Lecture 4-DCs

Lecture 4-DCs - Innate Immune System PHAGOCYTOSIS Antigen...

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Innate Immune System PHAGOCYTOSIS
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Antigen degradation is most potent in innate immune cells that primarily control infection by killing (macrophages and neutrophils) Antigen processing is more regulated, and is generally carried out by DCs to initiate adaptive immune responses
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Professional antigen presenting cells (APC) Generally express CD11c, but levels of expression vary among subsets Two classes: conventional (cDCs) and plasmacytoid (pDCs); different cell lineages. cDCs are the primary subset that present antigens to T cells. pDCs are generally involved in immune surveillance for viral infection- make type I interferons
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DCs are found in most epithelial surfaces. They are immature tissues and mature to present antigens to T cells (and B cells) upon antigen recognition and migration to lymph nodes
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MHCII (green); lysosome (red) Immature DC in periphery Highly phagocytotic MHCII co-localized with lysosome Intermediate DCs after antigen exposure migrate to lymph nodes and stop phagocytosing. Captured antigen is internal. Mature DCs in lymph nodes do not phaogcytose; instead they display captured antigen to T cells within MHC complexes
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T cells leave the bloodstream and enter lymph node through HEVs into the paracortical space. DCs with antigen are in the paracortex and interact with T cells
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Lymph nodes near site of infection upregulate surface molecules on innervating blood vessels to recruit lymphocytes. This step is constitutive (unlike during infections) and accumulates T and B cells of different receptor clonality to increase probability of encountering the correct antigen-MHC and TCR
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T cells that have the correct antigen receptor remain in the lymph node for extended periods of time to become activated. T cells with the incorrect TCR leave through efferent lymphatics back into the circulation
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This note was uploaded on 01/03/2012 for the course BI 144 taught by Professor List during the Fall '10 term at Caltech.

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Lecture 4-DCs - Innate Immune System PHAGOCYTOSIS Antigen...

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