Cytotoxic T cell responses to haptenated cells II. On the role of H-2 genes

Cytotoxic T cell (CTL) responses to cells coupled with high or low doses of the hapten 3-(p-sulfophenyldiazo)-4-hydroxyphenyl acetic acid (SP) were studied. CTL responses to densely coupled cells were obtained with all mouse strains tested. Only mice carrying the K^k allele responded to sparsely coupled cells. Mice expressing I-A^kbut not K^k were nonresponders. (Responder × nonresponder) F₁ hybrids responded in vitro to sparsely coupled cells from responder but not from nonresponder mice. However, responder mice could be cross-primed in vivo with SP-coupled cells from nonresponder mice. CTL responding to sparsely coupled cells were restricted to K^k. Cross-reactive lysis of target cells not carrying the K^k allele was dependent on the hapten density and the H-2 haplotype carried by the target cells.