中科院细胞与分子免疫学课程课件9.ppt

* * * * * * * * * 2.2 Selection of High- Affinity B Cells There Fc receptor and completment C3b/C3d receptor on the FDC surface. The receptor can present the antigen to B cell. There are also soluble form antibody in the germinal center. Only the high-affinity B cells to the antigen can survie. 3 Generation of Memory B cells and Secondary Humoral Immune Responses Some activated B cells do not develop into antibody secretors. Instead, they acquire the ability to survive for long periods without antigenic stimulation. Some memory B cells remain in the lymphnode. Others circulate in the blood. Antibody Responses to T Cell – Independent Antigens ? Thymus-dependent antigen Thymus-independent antigen Chemical nature  ??????????????????????????????????????????????????  ??????????????????????????????????????????????????????????????? Features of antibody response ? Isotype switching  ??????????????????????????????????????????????????????????????????????????????????????????????????  ????????????????????????????????????????????????????????????????????? Affinity maturation Yes Little or no Secondary response (memory B cells) Yes Only seen with some antigens (e.g., polysaccharides) Ability to induce delayed-type hypersensitivity Yes No Antibody Feedback: Antigen-antibody complexes was formed The complexes can simultaneously bind to antigen receptors and Fcg receptor II The Fcg receptor II contain ITIM The signal was blocked 上堂课回顾： B细胞的激活： 与T细胞类似，B细胞的激活 1、BCR复合体：IgM和IgD，Iga 和 Igb。 2、激活途径： 酪氨酸激酶Lyn, Blk 和 Fyn使Iga 和 Igb的ITAM磷酸化，Syk蛋白结合到磷酸化的ITAM基序上，并被活化。进一步募集SLP－65蛋白，此蛋白结合Grb2蛋白和Sos蛋白，激活Ras－MAP途径；此蛋白结合PLCg，则激活IP3和DAG途径。 * * * * * * * * * * * * * * * * * * * * * * * * * * * Chapter 9 B Cell Activation and Antibody Production General Features of Humoral Immune Responses 1. Sequential phases are needed in the process of activation of B cells to produce antibody. 2. Whether antibody responses to antigen require CD4+ helper T cells depends on the antigen character. 3. Activa