Activated human T cells can present denatured antigen.

The requirements for activated, Ia-positive human T cells to present antigen were examined. Although activated T cells could present allo-Ia antigens, activated T cells could not present native, soluble protein antigens. We have now shown that activated T cells can present denatured protein antigens to stimulate proliferation of antigen-specific T-cell lines. Since denatured antigen may represent a processed form of antigen, the data suggest that activated T cells can present antigen but may not be able to process antigen as efficiently as other presenting cells. We have also shown that antigen-specific T-cell lines, which are also Ia positive, are able to present antigen to themselves, if the antigen is in a denatured form. Autopresentation requires a critical minimal cell number to stimulate proliferation, even with denatured antigen. The ability of activated T cells to present antigen may reflect an important amplification or feedback mechanism of immune regulation.