Limit dilution cultures were used to test for influenza immune T cell populations from bm1 and bm3 mutant mice that were not lytic for virus-infected targets expressing the Kb and Db major histocompatibility complex glycoproteins. Both Kbm3- and Kbm1-restricted cytotoxic T cells were detected. Such effectors showed minimal cross-recognition of influenza on other mutant targets, except for the case of bm1 and bm10 targets. This is dissimilar to previous findings concerning vaccinia presentation in which bm3+bm11, bm1+bm9, and bm3+bm9 pairs each showed high cross-reactivity. These differences illustrate the role of the H-2K glycoprotein in immune responsiveness. Not only are multiple determinants on each H-2K glycoprotein involved in antigen presentation, they appear to play differential roles in the presentation of different viral antigens.