Anti-CD4 activity in circulating immune complexes in HIV-infected patients.

Levels of circulating immune complexes (CIC) measured by precipitation with 1.04 M ammonium sulfate ranged from 22 to 2,040 micrograms/ml in a group of 141 HIV-infected patients. CIC were elevated (> 200 micrograms/ml) in 72.2% of infected individuals. When analyzed for their HIV antigen composition, those CIC containing HIV antigens were found more frequently in patients clinically affected (68.6%) than in asymptomatic individuals (31.4%; p < 0.001). Anti-CD4 activity of 89 isolated CIC was detected in 43.8% of these patients, but only in 7.6% of the cases these CIC could bind to native CD4+ molecules. CIC with anti-CD4 activity could inhibit PHA stimulation of normal peripheral blood lymphocytes. Anti-CD4 activity in CIC was independent of the clinical and immunological status of HIV-infected patients.