HumoralImmunity

HumoralImmunity - \ Humoral Immunity A. Thymus Dependent...

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· \ Humoral Immunity A. Thymus Dependent (TO) Response a) B2 cells predominant (IgM10lgOhiCOS-) b) Requires T helper cells No response in athymic mice (nude mice) c) Typically elicits a germinal center response Somatic hypermutation Affinity maturation Class switching Memory B cell B. Thymus Independent (TI) Response a) Responses observed in nude mice b) TI-type 1 response B1 cells (IgMhilgOIOCOS+) c) TI-type 2 response Marginal zone B cells (lgMhilgOIOCDS-)
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Humoral Immunity Primary Response r~ after immuCliutioo DUld.(ioCl of A(tainmcn( of Lag Phasc Pak Rcspons<: Erythrocytes 3--4 days -4-5 days Soluble pro(cins 5-7 days 9-10 days Baet<:ria 10-1-4 days 2~3 weeks Toxoid >3wceks <3 mon(hs Secondary Response c ~ ... c . v c :3 ... ~ c -< .. , ... .. "" I I . . .. . I .: . l€G .... 1 ~ J 21\·. . 11\
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Capillary endothelium .,.;'~ (. :.'" .:Ii--- ~ A¢t~4ted 'matUm' ' djlndritiO ¢ell" Afferent lymph Chemokines orchestrate the trafficking of dendritic cells, T cells and B cells needed to generate an immune response. By activating TlRs, LPS on the surface of bacterial pathogens ctimulates the local release of chemokines such as MIP-la, MIP·lp, MIP-3a and IP-IO.lmmature dendritic cells are attracted to this site through activation of chemokine receptors, such as CCRI, CCR5 and CCR6, that they constitutively express. Immature dendritic cells are efficient at picl<ing-op antigen, but muct mature and differentiate into ceKs that can activate naive T cells, The local milieu into which the immature dendritic cell is attracted contains pathogen-associated molecular patterns (e,g, LPS) that are recognized by PRRs such as CDl4 and TLRs, which induce the differentiation and maturation of dendritic cells into potent antigen- presenting cells. During this process, the dendritic cell downregulates expression of CCR 1, CCR5 and CCR6 and upregulates expression of CCR7, causing its migration into the afferent lymphatic system. The CCR7 ligand SLC, which is expressed on the endothelium of the afferent lymphatic system, plays an important role in directing the migration of the antigen-loaded mature dendritic cells, Chemokines are Current OpInion In 'mrnunoIol1Y also involved in bringing naive T cells and B cells from blood across high endothelial venules (HEVs) into the lymph nodes and into contact with the activated dendritic cell_ The molecular details remain to be elucidated, but it is likely that chemokines such as DC-CK1 and ELC are important in juxta-positioning these cells in the lymph node. SlC and ELC are produced from stromal cells in the T-<;ell zone and BlC is expressed from stromal cells in the B-cell follicle, helping to guide cells to T- and B-cef1 areas, respectively. Some activated T cells downregulate expression of CCR7 but upregulate CXCR5 and so become directed toward the follicle to deliver help to B cells, whereas other activated T cells upregulate CXCR3 and are attracted into inflamed tissue. T cells that are activated in regional lymph nodes, after
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HumoralImmunity - \ Humoral Immunity A. Thymus Dependent...

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