Anti-IgG autoantibodies in HIV-infected hemophilia patients

Sera of 76 HIV-negative hemophilia patients, 103 HIV-positive (HIV+) hemophilia patients free of AIDS or AIDS related complex (ARC), and 32 HIV+ hemophilia patients with AIDS/ARC were tested for four different anti-IgG activities. IgG-anti-F(ab')2γ, IgM-anti-F(ab')2γ, and IgG-anti-Fcγ serum activities were significantly associated with the clinical stage of HIV infection, whereas IgM-anti-Fcγ was not. IgG-anti-F(ab')2γ activity was found to be caused by cross-reaction of anti-HIV antibody with an epitope within the constant CHI domain of human IgG. HIV+ hemophilia patients with severe thrombocytopenia ( 50,000/μl platelets. Because anti-IgG antibodies possess immunoregulatory properties, our results may serve as a possible explanation for the frequent B cell disorders encountered in HIV-infected patients.