Murine thymic NK cells: A case of identity

Just over a decade ago, it was established that NK cells in the thymus do not follow precisely the same developmental pathway as conventional NK cells that develop in the bone marrow. Subsequently, it has emerged that NK cells are one branch of a family of innate lymphoid cells (ILCs). ILC1s and thymic NK cells have, however, sufficient similarities such that questions have been raised about how distinctive each cell type is from the other. In this issue of European Journal of Immunology, Gabrielli et al. [Eur. J. Immunol. 2017. 47: 800-805] make a detailed study of the transcription factor requirements of murine thymic NK cells. They provide a valuable insight into the distinctive identity of thymic NK cells with regard to Tbet, Nfil3, Id2, and Ets1. In addition, they clarify the nature of DX5 expression on NK cells and ILC-like cells in the murine thymus.