Immunoblot analysis of Toxoplasma gondii antigens by human immunoglobulins G, M, and A antibodies at different stages of infection.

The Toxoplasma gondii antigenic components eliciting the immunoglobulin G (IgG), IgM, and IgA antibody responses were studied by using follow-up sera from a laboratory worker who developed an acute glandular toxoplasmosis after an accidental infection with the protozoa. IgG toxoplasma antibodies reacted with multiple components over a wide molecular weight range from 6,000 to 150,000. In contrast, IgM toxoplasma antibodies reacted predominantly with polypeptides of 6, 25, and 35 kilodaltons, which might be useful in new diagnostic procedures. The general pattern of antigenic components in the IgA toxoplasma antibody response closely resembled that in the IgM response, even though some characteristic features were constantly observed. The possibility that the restricted IgM and IgA antibody responses relate to the pathogenetic events in human toxoplasmosis is considered.