC surface, the T cell becomes activated -​ The activated T cell begins dividing rapidly and the resulting differentiate into 4 types Helper T cells Produce chemical mediators called lymphokines, which “help” other parts of the immune response Killer T cells Once bound to the antigen, the killer T cell kills the FAg cell by punching holes in its cell membrane or by producing a toxin that disrupts its DNA They can then detach and attack other cells Suppressor T cells Regulate the immune response by producing lymphokines that inhibit T cell proliferation, reduce helper and killer T cell functioning and prevent B cells from transforming to plasma cells Memory T cells After the immune response has subsided, thousands of memory T cells remain The cells will recognize the FAg that originally stimulated their production and they will initiate a larger, swifter response if the FAg appears again Natural Killer Cells (NK Cells) -​ Cells kill target cells which are not sensitized by antibody or complement -​ The NK cell kills its target cell by binding to it, then discharging its granules onto the target cell membrane -​ The granules punch large holes in the cell membrane of the target cell causing it to explode -​ After the NK cell has killed its target cell it detaches, forms new granules, and cruises off, searching for another “victim” Antibody Mediated Immunity (B Cells) -​ B cells reside in the lymphoid tissue -​ When a B cell encounter a FAg that matches its specific antigen receptor, it binds to the FAg and becomes activated -​ An activated B cells begins dividing, resulting in two populations of cells: memory B cells and plasma cells -​ Each memory B cell carries the same specific antigen receptor as the activated B cell, these cells reside in lymphoid tissue and live for years, providing long term immunity against reinfection -​ When exposed to the same FAg that triggered their creation, memory B cells initiate a very rapid secondary immune response -​ The plasma cells become metabolically activated and begin producing antibody, which is released into the bloodstream Antibody Function IgG Most abundant in blood plasma, found in lymph and the intestine Small: the only Ig that can cross the placenta Most antibodies to bacteria, virus, parasites and fungi are IgG Enhance phagocytosis, neutralizes toxins, activates complement IgA Major Ig in external body secretions: sweat, tears, saliva, mucus and colostrum IgE Located on mast cells, basophils and eosinophils Involved in allergic and hypersensitivity reactions and protection against parasites IgM Largest Ig, found almost exclusively in the blood IgD Found in minute amounts in blood and lymph Increased in chronic diseases Eosinophil Function -​ When the eosinophils arrive at the site of the activated mast cell, they suppress the hypersensitivity reaction by de-granulating and releasing: -​ Prostaglandin: prevents further mast cell degranulation  -​ Antihistamine: which deactivates histamine -​ SRSA deactivator: turns of SRSA and in addition the eosinophils phagocytose the opsonized allergen and mast cell granules Basophil/Mast Cells Function -​ Present in small numbers in the peripheral blood and in large numbers in the tissue where they survive for several weeks -​ Mast cells are found in tissues and rarely in blood -​ Mast cell granules contain: -​ Heparin -​ Histamine -​ Eosinophilic Chemotactic factor (ECF) -​ Surface membranes of the mast cells contain many IgE receptors Immunity to Parasites -​ The presence of a parasite results in the production of IgE by plasma cells WBC Description -​ The IgE sensitizes the mast cells and sticks to the parasite Morphology -​ Allergens produced by the parasite bind to the sensitized mast cell Penia Decreased numbers of cells in the causing degranulation. Which causes an immediaete hypersensitivity blood. Neutropenia indicates a reaction and attacks eosinophils to the site decreased number of neutrophils in the blood -​ Eosinophils will bind to the opsonized parasite -​ The parasite is too big to phagocytose, but the eosinophils can kill it by Philia or Increased numbers of cells in the blood de-granulating onto the integument of the parasite Cytosis Neutrophilia indicates increased neutrophil numbers -​ The cytotoxic components of the granules damage the integument and Monocytosis indicates increased the parasite subsequently dies monocyte numbers Leukemia Neoplastic cells are present in the blood Module B3 Quantitative Changes of Leukocytes Leukocyte Tests and Numbers Leukemoid Marked leukocytosis usually caused by Response inflammatory disease -​ Total WBC Count: the number of leukocytes per liter of blood in a blood specimen -​ WBC Differential Count: reflects the relative populations of WBC types in the sample and the absolute number of teh WBC types in the sample Module B4 Leukocyte Abnormalities Causes of Neutrophilia - high neutrophil count Four main types of neutrophilia: 1.​ Physiologic 2.​ Glucocorticoid associated 3.​ Acute inflammatory 4.​ Chronic inflammatory - The first two type occur in normal, healthy animals and 3 and 4 due to disease Physiologic Neutrophilia Occurs as the result of epi and norepi release associated with fear, excitement or exercise Causes neutrophils to move from the marginated pool to the circulating pool Seen in most healthy animals and especially in cats due to their larger MP Neutrophil count returns to normal in about 1 hour after the stimulus ends Glucocorticoid Neutrophilia Caused by the effects of endogenous or exogenous glucocorticoids (physical or neurogenic stress)​ (Stress) Fever neutrophils in the MP and more in the CP Fewer neutrophils enter the tissue so they have increased CP Increased release of segs from the storage pool This can result in neutrophil counts that are double the normal count Acute Inflammatory An inflammatory reaction, which can cause increased tissue demand Neutrophilia This will result in an increased release of segmented and band neutrophils Infectious (bacterial, viral, fungal, protozoan) Chronic inflammatory The duration of the inflammatory process (at least a week) and indicates that granulocytic hyperplasia has occurred Neutrophilia Neutrophilia occurs because the release of neutrophils from the marrow exceeds the migration of neutrophils into the tissues Causes of NeutroPENIA - low neutrophil count Two main types: 1.​ Inflammatory/Active Tissue Demand 2.​ Decreased production - Both are due to disease (no physiologic neutropenia)  Inflammatory Neutropenia due to Occurs with severe acute inflammatory disease Overwhelming Tissue Demand Results with margination and emigration of neutrophils into inflamed tissue exceeds the release from the bone marrow Neutrophil production is also stimulated, but the results take at least two days to occur Causes: bacterial infections, endotoxins, viral infections, inflammatory states in cattle Inflammatory neutropenia is common in cattle because they have a smaller storage pool Decreased or Ineffective Decreased production due to destruction of stem or blast cells in the bone marrow Production Neutropenia Ineffective production occurs when neutrophil precursors are damaged and die before they can be released Cause can be infectious, neoplastic, toxic or myelofibrotic Causes of Lymphocytosis - increased lymphocytes Four types: 1.​ Lymphocytosis of young animals - occur normal​ 2.​ Physiologic - occur normal 3.​ Chronic inflammatory - due to disease 4.​ Neoplastic - due to disease Lymphocytosis of young animals Puppies, kittens, calves and foals have higher lymphocyte counts Physiologic Lymphocytosis Due to the effects of catecholamines causing lymphocytes to move from the MP to CP Can last minutes to hours Can result in a doubling of lymphocyte count See most frequently in cats and young horses Chronic inflammatory Lymphocytosis Results from increased lymphopoiesis in response to chronic antigenic or cytokine stimulate (bacterial infections, systemic fungal infections, FeLV, EIA, BLV) The lymphocytosis is part of a hyperplastic lymphoid system which can result in enlarged lymph nodes Lymphocyte count is usually 2-3 times that of norma and may be reactive Neoplastic Lymphocytosis Due to the neoplastic proliferation of lymphoid cells in the lymph nodes. BM and tissues Extreme lymphocytosis occurs with many lymphocytes having abnormal, immature morphology Causes of LymphoPENIA - decreased lymphocytes 1.​ Glucocorticoid associated 2.​ Acute inflammatory 3.​ Lymphosarcoma  Glucocorticoid Associated Due to endogenous or exogenous glucocorticoids (physiologic or neurologic stress) Movement of lymphocytes from CP to the tissues and lymph nodes Chronically elevated glucocorticoid levels cause lymphoid hypoplasia and decreased production Acute Inflammatory Due to changes in lymphocyte kinetics stimulated by inflammatory mediators Lymphopenia The CP is reduced as lymphocytes move into inflamed tissue and lymph nodes Fewer lymphocytes leave the lymph nodes Most acute inflammatory leukogram have a lymphopenia Lymphosarcoma Characteristics Clinical Signs Diagnosis Treatment 70% cats with lymphoma Multicentric: generalized large LN, FNA Decision to treat test positive for FeLV non painful, most common Mediastinal: enlarged mediastinal LN, Biopsy Chemotherapy protocols dyspnea, decreased heart sounds, non compressible cranial thorax Bone marrow biopsy Non surgical disease Alimentary: may have palpable mass, thickened intestines, anorexia, weight CBC/Chem/UA loss, v and d -​ Hyperkalemia Extranodal: disease affecting tissues and organs, irregular kidneys, PU/PD, Radiographs - thoracic cutaneous, neural and abdominal Abnormal Monocyte Concentrations - Monocytosis 1.​ Glucocorticoid associated (Stress): due to glucocorticoid hormone sor drugs which cause a shift from the MP to the CP -​ Common in dogs and cats -​ Rare in horses and cattle 2.​ Inflammatory Monocytosis: both acute and chronic inflammation produces cytokines, which stimulate monocyte production and release 3.​ MonocytoPENIA: difficult to document because healthy animals have few monocytes Abnormal Eosinophil and Basophil Concentrations Eosinophilia - increased Usually related to eosinophil anti inflammatory function after mast cells degranulation, allergic reactions or allergies eosinophils Mild eosinophilia occasionally seen in normal animals Parasitized animals but not all will have eosinophilia Hypersensitivity Parasitism Idiopathic Flea allergy dermatitis, milk allergy in Ectoparasites, heartworm and tissue Eosinophilic myositis in dogs or ruminants, asthma nematodes, trematodes or protozoa eosinophilic granuloma complex in cats EosinoPENIA Eosinophil numbers in healthy animals are low, documenting is difficult - little diagnostic significance BasoPHILIA Only considered to be diagnostic if significant or persistent Allergic Reactions Parasitism Neoplasia Drugs, food, inhalants, insect bites or Fleas, gastrointestinal nematodes, Basophilic leukemia, mast cell neoplasia, stings heartworm feline myeloproliferative disease, polycythemia vera BasoPENIA Cannot be documented because normal low basophil count Mastocytemia When mast cells occur in the peripheral blood Finding even one mast cell indicates mastocytemia Canine cutaneous Mast Cell Neoplasia Leukogram Patterns Parameters to determine leukograms: 1.​ Total WBC count 2.​ Number of neutrophils 3.​ Age of neutrophils (bands, segs, hyper segmented) 4.​ Number of lymphocytes 5.​ Whether a monocytosis is present or not Left Shift An increased concentration of non segmented neutrophils (BANDS) When tissue demands are high and the storage pool is depleted so cells are released from the maturing pool Is considered to be hallmark of acute inflammation but mild left shifts can occur with glucocorticoid hormones and endotoxins Regenerative Left Characterized by a leukocytosis due to neutrophilia with the appearance of immature neutrophils Shift Indicated that the neutrophil response to the inflammatory event is appropriate as production and release are responding to the demand Degenerative Left Immature neutrophils exceeds the number of mature neutrophils and the leukocyte count is low or normal Shift Indicates that neutrophil production and release cannot meet the tissue demand If a degenerative left shift is persistent then there is inadequate neutrophil production and the animals condition is deteriorating Right Shift An increased concentration of hyper segmented neutrophils (5 or more) Hyper segmentation indicates older cells Most common in stress leukogram Species Specific Leukocyte Responses Dogs Most pronounced acute inflammatory leukocytosis Stress leukogram is most common Cats The most prone to physiological leukocytosis FeLV infection can cause a variety of alterations in cell numbers and morphology Cattle Inflammatory conditions such as mastitis and pneumonia result in neutropenia because cattle have a small neutrophil storage pool Inflammation can cause morphological changes in lymphocytes that are difficult to differentiate from neoplastic changes Horses Frequently have little or no neutrophilia or left shift during inflammatory states A pronounced left shift is rare unless toxic changes are present