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25 Cards in this Set
- Front
- Back
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What percentage of WBCs are neutrophils and what is their function?
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Neutrophils constitute 40 to 70% of total WBCs; they are a first line of defense against infection
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How long is the half life of neutrophils?
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Mature neutrophils have a half-life of about 2 to3 days.
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What causes neutrophils to leave the circulation?
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During acute inflammatory responses (eg, to infection), neutrophils, drawn by chemotactic factors and alerted by the expression of adhesion molecules on blood vessel endothelium, leave the circulation and enter tissues.
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How do neutrophils interact with pathogens?
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Their purpose is to phagocytose and digest pathogens.
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How specifically do neutrophils kill pathogens?
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Microorganisms are killed when phagocytosis generates lytic enzymes and reactive O2 compounds (eg, superoxide, hypochlorous acid) and triggers release of granule contents (eg, defensins, proteases, bactericidal permeability-increasing protein, lactoferrin, and lysozymes). DNA and histones are also released, and they, with granule contents such as elastase, generate fibers in the surrounding tissues; the fibers may facilitate killing by trapping bacteria and focusing enzyme activity.
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What percentage of WBCs are eosinophils and what are their targets?
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Eosinophils constitute up to 5% of WBCs. They target organisms too large to be engulfed;
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How do eosinophils kill parasites?
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They kill by secreting toxic substances (eg, reactive O2 compounds similar to those produced in neutrophils), major basic protein (which is toxic to parasites), eosinophil cationic protein, and several enzymes. Eosinophils are also a major source of inflammatory mediators (eg, prostaglandins, leukotrienes, platelet-activating factor, many cytokines).
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What percentage of WBCs are Basophils and with what other (unrelated) cell type do they share characteristics?
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Basophils constitute < 5% of WBCs and share several characteristics with mast cells.
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How are Basophils and Mast cells functionally related?
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Both have high-affinity receptors for IgE called FcεRI. When these cells encounter certain Ags, the bivalent IgE molecules bound to the receptors become cross-linked, triggering cell degranulation with release of preformed inflammatory mediators (eg, histamine, platelet-activating factor) and generation of newly synthesized mediators (eg, leukotrienes, prostaglandins, thromboxanes).
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Cytotoxic leukocytes include
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Natural killer cells
Lymphokine-activated killers |
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NK cells are what type of WBC? They make up what percentage of that type of WBC in the peripheral blood?
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Natural killer (NK) cells: Typical NK cells constitute 5 to 15% of peripheral blood mononuclear cells
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Characterize the shape of their nucleus and morphology of their cyto plasm.
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They have a round nucleus and granular cytoplasm.
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What function do NK cells perform?
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NK cells induce apoptosis in infected or abnormal cells by a number of pathways
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What is thought to be a major purpose of NK cells?
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Typical NK cells are thought to be important for tumor surveillance.
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NK cells can only kill when target cells lack _____.
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NK cells can kill their target only when there is no strong signal from inhibitory receptors. MHC class I molecules (normally expressed on nucleated cells) therefore prevent destruction of cells; their absence indicates that the cell is infected with certain viruses that inhibit MHC expression or has lost MHC expression because cancer has changed the cell
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What areLymphokine-activated killers (LAK)?
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Some leukocytes develop into potent lymphokine-activated killers, capable of killing a wide spectrum of tumor target cells and abnormal lymphocytes (eg, infected with certain viruses). These cells are a phenomenon rather than a unique subset of cells. LAK precursors are heterogeneous but can be classified primarily as NK-like (most common) or T-cell–like.
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The 2 main types of lymphocytes are...
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B cells (which mature in bone marrow)
T cells (which mature in the thymus) |
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How are B and T cells distinguished from each other?
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They are morphologically indistinguishable but have different immune functions. They can be distinguished by Ag-specific surface receptors and molecules called clusters of differentiation (CDs), whose presence and absence define some subsets. More than 300 CDs have been identified (for further information on CD Ags, see the Human Cell Differentiation Molecules web site at www.hlda8.org/). Each lymphocyte recognizes a specific Ag via surface receptors
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What percentage of the WBCs are B cells and where can they be found?
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About 5 to 15% of lymphocytes in the blood are B cells; they are also present in the spleen, lymph nodes, and mucosa-associated lymphoid tissues.
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What is the primary function of B cells?
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B cells can present Ag to T cells, but their primary function is to develop into plasma cells, which manufacture and secrete antibodies
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What part does Ag recognition play in the function of B cells?
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B cells have the potential to recognize an almost limitless number of unique Ags.
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In what 2 ways do B cells respond to antigen?
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Primary immune response and Secondary (anamnestic or booster) immune response
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What is the primary immune response of B cells?
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Primary immune response: When mature naive B cells first encounter Ag, they become lymphoblasts, undergo clonal proliferation, and differentiate into memory cells, which can respond to the same Ag in the future, or into mature Ab-secreting plasma cells. This response is characterized by a latent period of days before Ab is produced. Initially, only IgM is produced. With the help of T cells, B cells can further rearrange their Ig genes and switch to production of IgG, IgA, or IgE. Thus, on first exposure, the response is slow and provides limited protective immunity.
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What is the secondary immune response of B cells?
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Secondary (anamnestic or booster) immune response: When memory B and TH cells are reexposed to the Ag, the memory B-cells rapidly proliferate, differentiate into mature plasma cells, and promptly produce and release large amounts of Ab (chiefly IgG because of a T cell–induced isotype switch) into the blood and other tissues, where Ab can react with Ag. Thus, after reexposure, the immune response is faster and more effective.
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What are the 3 main types of T cells?
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. There are 3 main types of T cell:
Helper Regulatory Cytotoxic |
