ANALYSIS OF INTRAEPITHELIAL LYMPHOCYTES FROM MAJOR HISTOCOMPATIBILITYCOMPLEX (MHC)-DEFICIENT MICE - NO EVIDENCE FOR A ROLE OF MHC CLASS-IIANTIGENS IN THE POSITIVE SELECTION OF V-DELTA-4-DELTA T-CELLS(GAMMA)

Three-color flow cytometric analysis was carried out with intraepithel ial lymphocytes from mice deficient in expression of major histocompat ibility complex (MHC) antigens. These experiments were done to address the possible role of MHC class II molecules in the positive selection of Vdelta4+ gammadelta T cells. By analyzing mice deficient MHC class II antigens alone or in combination with MHC class I antigens, no evi dence was found for positive selection of Vdelta4+ cells among CD8alph a+ or CD4-CD8- subpopulations of gammadelta T cell receptor-positive c ells. Because Vdelta4+, CD8alpha+ cells were reported to be positively selected on I-E(k) and hybrid I-E(k/b) molecules, class II-deficient animals were crossed with I-E(k) transgenic mice and progeny examined for Vdelta4 expression. Again, no evidence for positive selection was found. Interestingly, in MHC class I-deficient animals, the total numb er of gammadelta T cells was about twofold higher than in control and MHC class II-deficient mice and the proportion of Vdelta4-expressing c ells was correspondingly decreased. Taken together, these results cast doubt on a major role for conventional MHC antigens in shaping the ga mmadelta T cell repertoire of intraepithelial lymphocytes.