CD8+ T cells rapidly acquire NK1.1 and NK cell-associated molecules upon stimulation in vitro and in vivo

NKT cells express both NK cell-associated markers and TCR, Classically, these NK1.1(+)TCR alpha beta(+) cells have been described as being either CD4(+)CD8(-) or CD4(-)CD8(-). Most NKT cells interact with the nonclassical MHC class I molecule CD1 through a largely invariant V alpha 14-J alpha 281 TCR chain in conjunction with either a V beta 2, -7, or -8 TCR chain. In the present study, we describe the presence of significant numbers of NK1.1(+)TCR alpha beta(+) cells within lymphokine-activated killer cell cultures from wild-type C57BL/6, CD1d1(-/-), and J alpha 281(-/-) mice that lack classical NKT cells. Unlike classical NKT cells, 50-60% of these NK1.1(+)TCR alpha beta(+) cells express CD8 and have a diverse TCR V beta repertoire. Purified NK1.1(-)CD8 alpha(+) T cells from the spleens of B6 mice, upon stimulation with IL-2, IL-4, or IL-15 in vitro, rapidly acquire surface expression of NK1.1. Many NK1.1(+)CD8(+) T cells had also acquired expression of Ly-49 receptors and other NK cell-associated molecules. The acquisition of NK1.1 expression on CD8(+) T cells was a particular property of the IL-2R beta(+) subpopulation of the CD8(+) T cells. Efficient NK1.1 expression on CD8(+) T cells required Lck but not Fyn, The induction of NK1.1 on CD8(+) T cells was not just an in vitro phenomenon as we observed a 5-fold increase of NK1.1(+)CD8(+) T cells in the lungs of influenza virus-infected mice. These data suggest that CD8(+) T cells can acquire NK1.1 and other NK cell-associated molecules upon appropriate stimulation in vitro and in vivo.