B cell receptor signaling pathway

Each B-Cell is specific for a particular antigen. The specificity of binding resides in the B-Cell receptor (BCR) for antigen. They are integral membrane proteins. They are present in thousands of identical copies exposed at the cell surface. They are made before the cell ever encounters an antigen. B-Cell receptor complex usually consist of an antigen-binding subunit and a signaling subunit.

BCRs have a unique binding site. This site binds to a portion of the antigen called an antigenic determinant or epitope. The binding depends on complementarity of the surface of the receptor and the surface of the epitope. In the absence of specific antigen, mature B-Cells survive in the peripheral circulation for only a few days. Cells which do not encounter antigen within this period of time undergo apoptosis. Most B-Cells require direct contact by TH lymphocytes as well as exposure to TH lymphocyte cytokines in order to be fully activated.

The signal initiated by binding of antigen to the B-Cell receptor complex causes growth and proliferation of the B-Cell and the creation of an amplified clone of effector cells that secrete the antigen-specific immunoglobulin. Activation of the B-Cell receptor by antigen also results in the production of memory cells that persist in circulation to produce a more rapid immune response after future challenges by the same antigen. The bound antigen molecules are engulfed into the B-Cell by receptor-mediated endocytosis. The antigen is digested into fragments, which are then displayed at the cell surface nestled inside a class II histocompatibility molecule

Click gene symbol on the map to view ORF/cDNA clone.

Data source: KEGG, BioCarta