Cytofluorographic analysis of receptors for IgA on human polymorphonuclear cells and monocytes and the correlation of receptor expression with phagocytosis

Abstract

Receptors for the Fc portion of IgA (RFcα) were identified on human monocytes and polymorphonuclear cells (PMNs) by cytofluorograph analysis using FITC-labeled IgA and by rosette formation with IgA-sensitized indicator cells. Larger percentages of PMNs obtained from the oral cavity expressed RFca than did blood PMNs. These oral PMNs also expressed more RFcα per cell than blood PMNs. Moreover, the expression of these receptors on blood PMNs was enhanced by overnight incubation with IgA. In functional studies, RFcα appeared to cooperate with receptors for IgG in enhancing blood and oral PMN mediated phagocytosis of target cells coated with IgG and IgA. Furthermore, and in contrast with blood PMNs, oral PMNs were capable of phagocytosing target cells coated with IgA alone. Thus, receptors for IgA may be important to the ability of RFca bearing effector cell populations to mediate protection at mucosal surfaces.