Relationship between the HLA Associated Specificities 4a and 4b and the Lymphocyte C3 Receptor

Abstract

Contrary to previous reports, we have obtained no evidence that 4a and 4b antisera specifically inhibit C3 rosette formation by human lymphocytes. Pretreatment of lymphocytes with various whole 4a and 4b antisera resulted in partial inhibition which was often nonspecific. Ultracentrifugation of the sera to remove immune complexes removed C3 rosette inhibitory activity although specific cytotoxic activity remained. It is probable that immune complexes in antisera will have fixed C3 which will have been converted to C3d and so be able to block the C3d receptor. This is the receptor mainly measured in these and in the previous experiments.

The Blocking Effect of Antibodies Against the Products of the H‐2 Gene Complex on Lymphocyte Complement (C3d) Receptors. Complement Dependence and Specificity

“…Galili et al (1977) report blocking also by antisera against other I-ILA antigens, and the pattern of the blocking effects was reported to correlate with the pattern of cytotoxicity reactions on the tested individuals. On the other hand, Frew & Bright (1977) were not able to obtain the specific blocking by anti-Bw4 and anti-Bw6 sera, and all blocking activity of these antisera was abolished after ultracentrifugation which removed immune complexes. Similarly, Ferreira e t al.…”

“…The relationship between the complement receptors (C3b and C3d) and the products of the major histocompatibility system (MHS) was studied using somatic cell hybrids (Curry et al 1976) and by the blocking effects of anti-H-2 or anti-HLA sera on the formation of rosettes with antibody and complement coated erythrocytes (EAC) (Arnaiz-Villena & Festenstein 1975, Frew & Bright 1977, Galili et al 1977, Ferreira et al 1976).…”