title: Studies on immune adherence (C3b) receptor activity of human erythrocytes: relationship between receptor activity and presence of immune complexes in serum.
abstract: Human erythrocytes (E) have surface receptors for the third component of complement (C3b-IA receptors) which mediate immune adherence haemagglutination (IAHA). We have observed that E from patients with systemic lupus erythematosus had imparied or defective C3b receptor (C3b-R) activity when circulating immune complexes (CIC) were found in serum. This phenomenon has been investigated by a newly developed method involving competitive inhibition of IAHA in patients with immune complex diseases. IAHA involving sheep E coated with antibody and complement (EAC), and indicator human E was inhibited by lysates of E with normal C3b-R activity from healthy donors and a monkey. In contrast, the lysates of E from 95% of patients bearing CIC did not inhibit IAHA, which indicated such E had defective or impaired C3b-R activity. This phenomenon was supported by control studies in which IAHA was not inhibited by lysates of E with absent, inactivated or occupied C3b-R. In those patients, in whom CIC disappeared during immunosuppressive therapy, C3b-R activity slowly returned to normal levels. Moreover, it was observed that C3b-R activity of patients' E decreased with the reappearance of CIC during exacerbations of disease. These observations suggest that CIC are carried in vivo by the C3b-R of E as well as those of the mononuclear phagocyte system, and that the E C3b-R may also contribute to the clearance of CIC.
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex / Q000032:analysis*; D003179:Complement C3b / Q000378:metabolism*; D003165:Complement System Proteins / Q000032:analysis; D006224:Cricetinae; D004285:Dogs; D004912:Erythrocytes / Q000276:immunology*; D006168:Guinea Pigs; D000882:Haplorhini; D006801:Humans; D007104:Immune Adherence Reaction; D007105:Immune Complex Diseases / Q000276:immunology*; D007074:Immunoglobulin G / Q000032:analysis; D008180:Lupus Erythematosus, Systemic / Q000276:immunology; D011817:Rabbits; D011951:Receptors, Complement / Q000378:metabolism*; D012756:Sheep
chemical_list: D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D011951:Receptors, Complement; D003179:Complement C3b; D003165:Complement System Proteins