Back to the future--defining NK cells and T cells.

In this issue of the European Journal of Immunology (EJI), Stewart et al. report about a population of gammadelta-T cells expressing an extensive repertoire of NK cell receptors, and the presence of non-rearranged germline TCRdelta transcripts in conventional NK cells. These findings and other recent studies highlight the similarities of NK cells and T cells and the problems in discriminating between these two lineages.