Membrane Receptors for IgG and Complement (C4, C3b and C3d) on Human Eosinophils and Neutrophils and Their Relation to Eosinophilia

Abstract

Abstract Receptors have been shown, on human eosinophils and neutrophils, for rabbit IgG, human IgG, and human C4, C3b and C3d. Both types of granulocyte formed rosettes with EArabG. This was directly related to the amount of sensitizing antibody. No rosettes were formed with E alone or EArabM Receptors for human IgG were also demonstrated by using heat-aggregated IgG and fluorescent-labeled anti-human IgG. In addition, aggregated human IgG inhibited both eosinophil and neutrophil rosettes with EArabM. Red cell intermediates were prepared with EArabM (EA) and functionally pure human complement components. Eosinophil and neutrophil rosette formation was demonstrable with EAC14 and EAC1423b, prepared with limited amounts of C4 (EAC3b), and was related directly to the input of either C4 or C3. No granulocyte rosettes were formed with EAC1 or EAC142. By decay experiments it was shown that C2, in addition to forming the classical pathway C3 convertase with C1 and C4, also inhibited eosinophil and neutrophil EAC14 rosettes. EAC3d intermediates (prepared by treating EAC3b cells with the C3b inactivator and so rendering them immune adherence negative, unsusceptible to lysis with C5–C9 and more agglutinable with anti-C3d) formed rosettes with eosinophils and neutrophils in comparable numbers to EAC3b cells. In general, the percentage of neutrophils bearing receptors for rabbit IgG, human IgG, or human C4, C3b, and C3d was approximately two and one-half times greater than eosinophils. There was a significantly reduced percentage of eosinophils forming rosettes with EAC14 or EAC3b when patients with eosinophilia of various etiology were compared to controls; however, no differences were found with EArabG. When neutrophils from patients with eosinophilia were compared to controls in terms of percentage of EArabG, EAC14, or EAC3b rosettes, there were no significant differences. These results, taken together with previously published findings on the monocyte, suggest that all circulating phagocytic cells have similar membrane receptors for promoting adherence of opsonized particles and that with eosinophils the numbers of complement receptors may be altered in disease.