Suppression by IgA of IgG-mediated phagocytosis by human polymorphonuclear leucocytes.

Abstract

IgA from normal human serum, a myeloma IgA and human colostral IgA were found to inhibit the IgG-dependent phagocytosis of Candida albicans (CA) blastospores by polymorphonuclear leucocytes (PMN) from normal human subjects. The inhibition was dependent on the Fc portion of IgA, was enhanced by heat treatment (56°C for 20 min) and depended on binding to the PMN, but not to the opsonized particle. Binding of CA to the PMN IgG Fc receptor was inhibited, whilst the binding to the PMN C3b receptor was unaffected.