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

Vα14 NKT cells express an invariant antigen receptor encoded by Vα14 and Jα281 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 β, pTα, and RAG1/2 but not Vα14 and surface CD3ɛ. Such pre-NKT cells were differentiated successfully in vitro into mature CD3ɛ(+) Vα14(+) NKT cells by IL-15 and granulocyte/macrophage colony-stimulating factor (GM-CSF) in conjunction with stroma cells. Interestingly, only GM-CSF without stroma cells induced the Vα14-Jα281 gene rearrangement in the pre-NKT cells. This also was confirmed by the findings that the number of mature Vα14 NKT cells and the frequency of Vα14-Jα281 rearrangements were decreased significantly in the mice lacking a GM-CSF receptor component, common β-chain. These results suggest a crucial role of GM-CSF in the development of Vα14 NKT cells in vivo.