Hematologic correlates and the role of erythrocyte CR1 (C3b receptor) in the development of AIDS.

Circulating immune complexes (CICs) are common in patients with the acquired immunodeficiency syndrome (AIDS) as in anemia. In our previous reports, we observed that the deposition of CICs on erythrocytes via C3b receptors (CR1) resulted in a defective CIC clearing system of erythrocytes and in high membrane osmotic fragility of such erythrocytes. We investigated the functional activity of erythrocyte CR1 in 89 patients with AIDS, 41 with AIDS related complex (ARC), 102 healthy homosexual volunteers, and 37 heterosexual males, in relation to the presence of CICs, antibody to lymphadenopathy associated virus/human T lymphotropic virus-III (LAV/HTLV-III), anemia, and the direct and indirect Coombs' tests. CICs were frequently found in all groups except heterosexual males. Absence of CR1 activity was observed in 85% of patients with AIDS, and in 59% with ARC. Impaired CR1 activity also occurred in the homosexual volunteer group. Positive direct Coombs' test and the presence of CICs correlated inversely with CR1 activity while a lowered hematocrit and the presence of antibody to LAV/HTLV-III correlated directly. Neither the sera nor the eluates from erythrocytes with a positive IgG Coombs' test contained IgG antibody against erythrocytes. This suggests decremental loss of CR1 activity progressing from asymptomatic LAV/HTLV-III antibody positive homosexual volunteers to the prodromal spectrum of ARC and finally progressing to a total disappearance in overt AIDS. Of 8 homosexuals volunteers demonstrating the composite of impaired CR1 activity, positive antibody to LAV/HTLV-III, and polyvalent positive direct Coombs' test (with gamma, mu, and C3b), all developed ARC or overt AIDS within 2 years of these observations.