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28 Cards in this Set
- Front
- Back
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types of leukocytes |
-granulocytes -agranulocytes |
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granulocytes |
-aka myeloid cells -contain an irregular-shaped, lobed nucleus and permanent cytoplasmic granules -classified according to the staining properties of their granules -inflammatory cells -aid in direction of adaptive immunity -types: PMNs; eosinophils; basophils |
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agranulocytes |
-cytoplasmic granulation may often be seen, but is not a permanent feature of this cell class -types: lymphocytes; monocytes; macrophages |
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neutrophils |
-55-70% of the total circulating WBC pool -contain 3 types of cytoplasmic granules: primary or azurophilic; secondary/specific/definitive; teritary -phagocytose bacteria -chief cell of acute inflammation -migrate from blood in response to signals; transendotheilial migration involves complex interactions -short lifespan (6-8hrs in circulation) -engage in a single phagocytosis --> materials in vacuoles cannot be neutralized and degraded unless these agents are first killed -neutrophils are cleared by macrophages -dead PMNs make pus |
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primary or azurophilic granules |
-component of PMNs -lysosomal granules that contain antimicrobial compounds including myeloperoxidase -account for 1/3 of the granulae -following phagocytosis they fuse with endoosome or phagosome to kill and digest |
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secondary/specific/definitve granules |
-component of PMNs -non-lysosomal granules that do not stain basic or acidically -contains NADPH-oxidase subunits and MMPs -some fuse, but most appear to secrete their contents into the extracellular space |
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tertiary granules |
-component of PMNs -contain gelatinase (MMP-9) |
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eosinophils |
-2-5% of total circulating leukocytes -conspicuous acidophilic granules -degrade parasites (this MPO and cationic proteins seem to be effective in lysis of parasites -modulate inflammatory response (this role is not clear or well-established; they are recruited to sites of allergic reaction, but no direct evidence that they regulate) |
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basophils |
-least numerous circulating leukocytes -tissue resident counterpart is mast cell -involved in hypersensitivity reaction -basophilic granules contain: heparin, histamine -express receptors for IgE antibodies -following initial exposure to an antigen and antibody production, reexposure triggers binding the antigen to IgE-IgE receptor complexes and release of granules |
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lymphocytes |
-20-35% of circulating leukocytes -cooperate to form the basis of adaptive immune response -two classes: T and B cells |
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B cells |
-responsible for humoral immunity, the cellular basis of which is the maturation of a B cell into a plasma cell in response to a specific antigen -then produces and secretes an antibody Ig |
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T cells |
-basis of cell-mediated immunity |
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monocytes |
-3-8% of the circulating leukocytes -two distinct subsets; called in waves -first wave: inflammatory monocyte CD14+ (clear damage in pro-inflammatory phase) -second wave: CD16+ heal the wound and resolve inflammation -once in the tissue the monocytes differentiate into macrophages |
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macrophages |
-longer lifetime than neutrophils -probably engage in several phagocytotic events -tissue macrophages include: sinus-lining cells of: lymph sinuses, splenic sinuses, marrow sinuses, levnous sinuses of the liver; histocytes; microglia of CNS; alveolar macrophages; foreign body giant cells; epidermal langerhans cells |
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functions of macrophages |
-phagocytosis -scavengers: rid the body of worn-out cells and debris; important in development -antigen presenting cells: crucial in initiation and direction of adaptive immunity -secretory cells: produce enzymes, complement proteins, and regulatory factors such as interleukin-1 that regulate other cells at the site of injury or infection |
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consequences of respiratory burst |
-increased O2 consumption -production of superoxide -production of H2O2 and other ROS |
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respiratory burst |
-membrane bound components = flavocytochrome b -the other 3 subunits are cytosolic until it's activated -assembles into NADPH oxidase, which created superoxide |
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NADPH oxidase |
produces superoxide -mutation in this enzyme inhibits the production of reactive oxidants |
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superoxide dismutase |
produces H2O2 |
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myeloperoxidase |
breaks down H2O2 to hypochloric acid |
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leukocyte migration |
-controlled movement of leukocyte through the body -regulates immune response by promoting proper cell positioning and cell-cell interactions -also called trafficking, extravasation, diapedesis, recruitment, and homing -takes place in post capillary venules |
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control of inflammation |
-cell adhesion molecules and chemokines expressed by endothelial cells and leukocytes that regulate migration into and out of tissues -four families of CAMs: mucin-like CAM and integrins on leukocytes, selectins and Ig-superfamily CAMs on endothelial cells -selectins <--> mucin-like CAMs -integrins <--> Ig-superfamily CAMs -chemokines are small molecule chemoattractants that interact with G-protein coupled receptors |
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mechanisms of trafficking |
-patterns and mechanisms are similar -best characterized example is neutrophil trafficking in response to injury |
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multi-step model of leukocyte trafficking |
-resident macrophage recognize invader (pattern recognition) -secrete cytokines that activate endothelial cells -selectin vesicles in endothelial cells fuse and tether leukocytes causing them to roll (tethering and rolling) -inflammatory cytokines also initiate transcription of other adhesion molecules (arrest and adhesion) -transendothelial migration -steps are overlapping and combinatorial -specificity and diversity in migration is due to diversity in adhesion molecules and chemokines |
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tethering and rolling |
-selectin-mediated adhesion is very weak interactions so it's catch and release --> allow rolling |
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activation, arrest, and adhesion |
-chemokines are presented by endothelium and interact with their receptor (outside in signaling) -selectin enables chemokine receptors on the neutrophil to come into contact with chemokines -integrins on neutrophils are then activated (inside out signaling) -integrins bond with IgSF-CAM --> even more interactions with endothelium |
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transendothelial migration |
-takes ~90 seconds -leukocyte extends across endothelial junctions (adhestion molecule zipper) -some exit through the cells -vascular integrity is maintained |
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perivascular regulation of neutrophil egress |
-basement membrane: protective meshwork -perivascular macrophages and mast cells: elicit chemokines to sustain neutrophil attraction -pericytes: embedded in basement membrane -once through endothelium, PMNs migrate to gaps between pericytes (integrin dependent) -preferential sites |
