Murine Asialo GM1+CD8+ T Cells as Novel Interleukin-12-responsive Killer T Cell Precursors

Freshly isolated CD8+ T cells, but not CD4+ T cells, contained 20–30% of asialo GM1+ (ASGM1+) T cells which were distinct from ASGM1+NK1.1+ natural killer cells. This novel ASGM1+CD8+ T cell subpopulation showed a strong proliferative response to interlenkin-12 (IL-12) in the presence of IL-2. Culture of ASGM1+CD8+ T cells with IL-12 plus IL-2 allowed the generation of anomalous killer T cells concomitantly with the accumulation of cytolytic molecules. Moreover, ASGM1+CD8+ T cells produced high levels of interferon-γ (IFN-γ), but not IL-4, upon stimulation with IL-12 plus IL-2. Such immune responses were not observed in ASGM1− CD8+ T cell snbpopulations constituting the majority of CD8+ T cells. These results demonstrated that ASGM1+CD8+ T cells are a novel subpopulation of IL-12-responsive and IFN-γ-producing killer T cell precursors.