RECOGNITION OF TARGET CELL DETERMINANTS ASSOCIATED WITH DLA-D-LOCUS-ENCODED ANTIGENS BY CANINE CYTOTOXIC LYMPHOCYTES

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Abstract
Cytotoxic lymphocytes (CTL) were generated in bulk mixed leukocyte culture (MLC) using peripheral blood mononuclear cells from homozygous dogs identical to each other for DLA-A and -B but different for DLA-D loci. These CTL were tested against 51Cr-labeled targets (Con-A-stimulated PBMC) derived from the MLC sensitizing dogs and from other dogs homozygous for various DLA-D locus alleles. Indirect cell-mediated lympholysis (CML) assays, with and without cold target blocking and pretreatment of 51Cr-labeled targets with DLA alloantisera were used to study the target cell determinants recognized by these CTL. The resultant target cell lysis and cold target blocking of specific target cell lysis indicated target determinants associated with DLA-D-locus-encoded specificities, and different from those encoded by DLA-A and -B loci. The pattern of shared target determinants among different DLA-D HTC may be explained by: (A) two separate previously unrecognized MHC associated loci, each with 2 alleles defined so far; or (B) epitopes shared among certain DLA-D alleles but not present in others. This study demonstrates that DLA-D associated determinants different from previously described DLA-D specificities may serve as CML target cell determinants when there are no apparent DLA-A and -B loci encoded antigen differences between responder and stimulator cells used to generated MLC-derived CTL.