ANTIBODIES AND IMMUNOGLOBULINS
Antibodies—The Secreted Products of Plasma Cells
Antibodies are synthesized and secreted primarily by plasma cells, the progeny of B lymphocytes. Since many different clones of cells participate in the immune responses to a single antigen, antibodies are heterogeneous with respect to their structure and function. However, proteins carrying antibody activity, all of which migrate electrophoretically as γ-globulins, belong to different immunoglobulin classes (ie, IgG, IgA, IgM, IgD, and IgE).All immunoglobulins are composed of two polypeptide chains of different molecular size, the light and heavy chains. A monomeric immunoglobulin molecule consists of two heavy and two light chains. These polypeptide chains are arranged in the shape of a Y (Fig 20-1). The arms of the Y are composed of the amino-terminal halves of the heavy chain and the entire light chain, while the carboxyterminal halves of the two heavy chains constitute the stem. The arms and the
Bloch KJ, Salvaggio JE. Use and Interpretation of Diagnostic Immunologic Laboratory Tests. JAMA. 1982;248(20):2734–2758. doi:10.1001/jama.1982.03330200158029
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