Distinct splicing of CD45 mRNA in activated rat γδ cytotoxic T lymphocytes

摘要

AbstractPrevious studies have demonstrated tumor‐ and allo‐specific cytotoxic γδ T lymphocytes in rats. In this report we define the surface phenotype of these T cell receptor (TCR)γδ+T cells and demonstrate distinct CD45 mRNA splicing in activated γδ cytotoxic T lymphocytes (CTL). γδ T lymphocytes in the blood and the peritoneal cavity were TCRαβ−‐CD3+CD8α+CD45RC+but expressed variable levels of LFA‐1 molecules. Normal peritoneal γδ T lymphocytes, peritoneal γδ T cells from rats injected with the bacterial superantigen staphylococcal enterotoxin A (SEA) as well as γδ T lymphocytes in peripheral blood were all LFA‐1low, Peritoneal γδ T cells from tumor‐, and allo‐sensitized rats were either LFA‐1lowor LFA‐1highand specific cytotoxicity was highly enriched in the LFA‐1highsubset. No cytolytic activity against SEA‐presenting cells was recorded in γδ T cells from SEA‐injected rats. Different isoforms of CD45 in T cells are generated by alternative mRNA splicing of exons 4, 5, 6 (or A, B and C, respectively) and the recently described alternate exon 7. CD45 splicing in sorted γδ T cells was evaluated utilizing reverse transcription polymerase chain reaction. Normal peritoneal γδ T cells expressed exon(578), exon(678), exon(78) and the extensively spliced exon(8) variant. Peritonealγδ T cells from rats sensitized with irradiated syngeneic tumor cells, allogeneic cells or bacterial superantigen SEA as well as γδ T lymphocytes in peripheral blood contained the full‐length exon(45678), as well as the exon(5678), exon(578), exon(678) and exon(78) splicing products. Notably, the exon(8) variant was also seen in peritoneal γδ T cells of SEA‐sensitized rats. Sorted tumor‐specific LFA‐1highγγ CTL expressed exon(45678), exon(5678), exon(578), exon(678) and exon(78) CD45 splicing products whereas the non‐cytolytic LFA‐1lowγδ T cell subset also contained exon(8) variant. In summary, it is concluded that antigen‐specific TCRγδ+CTL express high levels of LFA‐1 and that the splicing machinery in these cytolytic cells favors expression of the exon(45678) and exon(5678) CD45 splicing products whereas the exon(8) variant is lost. TCRαβ+CTL express high levels of LFA‐1 but are devoid of the full‐length exon(45678) splicing product. The different CD45 splicing patterns found in αβ CTL and γδ CTL indicate different molecular requirement