![]() ![]() ![]() Most of these B cells will become plasmablasts (or "immature plasma cells"), and eventually plasma cells, and begin producing large volumes of antibodies. Germinal center B cells may differentiate into memory B cells or plasma cells. Upon stimulation by a T cell, which usually occurs in germinal centers of secondary lymphoid organs such as the spleen and lymph nodes, the activated B cell begins to differentiate into more specialized cells. First, the B cells must encounter a foreign antigen and are then required to be activated by T helper cells before they differentiate into specific cells. This is a type of safeguard to the system, similar to a two-factor authentication method. These T cells bind to the MHC II-antigen molecule and cause activation of the B cell. Pieces of the antigen (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). Development Īfter leaving the bone marrow, the B cell acts as an antigen-presenting cell (APC) and internalizes offending antigens, which are taken up by the B cell through receptor-mediated endocytosis and processed. ![]() Compared with CD138, which disappears rapidly ex vivo, the expression of CD319 is considerably more stable. It is also expressed on malignant plasma cells in multiple myeloma. This antigen is expressed at high levels on normal human plasma cells. Īnother important surface antigen is CD319 (SLAMF7). The surface antigen CD138 (syndecan-1) is expressed at high levels. In humans, CD27 is a good marker for plasma cells naïve B cells are CD27−, memory B-cells are CD27+ and plasma cells are CD27++. Instead, plasma cells are identified through flow cytometry by their additional expression of CD138, CD78, and the Interleukin-6 receptor. Terminally differentiated plasma cells express relatively few surface antigens, and do not express common pan-B cell markers, such as CD19 and CD20. Other organelles in a plasma cell include ribosomes, lysosomes, mitochondria, and the plasma membrane. Abundant rough endoplasmic reticulum combined with a well-developed Golgi apparatus makes plasma cells well-suited for secreting immunoglobulins. Their cytoplasm also contains a pale zone that on electron microscopy contains an extensive Golgi apparatus and centrioles ( EM picture). They have basophilic cytoplasm and an eccentric nucleus with heterochromatin in a characteristic cartwheel or clock face arrangement. Plasma cells are large lymphocytes with abundant cytoplasm and a characteristic appearance on light microscopy. Structure Plasma cells with Dutcher and Russell bodies ( H&E stain, 100×, oil) B cells differentiate into plasma cells that produce antibody molecules closely modeled after the receptors of the precursor B cell. These antibodies are transported from the plasma cells by the blood plasma and the lymphatic system to the site of the target antigen (foreign substance), where they initiate its neutralization or destruction. Plasma cells, also called plasma B cells or effector B cells, are white blood cells that originate in the lymphoid organs as B lymphocytes and secrete large quantities of proteins called antibodies in response to being presented specific substances called antigens. ![]()
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