Hypocomplementemia and Human Immunodeficiency Virus Infection

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-CΙC) as measured by an enzyme-linked immunosorbent assay employing monoclonal antibody with specificity for bound C1q, 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. C1q-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 C1q-CIC levels (p < 0.001). There were significant correlations between C1q-CIC levels and C3 concentrations (p = 0.0065, negative) and IgG levels (p = 0.0075, positive). C1q-CIC were significantly higher with serum p-24 antigen levels of 50 pg/ml or greater. These data demonstrate that elevated C1q-CIC and hypocomplementemia are both common in HIV-infected patients and may have significant relationships.