B细胞及B细胞介导的免疫应答.ppt

* * * * * * * * * 主要针对细胞外病原体 * TD-Ag和TI-Ag * * * * * * * * * * * * * * * * * * * * * The interactions of Th cells and B cells in lymphoid tissues The anatomy of humoral immune responses Downloaded from: StudentConsult (on 1 June 2006 03:50 PM) ? 2005 Elsevier Mechanisms of Th cell-mediated activation of B cells B cell-mediated immune response The edge of lymphoid follicle Fully activation Th cells → CD40L cytokines Formation of germinal center Affinity maturation point mutations in the V regions Heavy chain class switching different Ab heavy chain classes Key point “Second signal” Site: GC (germinal center) 2. Th cell-mediated activation and differentiation of B cells Germinal center Function: to generate B cells that produce antibodies with affinity maturation Germinal Center Reaction: Activated B cells give rise to Centroblasts （中心母细胞） - localize in follicle, undergo rapid cell division and turn on machinery that causes somatic mutation in V-regions Centroblasts give rise to Centrocytes （生发中心细胞） - migrate to the FDC-rich region of the Germinal Center - survival is dependent on interaction with FDC-bound Ag and presentation of Ag to Tfh cells - centrocytes that successfully compete to bind antigen (e.g. by having higher affinity BCR) and to receive Tfh cell help are selected and may differentiate into long-lived plasma cells or memory B cells Germinal center Ch. 11 p. 294 Fully activation Th cells → CD40L cytokines Formation of germinal center Affinity maturation point mutations in the V regions Heavy chain class switching different Ab heavy chain classes Key point “Second signal” Site: GC (germinal center) 2. Th cell-mediated activation and differentiation of B cells The anatomy of humoral immune responses ? Affinity maturation is the process by which the affinity of Abs produced in response to a protein Ag increase