Isotypes and IgG subclasses of anti-Fab antibodies in human immunodeficiency virus-infected hemophilia patients.

We reported recently that anti-Fab autoantibodies of the IgG isotype are associated with the decrease of helper/inducer (CD4+) lymphocytes in human immunodeficiency virus-infected (HIV+) hemophilia patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC). In the present study we investigated the subclass distribution of IgG-anti-Fab autoantibodies, and whether anti-Fab antibodies of the IgA and IgM isotypes also are associated with the development of AIDS. Sera of HIV+ patients with AIDS had significantly higher IgA-anti-Fab activity than HIV+ patients with ARC (p < 0.02), HIV+ patients without AIDS/ARC (p < 0.0001), HIV-negative (HIV-) patients (p < 0.001), or healthy controls (p < 0.0001). An inverse association was found between IgA-anti-Fab activity and CD4+ cell counts (r = -0.396, p < 10(-6)). In contrast, no association of CD4+ cell counts was observed with IgM-anti-Fab. However, IgM-anti-Fab was significantly increased in patients with thrombocytopenia. We found a significant association between IgA-anti-Fab activity and serum neopterin concentrations (r = 0.310, p < 10(-5)). IgG-anti-Fab activity was detected mainly in the IgG3 fraction, although in HIV+ patients with AIDS/ARC various IgG subclasses were present. Affinity-purified anti-Fab antibodies isolated from sera of AIDS patients bound to rgp120-preincubated CD4+ cells of a healthy individual, supporting our hypothesis that anti-Fab antibodies and free circulating gp120 molecules are involved in the elimination of uninfected CD4+ cells. Removal of anti-Fab autoantibodies from the circulation by immune adsorbance might be a useful approach in the treatment of AIDS.