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Functional Assays for B Cells and Antibodies, Page 1 of 2
< Previous page Next page > /docserver/preview/fulltext/10.1128/9781555815905/9781555813642_Chap37-1.gif /docserver/preview/fulltext/10.1128/9781555815905/9781555813642_Chap37-2.gifAbstract:
The function of the humoral immune response differs depending on the class of antibody produced and the differentiation state of the B cell. Primary defects in the humoral components of the immune response are usually recognized by clues as frequent development of infections early in life and difficulty in clearance of infections. The most direct measure of in vivo B-cell function is immunoglobulin secretion by plasma cells. Serum immunoglobulins are most commonly measured by automated nephelometry. Antibodies provide protection to the host in various ways. Antibodies can neutralize toxins (e.g., tetanus toxin), neutralize viruses, prevent the adhesion of bacteria to the host cells, kill bacteria in the presence of complement, and opsonize bacteria for phagocytes. Generally, the complement-mediated bactericidal mechanism does not kill gram-positive bacteria, although there are exceptional cases. This mechanism is primarily relevant in the study of antibodies to gram-negative bacteria, which have thin walls. Opsonophagocytosis is the primary protective mechanism of antibodies against gram-positive bacteria. Various methods have been developed to measure the opsonizing capacity of antibodies in vitro. The classical approach is to perform an opsonophagocytic killing assay. In this assay, the bacteria are opsonized (coated) with antibodies and complement. The increased use of functional assays has shown the importance of standardization.