MCDB 132 - HOST DEFENSES: First line: skin: nothing can...

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HOST DEFENSES: First line: skin: nothing can penetrate without a carrier, or through a wound ~ its dry ~ covered in microflora defense is based on competition here mucosal surfaces (4): 1) gastrointestinal 2) respiratory 3) urogenital 4) conjunctiva defense cells (phagocytes 5): 1) monocytes (live for weeks): circulate in blood and develop into macrophages 2) macrophages (live for weeks): antigen presenting cells (APCs) which circulate in the blood and are primarily fixed in immune tissues 3) PMNs (live < 1 day): most abundant, circulate in blood, 1 st phagocyte to infection 4) Cytotoxic T cells (CD8+): deliver toxic granules to host cells infected with specific pathogens 5) NK cells : deliver toxic granules to host cells infected by a variety of pathogens Second line: WBCs here are some tests done to ID if WBCs are active (responding to a pathogen): 1) total WBC count (total per microliter of blood) ~ normal = 4500-10,000 ~ severe infection = > 30,000 ~ risk to fatal infection = < 500 ~ also need to look for granulocytes : PMNs eosinophils: react to extracellular parasites basophils: make histamines and induce inflammation ~ in addition note agranulocytes : monocytes lymphocytes: B, T, and NK cells 2) CD4+/CD8+ ratio test: T cell markers are used to assess HIV progression ~ normal ratio = 2 ~ HIV infected ratio = 0.5 if 0.1 = really sick Third line: ~ complements : 30 protiens produced in the liver recruit phagocytes to infection & induce phagocytosis 3 main pathways: 1) Classical Pathway : Abs bind to an antigen on bug surface (APCs) 2) Alternative Pathway : no Abs involved complement components bind to bug surface for immune response recognition
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Players in the Complement Pathway: 1) C3A involved in vasodialation (mechanism is similar to an allergic response) ~ mechanism ~ increases permeability of blood vessels ~ helps get phagocytes to infected tissues ~ C3A = an anaphylatoxin 2) C3B opsonization (facilitates phagocytosis) (works like IgG) ~ mechanism : C3B binds to bug’s surface glycoproteins, then C3B is opsonized by receptors on the phagocytes facilitating phagocystosis 3) C5A recruits phagocytes & involved in vasodialation 4) MAC (membrane attack complex) C5B-C6-C9
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This note was uploaded on 04/08/2008 for the course MCDB 132 taught by Professor Mahan during the Spring '08 term at Santa Barbara City.

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MCDB 132 - HOST DEFENSES: First line: skin: nothing can...

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