Hypocomplementemia and human immunodeficiency virus infection. Clinical correlates and relationships to circulating immune complex and immunoglobulin G levels.

The levels of C4 and C3 were measured and related to other immunological and clinical parameters in 44 patients with the human immunodeficiency virus (HIV) infection. Circulating immune complexes (C1q-CIC) as measured by an enzyme-linked immunosorbent assay employing monoclonal antibody with specificity for bound Clq, and serum immunoglobulin G (IgG) concentrations were assessed simultaneously. Clinical parameters assessed included: (1) the presence of specific anti-infective medications; (2) the presence of hypotension and fluid administration, and (3) bacterial and specific opportunistic infections. Hypocomplementemia was observed in 25 of 46 sera for C3, and in 8 of 46 sera for C4. Clq-CIC increases were seen in 26 of 46 sera and hyper-IgG was present in 25 of 46 sera. Lower C3 concentrations were significantly associated with elevated Clq-CIC levels (p less than 0.001). There were significant correlations between Clq-CIC levels and C3 concentrations (p = 0.0065, negative) and IgG levels (p = 0.0075, positive). Clq-CIC were significantly higher with serum p-24 antigen levels of 50 pg/ml or greater. These data demonstrate that elevated Clq-CIC and hypocomplementemia are both common in HIV-infected patients and may have significant relationships.