Tumorigenicity of adenovirus-transformed rat cells and expression of class I major histocompatibility antigen

The expression of class I major histocompatibility antigens was studied in six syngeneic adenovirus 12 (Ad12)-transformed LIS rat cell lines of varying tumorigenicity. The concentration of MHC class I product was estimated by indirect immunofluorescence staining of viable cells in suspension with specific antibody and cytofluorographic analysis, and by sensitivity to killing by allogeneic cytolytic T cells (CTLs) elicited by immunization with spleen cells in vivo and in mixed lymphocyte reactions in vitro. None of the rat cell lines examined was devoid of MHC class I antigen. When compared to syngeneic Ad2-transformed cells or fibroblasts, the average intensity of fluorescence of Ad12-transformed lines was lower, suggesting that the concentration of MHC class I antigen is somewhat lower in Ad12-transformed cells. Sensitivity to killing by both in vivo and in vitro induced allogeneic CTLs, however, was not markedly lower with Ad12-transformed cells and correlation was not found between tumorigenic potential in vivo and sensitivity to allogeneic T-cell killing in vitro.