Human T lymphocyte clones reactive in primed lymphocyte typing and cytotoxicity

The human HLA-D region, the presumed evolutionary homologue of the H–2 I region in mouse and similar genetic regions in other species1, codes for multiple antigenic determinants, a finding consistent with the existence of multiple loci2,3. One method developed to define D region encoded determinants is primed LD typing (PLT) wherein cells of one individual are primed in vitro in a mixed leukocyte culture (MLC) to allogeneic HLA-D encoded determinants associated with one haplotype4,5. The PLT cells give a rapid proliferative response when restimulated in secondary culture with either the priming cells or third party cells that carry the priming antigen(s). However, as in many cases a PLT cell is probably primed to several determinants, different restimulating cells from unrelated individuals will engender a range of responses varying from very high to very low, presumably depending on the number of determinants shared (or cross-reactive) between the priming and restimulating cells. Such results are difficult to interpret in terms of defining antigenic determinants on the cells of various individuals. Fathman and Hengartner6 have circumvented this problem in mouse by cloning murine T lymphocytes from multiply restimulated PLT cells; the progeny of any one clone give highly specific proliferative responses. We report here the use of the supernatant of phytohaemagglutinin (PHA)-stimulated mixtures of human allogeneic cells7,8 (designated T-cell growth factor or TCGF) to grow ‘clones’ of human T lymphocytes following alloactivation in MLC. Clones that give PLT-type responses do so in a highly antigen-specific manner. Following cloning, cells in many cases have undergone 25 or more divisions, thus yielding in excess of 1×108 progeny.