T Before NK

Abstract
Natural killer T (NKT) cells are a small subset of T lymphocytes that express both activating T cell receptors and inhibitory NK cell receptors. In a Perspective, [MacDonald][1] discusses intriguing new findings published here ([ Benlagha et al .][2]) and elsewhere, that identify an early NKT cell precursor in the thymus that expresses the T cell receptor but not NK cell receptors, yet can give rise to NKT cells that express both. [1]: http://www.sciencemag.org/cgi/content/full/296/5567/481 [2]: http://www.sciencemag.org/cgi/content/short/296/5567/553