Localization of the Trypanosoma cruzi-specific Mr 25,000 antigen by immune electron microscopy using monoclonal antibodies.

Two monoclonal antibodies reacted with the Trypanosoma cruzi-specific antigen of an apparent Mr 25,000 from all developmental forms (Tachibana et al. 1986). This T. cruzi-specific antigen was found at the plasma membrane by immunoperoxidase electron microscopy using the monoclonal antibodies TCF48 and TCF87. The TCF48 and TCF87-treated cells showed stain deposits at the plasma membrane clearly distinguishable from those in cells treated with a monoclonal antibody against a surface antigen. This suggests that the epitope(s) of the Mr 25,000 antigen is located on the inner surface or in the matrix of the plasma membrane. TCF48 and TCF87 also reacted with an antigen on the microtubules of the axoneme, but not with the subpellicular microtubules. These results suggest that the T. cruzi-specific Mr 25,000 antigen is common to both the plasma membrane and axoneme but it is not located at the subpellicular microtubules. Its identity and that of the surface antigen, Gp25 (Scharfstein et al. 1983) as well as its role in the pathogenicity of the parasite are discussed.