Signalling through TEC kinases regulates conventional versus innate CD8(+) T-cell development.

Recent data from three laboratories have identified the TEC kinases, ITK and RLK, as crucial regulators of CD8(+) T-cell development into the conventional lymphocyte lineage. In the absence of ITK and RLK, CD4(+)CD8(+) thymocytes upregulate the T-box transcription factor eomesodermin, and develop into mature CD8(+) T cells that resemble memory cells, exhibit immediate effector cytokine production and depend on IL-15. Furthermore, the selection of these non-conventional 'innate' T cells results from interactions with haematopoietic cells in the thymus. These findings lead to the hypothesis that altered TCR signalling, together with distinct co-stimulatory signals, is the basis for the development of non-conventional T-cell lineages.