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B cellsZoomA-Z

Subject - Immunology

B cells (B lymphocytes) are the antibody-producing cells of the immune system. Every B cell produces only one type of antibody, which is directed against a specific epitope.

The production of antibodies begins when the B cell has recognized its specific antigen and has simultaneously been stimulated with cytokines by a T helper cell that has also recognized the antigen. The B cell, which is still immature, then begins to divide (one cell division every 18 hours) and to build up the cell apparatus for protein biosynthesis. A B cell that has fully matured after 4-5 days is called a plasma cell; 90-95 % of the proteins it produces are antibodies. It secretes up to 2,000 antibodies every second (20,000 mRNA for 200,000 ribosomes per cell).

After this type of immune reaction, some B cells remain in a late, inactive, pre-plasma cell state. With renewed antigen contact, these memory B cells can mature into plasma cells much faster to battle the antigen with antibodies within a much shorter time span. Memory B cells are an important part of the immunological memory formed upon vaccination.

The "B" in B cell is derived from bone marrow, which is where the B cells are formed from blood stem cells.

See also: T cells , antigen-presenting cells

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