Limit-dilution analysis of weak influenza-immune T cell responses associated with H-2Kb and H-2Db.

A limiting-dilution analysis has been made of influenza-immune cytotoxic T lymphocyte (CTL) response patterns associated with H-2Kb and H-2Dd in the B10.A(5R), and H-2Kk and H-2Db in the B10.A(2R) and B10.A(4R) recombinant mouse strains. In previous in vivo experiments the H-2Kb allele has been shown to be associated with low responsiveness or nonresponsiveness, whereas Db-restricted influenza-specific responses were found to be weak in recombinant strains that possessed the Kk allele. Influenza-immune CTL restricted to the more "dominant" H-2Dd and H-2Kk alleles were found consistently when primed T cells were restimulated in vitro under limiting-dilution conditions. Precursors were present at frequencies of at least twice background levels (lysis of normal targets) in the great majority of experiments, performed with or without added helper factors. The H-2Kb- and H-2Db-restricted responses were much more variable and, for H-2Kb but not for H-2Db, were completely absent when the culture medium did not contain added interleukin preparations. Even so, experiments in which individual microcultures were tested on more than one target demonstrated conclusively both that H-2Kb-restricted CTL can be generated under limiting-dilution conditions and that most, if not all, of these T cells do not cross-react with influenza virus presented in the context of H-2Dd. The characteristics of these "weak" responses are thus that they are more help dependent and show evidence of greater variability between individual mice than the "dominant" CTL clones do.