Plasma Cell Biology
المؤلف:
Mary Louise Turgeon
المصدر:
Immunology & Serology in Laboratory Medicine
الجزء والصفحة:
5th E, P64
2025-06-30
646
The function of plasma cells is the synthesis and excretion of immunoglobulins. Plasma cells are not normally found in the circulating blood but are found in the bone marrow in concentrations that do not normally exceed 2%. Plasma cells arise as the end stage of B cell differentiation into a large, activated plasma cell.
The pathway from the B lymphocyte to the antibody- synthesizing plasma cell forms when the B cell is antigenically stimulated and undergoes transformation because of the stimulation of various interleukins. The immune antibody response begins when individual B lymphocytes encounter an antigen that binds to their specific Ig surface receptors. After receiving an appropriate second signal provided by interaction with helper T cells, these antigen-binding B cells undergo transformation and proliferation to generate a clone of mature plasma cells that secretes a specific type of antibody.
An increase in plasma cells can be seen in a variety of nonmalignant disorders, such as viral disease (e.g., rubella, infectious mononucleosis), allergic conditions, chronic infections, and collagen diseases. In plasma cell dyscrasias, the plasma cells can be greatly increased or infiltrate the bone marrow completely (e.g., multiple myeloma, Waldenström’s macroglobulinemia).
Antibody molecules secreted by plasma cells consist of four chains—two light chains and two heavy chains, based on molecular weight—and can be enzymatically cleaved into Fab (antigen-binding) and Fc (crystallizable) fragments. The Fab portion binds antigen and contains the light chains and their antigenic markers (kappa, lambda), as well as heavy chains.
The Fc fragment contains the markers that distinguish the different classes of antibody and sites that will bind and activate complement and bind to Fc receptors on cells. The amino acid sequence for most of the antibody protein is constant, except for the antigen-binding portion of the molecule, which has a hypervariable region and accounts for the various antigenic specificities that the antibody is programmed to recognize.
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