To be or not to be a pro-T?

Recent studies have begun to unravel some of the molecular pathways that ap pear to control the processes of T cell determination in the earliest thymo cyte precursors. In addition, the analyses of mouse mutants with an entirel y alymphoid thymus have shed light on the developmental relationship of pro -T cells and thymic dendritic cells, revealing that development of thymocyt es and thymic dendritic cells can be dissociated.