DISTINCT SPLICING OF CD45 MESSENGER-RNA IN ACTIVATED RAT GAMMA-DELTA CYTOTOXIC T-LYMPHOCYTES

Previous studies have demonstrated tumor- and allo-specific cytotoxic gamma delta T lymphocytes in rats. In this report we define the surfac e phenotype of these T cell receptor (TCR) gamma delta(+) T cells and demonstrate distinct CD45 mRNA splicing in activated gamma delta cytot oxic T lymphocytes (CTL). gamma delta T lymphocytes in the blood and t he peritoneal cavity were TCR alpha beta(-)CD3(+)CD8 alpha(+)CD45RC(+) but expressed variable levels of LFA-1 molecules. Normal peritoneal g amma delta T lymphocytes, peritoneal gamma delta T cells from rats inj ected with the bacterial superantigen staphylococcal enterotoxin A (SE A) as well as gamma delta T lymphocytes in peripheral blood were ah LF A-1(low). Peritoneal gamma delta T cells from tumor-, and allo-sensiti zed rats were either LFA-1(low) or LFA-1(high) and specific cytotoxici ty was highly enriched in the LFA-1(high) subset. No cytolytic activit y against SEA-presenting cells was recorded in gamma delta T cells fro m SEA-injected rats. Different isoforms of CD45 in T cells are generat ed by alternative mRNA splicing of exons 4, 5, 6 (or A,B and C, respec tively) and the recently described alternate exon 7. CD45 splicing in sorted ya T cells was evaluated utilizing reverse transcription polyme rase chain reaction. Normal peritoneal ya T cells expressed exon(578), exon(678), exon(78) and the extensively spliced exon(8) variant. Peri toneal gamma delta T cells from rats sensitized with irradiated syngen eic tumor cells, allogeneic cells or bacterial superantigen SEA as wel l as gamma delta T lymphocytes in peripheral blood contained the full- length exon(45678), as well as the exon(5678), exon(578), exon(678) an d exon(78) splicing products. Notably, the exon(8) variant was also se en in peritoneal gamma delta T cells of SEA-sensitized rats. Sorted tu mor-specific LFA-1(high) gamma delta CTL expressed exon(45678), exon(5 678), exon(578), exon(678) and exon(78) CD45 splicing products whereas the non-cytolytic LFA-1(low) gamma delta T cell subset also contained exon(8) variant. In summary, it is concluded that antigen-specific TC R gamma delta(+) CTL express high levels of LFA-1 and that the splicin g machinery in these cytolytic cells favors expression of the exon(456 78) and exon(5678) CD45 splicing products whereas the exon(8) variant is lost. TCR alpha beta(+) CTL express high levels of LFA-1 but are de void of the full-length exon(45678) splicing product. The different CD 45 splicing patterns found in ap CTL and ya CTL indicate different mol ecular requirements in respect to CD45 during activation and different iation of these T lymphocyte subsets.