Lymphotoxin-mediated regulation of γδ cell differentiation by αβ T cell progenitors

The thymus gives rise to two T cell lineages, alphabeta and gammadelta, that are thought to develop independently of one another. Hence, double positive (DP) thymocytes expressing CD4 and CD8 coreceptors are usually viewed simply as progenitors of CD4(+) and CD8(+) alphabeta T cells. Instead we report that DIP cells regulate the differentiation of early thymocyte progenitors and gammadelta cells, by a mechanism dependent on the transcription factor RORgammat, and the lymphotoxin (Lt) beta receptor (LTbetaR). This finding provokes a revised view of the thymus, in which lymphoid-tissue induction-type processes coordinate the developmental and functional integration of the two T cell lineages.