青岛大学基础医学院医学免疫学.pptxVIP

青岛大学基础医学院医学免疫学第1页/共31页第2页/共31页Section 1 membranous molecules on B lymphocyte and functions 一、B cell receptor ，BCR Constitution of BCR complex：mIg（IgM and IgD）and Ig?（CD79a）/Ig ?（CD79b）第3页/共31页第4页/共31页1、mIgStructure：mIg consist of a basic unit of four polypeptide chains,two identical H chains and two identical L chains.Intracellular region is very short. immature B cells express mIgM， mature B cells express mIgM and mIgD simultaneously，plasma cells don’t express Ig. Function：specific binding antigen 第5页/共31页2、Ig?/Ig? Structure ： Ig?（CD79a）and Ig? （CD79b）belong to Ig gene surperfamily，consist of extracellular region，transmembrane region and cytoplasma region，Ig? and Ig? held together by disulfide bond to form heterogenous dimer,then form BCR-Ig?/Ig? complex with BCR. Function：1、 transducing antigen-binding signal to B cell2、 transferring Ig from inner of cell to outer of cell第6页/共31页Distribution of BCR complex：mature B cell and immature B cellpre-B receptor consists of ?chain、substitute L chain and Ig?/Ig? ， pre-B receptor expressing on the surface of pro-B cell，is really important for B cell development in bone marrow.第7页/共31页第8页/共31页101010101010101010101010101010101010AntibodiesLymphocytes have unique, clonally distributed antigen receptorsB cells2016131415171918453296871111012第9页/共31页二、co-receptor1、CD19/CD21/CD81/CD225Structure and Distribution ：The co-receptor on the surface of B cell is composed of CD19、CD21 and CD81/CD225（Leu-13）with non-covalent bond.ligand：C3dg , C3d, iC3bfunction：enhance the sensitivity of B cell to antigen stimulus第10页/共31页第11页/共31页2、CD72Structure: Belongs to C-type lectin superfamily, is a 45kDa II-type transmembranous protein. Distribution:Constituent expression on every stage B cells except plasma cells. Contain 2 ITIMLigand：CD100,expressed on most hemocytoblast including B and T cells. CD100 interacting with CD72 can eliminate the inhibition by CD72，enhancing the effect of signal 1 . Function:When BCRs cross link, it can inhibit the s