What is the established physiological function of IgD? ______________?
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Answer: A. Antigen recognition by B cells
Explanation
Immunoglobulin D is expressed primarily on the surface membrane of mature naive B lymphocytes. In this location, it functions alongside membrane IgM as an essential antigen receptor. Antigen binding to surface IgD triggers B cell activation and subsequent immune responses. Immunoglobulins are specialized glycoprotein molecules produced by plasma cells during immune responses. IgD circulates in very low concentrations in blood plasma compared to other antibody isotypes. Its primary biological role centers on regulating B cell development and antigen recognition.
Immunologists study surface marker expression to track B cell maturation stages in clinical assays. While secreted IgD plays a minor role, membrane-bound IgD is critical for adaptive immunity. Understanding B cell receptors helps explain how the immune system recognizes diverse foreign antigens. Localization protection in external secretion describes the primary function of secretory IgA antibodies. Compliment activation is a major biological effector function mediated by IgM and IgG antibodies. Reagin activity is a historical term associated with IgE antibodies mediating allergic reactions.
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