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B lymphocyte

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Definition

noun, plural: B lymphocytes

A lymphocyte that is produced in the bone marrow and is responsible for the production of immunoglobulins and involved in the production of antibodies in the humoral immune response; a precursor of the plasma cell


Supplement

Lymphocytes are a type of white blood cells. They may be grouped into two: small and large lymphocytes. The small lymphocytes include B lymphocytes and T lymphocytes. The B lymphocytes are involved in the production of antibodies in the humoral immune response. The T lymphocytes participate in the cell-mediated immune response. The large lymphocytes include the natural killer cells.

B lymphocytes, or simply B cells, are a type of lymphocytes responsible for the production of immunoglobulins. Apart from this, they are also capable of releasing cytokines and acting as an antigen-presenting cell.

B lymphocytes can be identified from the other lymphocytes through protein receptors on the outer surface of the cell, and they are called B cell receptors (BCRs). The BCRs enable the B lymphocyte to bind to a specific antigen. Unlike T cells' receptors that connect to antigen on the cell surface of infected cells, the BCRs of the B cell can bind directly to the antigens on the surface of the pathogen (e.g. viruses, bacteria). Apart from this, the B cells have surface immunoglobins (IgM), which are absent on the surface of T cells. Despite their differences, they also have certain commonalities. For instance, both B cells and T cells are motile nonphagocytic cells with a large nucleus. They also morphologically similar. Thus, one cannot easily tell apart one from the other when viewed under a light microscope. The cell surface marker for most B cells is CD 19.

In birds, B lymphocytes mature in the bursa of Fabricius. This is from where its name ("B") was derived since it was first discovered in that particular bird's lymphoid organ. In mammals, they form and mature in the bone marrow.

The different types of B lymphocytes are as follows:


Word origin: French lymphe, from Latin lympha (water, water nymph), from Ancient Greek númphē (nymph) + New Latin cyta, from Ancient Greek kútos (vessel, jar)

Also called:

  • B cell

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