Development
After leaving the bone marrow, the B cell acts as an antigen presenting cell (APC) and internalizes offending antigens. That antigen is taken up by the B cell through receptor-mediated endocytosis and processed. Pieces of the pathogen (which are now known as antigenic peptides) are loaded onto MHC II molecules, and presented on its extracellular surface to CD4+ T cells (sometimes called T helper cells). These T cells bind to the MHC II/antigen molecule and cause activation of the B cell. Upon stimulation by a T cell, which usually occurs in germinal centers of secondary lymphoid organs like the spleen and lymph nodes, the activated B cell begins to differentiate into more specialized cells. Germinal center B cells may differentiate into memory B cells or plasma cells. The mechanism by which a B cell becomes one or the other of these three is a process known as affinity maturation. Most of these B cells will become plasmablasts, and eventually plasma cells, and begin producing large volumes of antibodies.
Read more about this topic: Plasma Cell
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