Clonal analysis of cytolytic T lymphocyte specificity. I. Phenotypically distinct sets of clones as the cellular basis of cross-reactivity to alloantigens.

Abstract

The cellular basis of the cytolytic cross-reactivity observed in primary allogeneic (C56BL/6 anti-DBA/2 and C57BL/6 anti-C3H/He) [mouse] mixed-leukocyte cultures (MLC) was investigated by analysis of the specificity of clonal progeny derived from individual cytolytic T lymphocyte (CTL) precursor cells (CTL-P) contained within these populations. A sensitive mixed-leukocyte microculture (micro-MLC) technique was used with limiting dilution analysis by Poisson statistics to determine the frequency of CTL-P reactive against specific and 3rd-party ([mouse mastocytoma] P815 and [mouse lymphoma] AKRA) target cells, to caluclate the probability that each micro-Mlc was a clone derived from a single CTL-P and to examine the specificity of each micro-MLC assayed separately against both target cells. A total of 287 phenotypically specific, heteroclitic and cross-reactive micro-MLC from the 2 different strain combinations were observed with a relative frequency of 81, 11 and 8%, respectively, and were calcuated to have mean clone probabilities of 90 and 99% when based, respectively, upon the frequencies of CTL-P reactive against the specific and 3rd-party target cells. These clones were estimated to have an approximate size of 6 .times. 104 cells, which roughly corresponded to 16 cell doublings during the 7 days of culture. A total of 22 clones were successfully subcloned and, in virtually every case, the subclones retained the specificity phenotype of the original clone from which they were derived. Direct evidence for 3 phenotypically distinct sets of CTL as the cellular basis of cross-reactivity in MLC populations assayed against 2 different target cells was provided.