Identification of antigenic components of Toxoplasma gondii by an immunoblotting technique.

Proteins of Toxoplasma gondii were separated by SDS-polyacrylamide gel electrophoresis with subsequent transfer to a nitrocellulose sheet by electrophoretic blotting. Immunologically reactive polypeptides were detected by human sera with previously known toxoplasma antibody levels. Heavy chain-specific, peroxidase-conjugated anti-human immunoglobulins were used as the indicator antibodies for the separate identification of IgG and IgM reactive polypeptides. IgG toxoplasma antibodies reacted with several antigens of Mr approximately 27 000-67 000, while toxoplasma-specific IgM seemed to detect only a few polypeptides. The Mr of 35 000 for the dominating IgM reactive polypeptide was observed.