青岛大学基础医学院医学免疫学

1、Section 1 membranous molecules on B lymphocyte and functions 一、一、B cell receptor ，BCR Constitution of BCR complex： mIg（IgM and IgD）and Ig （CD79a） /Ig （CD79b） 1、mIg Structure：mIg consist of a basic unit of four polypeptide chains,two identical H chains and two identical L chains. Intracellular region

2、 is very short. immature B cells express mIgM， mature B cells express mIgM and mIgD simultaneously， plasma cells dont express Ig. Function：specific binding antigen 2、Ig /Ig Structure ： Ig （CD79a）and Ig （CD79b） belong to Ig gene surperfamily，consist of extracellular region，transmembrane region and cy

3、toplasma 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 cell 2、 transferring Ig from inner of cell to outer of cell Distribution of BCR complex： nmature B cell and immature B cell

4、 npre-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. 1 2 1314151617 18 19 20 3 45 6789 11 1210 Lymphocytes have unique, clonally distributed antigen receptors 1010 1010101

5、0 101010101010 101010101010 Antibodies B cells 1、CD19/CD21/CD81/CD225 and ： 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, iC3b function：enhance the sensitivity of B cell to antigen stimulus 2、CD72 Contain 2 ITIM nLi

6、gand： Constituent expression on mature B cell B T CD27 CD70 CD70 CD27 innate immunity，play a role in mucous membrane immunity Antigen of stimulating ： LPS （ lipid polysaccharides ） Production antibody：IgM Polyreactivity ： Similarities and differences of B-1 cell and B-2 cell LocationPeritoneum/pleur

7、aEverywhere RenewalSelf renewalBone marrow Spontaneous Ig productionHighLow Polyreactivity Isotypes Somatic hypermutation of IgNo Immunity to Immunity to Carbohydrate Immunity to Protein Section 3 function of B cell （一）（一）produce antibodies 1、 neutralization: bacteria toxin ,pathogen 2、 opsonization

8、： Ab、complement 3、antibody-dependent cell-mediated cytotoxicity（ADCC） 4、 activate Complement : opsonization and lyse microbe （二）（二）antigen presenting ： activated B cells presenting soluble Ag （三）（三）immunoregulation ： positive and negative regulation Distribution of BCR complex： nmature B cell and immature B cell npre-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. LocationPeritoneum/pleuraEverywhere RenewalSelf renewalBone marrow Spon