Induction of differentiation of pre-NKT cells to mature Vα14 NKT cells by granulocyte macrophage colony-stimulating factor

V alpha 14 NKT cells express an invariant antigen receptor encoded by Va14 and J alpha 281 gene segments as well as natural killer (NK) markers, including NK1.1. Here, we describe a precursor population of NKT cells (pre-NKT) that expresses NK1.1, T cell antigen receptor beta, pT alpha, and RAG1/2 but not V alpha 14 and surface CD3 epsilon. Such pre-NKT cells were differentiated successfully in vitro into mature CD3 epsilon(+) V alpha 14(+) NKT tells by IL-15 and granulocyte/macrophage colony-stimulating factor (GR;I-CSF) in conjunction with stroma cells. Interestingly, only GM-CSF without stroma cells induced the V alpha 14-J alpha 281 gene rearrangement in the pre-NKT cells. This also was confirmed by the findings that the number of mature V alpha 14 NKT cells and the frequency of V alpha 14-J alpha 281 rearrangements were decreased significantly in the mice lacking a GM-CSF receptor component, common beta-chain. These results suggest a crucial role of GM-CSF in the development of V alpha 14 NKT cells in vivo.