Characteristics of T-cell receptor V alpha 24J alpha QT cells, a human counterpart of murine NK1(+) T cells, from normal subjects

Background: In mice, natural killer (NK)T cells are specialized subsets of T cells that express an invariate T cell receptor (TCR) a chain and NK mark ers. In particular, murine NK1(+/-) T cells rapidly produce IL-4 and functi on as regulatory T cells. Objective: We investigated the distribution of invariate TCR V alpha 24J al pha Q T cells in CD4(-)CD8(-) double-negative (DN) and CD4(+) T cell popula tions of healthy individuals, We also studied the NK phenotypes and IL-4 pr oduction of Va24JaQ T cells. Methods: The frequency of V alpha 24(+/-) DN or CD4+ T cells was determined by three-color FAGS analysis, and subsequently the frequency of Va24JaQ re arrangement among V alpha 24(+/-) DN or CD4(+) T cells was determined by se quencing. Results: While the majority of DN V alpha 24(+) T cells (68% to 88%) posses sed TCR V alpha 24J alpha Q, few of CD4(+) V alpha 24(+) T cells (0.4% to 4 %) did, indicating that V alpha 24J alpha Q T cells are a major population of DN T cells, but not of CD4(+) T cells, in healthy subjects. The DN Va24J aQ T cells expressed a natural killer surface receptor NKR-P1A and CD56, bu t not CD16, on the cell surface. Moreover, DN V alpha 24J alpha Q T cells p romptly expressed IL-4 mRNA by stimulation with anti-V alpha 24 monoclonal antibody in vitro. Conclusion: From these phenotypic and functional similarities of human DN V alpha 24J alpha Q T cells with murine NK1(+) V alpha 14J alpha 281 T cells , we conclude that DN Va24JaQ T cells are a counterpart of murine NK1+ T ce lls, suggesting that they may play a regulatory role in autoimmune response s in vivo.