Hypocomplementemia and human immunodeficiency virus infection. Clinical correlates and relationships to circulating...

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.