Plasma cell

Plasma cells, also called effector cells are cells of the immune system and are used for production and secretion of antibodies. They correspond to the final stage of differentiation of the B cell lineage and appear in the light microscope as a large oval cells with eccentric gelegenem nucleus. The importance of plasma cells for the production of antibodies was described in 1948 by the Swedish immunologist Astrid Fagraeus part of her doctoral work.

The lifespan of plasma cells varies from a few days or weeks up to highly durable plasma cells. Through contact with the antigen B cells are activated and differentiate beyond the stage of so-called plasmablasts to plasma cells. While plasma blasts are still capable of division, but already secrete antibodies differentiated plasma cells no longer divide terminal.

If antigen -presenting B cells encounter in the T cell zone of the lymph nodes on specific helper T cells that recognize the presented antigen, they are activated. Then they form a primary focus and differentiate into antibody-producing plasma cells. Some of the B cells that have been activated in this way by T- cell help, hiking in Primary lymphoid follicles and form a so-called germinal center. B cells that have been activated by T cell - independent antigens, germinal center formation is denied it. It comes in these T - cell - independent activated B cells not to affinity maturation, and the isotype will not be consummated. The antibodies produced are always of the IgM - type. It is not for memory formation.

In germinal center B cells undergo affinity maturation and isotype switching to produce a plasma cell high-affinity antibodies of different immunoglobulin classes. A part of the B- cells do not develop into plasma cells, but also to memory B cells. The memory cells in turn mediate immunological memory for this antigen. The formation of such memory cells, for example, the necessary condition for a successful vaccination. Memory cells can be rapidly activated and differentiate into plasma cells, which results in an accelerated and increased second immune response when re- encounter with the antigen. Moreover, they are already very affine by their mutations in membrane-bound antibody for the antigen. In addition to the memory cells are formed in the germinal center and plasma cells with high-affinity antibodies of different classes. These migrate to a large extent in the bone marrow, where they can stay for a long time to receive survival signals from the bone marrow stromal cells and secrete antibodies.

Plasma cells can be characterized by the expression of surface markers such as CD19, CD38 and CD138 ( human). Previously it was assumed that the expression of CD19 after migration is lost to the bone marrow, but these hints from experiments with multiple myeloma, ie cancer - derived plasma cells. However, recent studies point to a CD19 expression on terminally differentiated plasma cells.

Plasma cells have a lot of cytoplasm and many layers of the endoplasmic reticulum to synthesize large quantities of antibodies. They do not express MHC - II and more can the T-helper cells thus present no signal. Surface immunoglobulins are still expressed in small amounts.