Immunology 5 - Immunology 5 Adaptive vs Innate Receptors...

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Immunology 5 Adaptive vs Innate Receptors Receptor Characteristic Innate Adaptive Specificity inherited in the genome Yes- germ line No Expressed by all cells of a particular type Yes No Triggers immediate response No-14 days Recognizes broad classes of pathogens Yes-degenerate patterns No Interacts with a range of molecular structures of a given type Yes-PAMPS No Encoded in multiple segments No Requires gene arrangement No Clonal distribution No Able to discriminate between even closely related molecular structure No After entering tissues, many pathogens are recognized, ingested and killed by phagocytes 3 major classes of phagocytic cells in innate immune system: macrophages and monocytes, granulocytes and dendritic cells Macrophages mature continuously from monocytes→ major phagocyte population resident in normal tissues→different tissues=different names=found in large numbers in connective tissues Granulocytes= neutrophils(greatest phagocytic activity and most immediately involved), eosinophils and basophils Neutrophil= polymorphonuclear neutrophilic leukocytes=short lived=abundant in blood but not present in healthy tissue Dendritic cells=resident in tissues= arise from both myeloid and lymphoid progenitors within bone marrow= **primary role in immune defence is not front-line large scale direct killing of microbes 2 main functional types of dendritic cells Conventional dendritic cells= process ingested microbes to generate peptide antigens that can activate T cells and induce adaptive immune response, and to produce cytokines in response to microbial recognition=bridge between innate and adaptive immune response Plsmacytoid dendritic cells= major producers of the antiviral interferons and are considered to be part of the INNATE immunity Macrophages in submucosal tissues are the first cells to encounter pathogens but are soon reinforced by neutrophils=recognize pathogens by means of cell surface receptors that can discriminate between surface molecules of pathogens and those of host Phagocytosis= receptors on surface bind to component of microbial surface→ bound pathogen surrounded by plasma membrane and then internalized by a large membrane enclosed vesicle (phagosome) →phagosome becomes acidified which kills most pathogens→ phagosome fuses with lysosome to generate a phagolysosome where lysosomal contents are released to destroy pathogen Neutrophils= highly specialized for intracellular killing of microbes=contain cytoplasmic granules which fuse with phagosome and contain enzymes and antimicrobial peptides Receptor mediated endocytosis= extracellular material taken up=not restricted to phagocytes Macropinocytosis= performed by DC and other phagocytes=take up pathogens non-specifically Some phagocytes also signal through other pathways to trigger responses such as cytokine production→ include receptors from C-type lectin-like family: Dectin-1=
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This note was uploaded on 02/08/2012 for the course PATHOLOGY 3245 taught by Professor X during the Spring '11 term at UWO.

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Immunology 5 - Immunology 5 Adaptive vs Innate Receptors...

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