Presentation of Class I antigens on T cells can induce the generation of antigen-specific CTL

Cytotoxic T lymphocyte (CTL) lines generally require a source of specific antigen to continue to proliferate in vitro. We previously showed that populations of mononuclear cells grown in medium containing interleukin 2 (IL 2) and composed largely of activated T cells were able to present Class I alloantigen to CTL lines. On the basis of these findings we were interested to know whether T cells themselves were able to present antigen or whether this was a function of the small number of contaminating non-T cells. To answer this question, populations of activated or resting mononuclear cells were rigorously depleted of non-T cells before use as antigen-presenting cells. We observed that populations composed of greater than 99% T cells were able to support the differentiation of antigen-specific CTL. These results were confirmed by using cells from an established T cell line. The proliferation of the same lines, however, was less than that of lines grown in the presence of antigen-presenting cells containing some non-T cells. These results suggest that although T cells can present Class I alloantigens to CTL, they may be less effective in triggering cell division than populations containing a source of non-T cells.