Serological patterns of anti-HIV immune responses of 150 HIV-infected (65 asymptomatic, 19 ARC, 66 AIDS) and 150 HIV-negative healthy Zairians were studied to determine the clinical significance of p24 antigen, and anti-p24 antibody, particularly in relation to p24 relative binding capacity (RBC) and circulating immune complexes (CICs). Levels of p24 antigen, anti-p24 antibody titers, and p24 RBC were evaluated by means of enzyme-linked immunosorbent assay (ELISA). Circulating immune complexes were measured by C1q-binding assay. Human immunodeficiency virus CICs were detected by polyethylene glycol (PEG) precipitation followed by 6 M guanidinium lysis, ELISA, Western blot, or radioimmunoprecipitation of the lysed precipitates. Immunoglobulin levels for IgG, IgM, IgA, and beta 2-microglobulin (beta 2-M) were quantified in all study participants by laser nephelometry and ELISA. All immunoglobulin levels were significantly elevated among HIV-positive vs. HIV-negative individuals. Immunoglobulin levels correlated well with disease progression among infected patients. Similarly, beta 2-M levels were significantly higher in HIV-positive vs. HIV-negative individuals and correlated well with progression to AIDS. Free p24 antigen in serum was detected in 1.33% of all patients. However, p24 reactivity increased to 6% (9 of 150 cases) after PEG precipitation and CIC dissociation. There was a good correlation between p24 reactivity and disease development. High titers of anti-p24 antibody (> 44,100) occurred in at least 80% of all patients, and did not correlate with disease stage. Similarly, more than 60% of patients had high levels of p24 RBC.(ABSTRACT TRUNCATED AT 250 WORDS)