Interaction of Antisera to the Secretory Component with FcαR
The predominant immunoglobulin (Ig) in human external secretions is secretory IgA (SIgA) (1) which appears to be produced largely by IgA-containing plasma cells underlying the mucosal epithelium (1,2). IgA is unique in that two distinct receptors for the Fc portion of the molecule exist, the secretory component (SC) and the Fc receptor for IgA (FcaR) (3). SC is a glycoprotein associated with the epithelial cells lining mucosal surfaces (4), and functions both as a receptor for polymeric IgA and IgM and as a transport molecule in the translocation of Igs across secretory epithelium into exocrine fluids (4,5). The FcaR has been reported to be present on both B and T lymphocytes, monocytes and polymorphonuclear leukocytes (PMN) in a number of species (3). While the role of I FcaR on these cells is not clear, there is evidence that T cells which express membrane-bound Fc receptors may regulate Ig production in an isotype- specific manner both in vivo and in vitro. In some cases, this regulation is mediated via the release of soluble, isotype-specific Ig binding factors from FcR+ T cells (3).
KeywordsCell Surface Molecule Murine Cell Human Peripheral Blood Lymphocyte Secretory Component Rosette Formation
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