Evaluation of immunoblotting for the detection of Toxoplasma gondii immunoglobulin M antibodies.

Immunoblot analysis was used to detect human IgM antibodies to Toxoplasma gondii in 20 patients with recent toxoplasmosis, 30 immune individuals, 30 non-immune individuals, and 24 children less then two years old. Analysis of the IgM strips revealed that specific IgM antibodies detectable after a recent Toxoplasma gondii infection react with the same antigens as the 'natural' antibodies present in the sera of immune and non-immune individuals and in the sera of young children. These data indicate that immunoblotting is not useful as a reference method for Toxoplasma gondii IgM detection, and suggest that improvement of the specificity of IgM detection will remain difficult.