Both human and mouse cells expressing H-2Kb and ovalbumin process the same peptide, SIINFEKL.

HeLa cells, derived from a human cervix carcinoma line, were transfected with a mouse MHC class I gene, H-2Kb, and chicken ovalbumin. H-2Kb-restricted cytotoxic mouse T cells specific for ovalbumin recognized the double-transfected human cells with similar efficiency as ovalbumin-transfected EL4 mouse thymoma cells (H-2b). The naturally processed ovalbumin T cell epitope was eluted from H-2Kb molecules from double-transfected HeLa cells and was biochemically compared to a synthetic peptide, SIINFEKL, known to be the natural Kb ligand of ovalbumin-transfected H-2b mouse cells. The results indicate that the ovalbumin-derived Kb-ligand of double-transfected HeLa cells is also SIINFEKL. Thus, both human cervix carcinoma cells and mouse thymoma cells expressing Kb and ovalbumin process the same octapeptide. Together with previous data, derived by comparing Kb ligands of unknown sequences from both human and mouse cells expressing Kb, it can be concluded that both mouse and human cells are capable of processing the same ligands for mouse MHC class I molecules. Hence, the general specificity of the peptide-generating mechanism for class I ligands is apparently conserved between evolutionary distant species.