[Antibody differentiation in human toxoplasmosis experiments on model cases (author's transl)].

Human sera with antibodies against Toxoplasma gondii were investigated-before and after gel filtration (Sephadex G 200)-by IgM-and IgG-specific immunofluorescent reactions as well as well by complement fixation tests.-In sera from patients with "latent" infections IgM-antibodies could not be demonstrated neither by the IgM-IFT-nor the CFT technique, although IgG antibodies with IFT titres between 1:50 qnd 1:200 were present.-In sera from patients in the "acute" stage of infection both IgM and IgG antibodies were always found. In some cases the IgG fraction had complement fixing properties only, although IgM antibodies were present as demonstrable by the IFT technique. -These observations leed to the possibility of immunologic differentiation between IgM-IFT and CF-antibodies. The role of the different antibodies in the serodiagnosis of human toxoplasmosis is discussed.