Lymphotoxin-Mediated Regulation of gamma delta Cell Differentiation by alpha beta T Cell Progenitors

The thymus gives rise to two T cell lineages, alpha beta and gamma delta , 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 super(+) and CD8 super(+) alpha beta T cells. Instead we report that DP cells regulate the differentiation of early thymocyte progenitors and gamma delta cells, by a mechanism dependent on the transcription factor RORgt, and the lymphotoxin (LT) beta receptor (LT beta R). 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.