Binding of human IgA1 to rat peritoneal macrophages.

In the present study we have investigated whether bovine erythrocytes (Eb) specifically sensitized with human polyclonal IgA l (EbIgA 1) are able to bind to resident adherent rat peritoneal cells (PMø). Rat PMø formed rosettes with Eb-IgAl at room temperature and at 37°. The formation of these rosettes could be blocked completely by excess human serum IgA or myeloma IgAl. In contrast, human IgG or rat IgG did not inhibit the formation of rosettes, whereas human polymeric myeloma IgA2 only partially inhibited rosette formation. Complete inhibition of rosette formation was also induced by rat monomeric and polymeric myeloma IgA, suggesting species interchangeability. Furthermore, rosette formation could be completely blocked in the presence of excess asialofetuin or D-galactose, while excess ovalbumin or D-mannose had no effect. These results suggest that the oligosaccharides in the hinge region of human IgAl are involved in the binding of Eb-IgAI to rat PMø. [ABSTRACT FROM AUTHOR]