Multiple constraints at the level of TCRa rearrangement impact Vα14i NKT cell development

CD1d-restricted NKT cells that express an invariant V alpha 14 TCR represent a subset of T cells implicated in the regulation of several immune responses, including autoimmunity, infectious disease, and cancer. Proper rearrangement of Va14 with the J alpha 18 gene segment in immature thymocytes is a prerequisite to the production of a TCR that can be subsequently positively selected by CD1d/self-ligand complexes in the thymus and gives rise to the NKT cell population. We show here that V alpha 14 to J alpha rearrangements are temporally regulated during ontogeny providing a molecular explanation to their late appearance in the thymus. Using mice deficient for the transcription factor ROR gamma and the germline promoters T early-a and J alpha 49, we show that developmental constraints on both V alpha and J alpha usage impact NKT cell development. Finally, we demonstrate that rearrangements using Va14 and Ja18 occur normally in the absence of FynT, arguing that the effect of FynT on NKT cell development occurs subsequent to a-chain rearrangement. Altogether, this study provides evidence that there is no directed rearrangement of Va14 to Ja18 segments and supports the instructive selection model for NKT cell selection.