Critical Role of TCR Specificity in the Development of Vg1Vd6.3 Innate NKTgd Cells

Cells δ γ Innate NKT + 6.3 δ 1V γ Development of V A large fraction of innate NKTgd T cells uses TCRs composed of a semi-invariant Vd6.3/6.4-Dd2-Jd1 chain together with more diverse Vg1-Jg4 chains. To address the role of gdTCR specificity in their generation, we analyzed their development in mice transgenic (Tg) for a Vg1-Jg4 chain frequently expressed by NKTgd cells (Tg-g) and in mice Tg for the same Vg1-Jg4 chain together with a Vd6BDd2Jd1 chain not usually found among NKTgd cells (Tg-gd). Surprisingly, both promyelocytic leukemia zinc finger (PLZF) + and NK1.1 + NKTgd cells were found in the thymus of Tg-gd albeit at lower numbers than in Tg-g mice, and virtually all of them expressed the Tg TCR. However, the PLZF + subset, but not the NK1.1 + subset, also expressed an endogenous Vd6.3/6.4 chain, and its size was severely reduced in TCRd 2/2 Tg-gd mice. These results could suggest that the PLZF + and the NK1.1 + subsets are developmentally unrelated. However, PLZF + and NK1.1 + NKTgd cells express identical Vd6.3/6.4 chains, and NK1.1 + cells can be obtained upon intrathymic injection of sorted PLZF + cells, thus indicating their developmental relationship. In fact, the NK1.1 + gd thymocytes present in Tg-gd mice correspond to a small subset of NK1.1 + gd thymocytes in wild-type animals, which express a more diverse repertoire of TCRs and can be recognized by the expression of the CD62L Ag. Collectively, our data demonstrated that TCR specificity is essential for the development of most NKTgd T cells and revealed a developmental heterogeneity in gd T cells expressing the NK1.1 marker. M ouse T lymphocytes expressing NK lineage cell markers, usually referred to as NKT lymphocytes, constitute a diverse population of cells with unique characteristics that place them at the interface between innate and adaptive immune systems. The numerically most important population correspond to cells bearing TCRs, which recognize glycolipids presented by the nonclassical MHC-I molecule CD1d on cortical thymocytes. More than 80% of these TCRs are composed of an invariant (i)Va14-Ja18 TCRa-chain that associates with a limited number of Vb-chains (usually referred to as iVa14 NKT cells or type I NKT cells) and that are commonly identified by their binding to a-galactosylcer-amide–loaded CD1d tetramers. The remaining 20% represent a collection of rare but recurrent Va3.2-Ja9, Va8 TCRa-chains frequently associated with Vb8 chains and other TCRs and are referred to as …