IFN-g-producing and IL-17-producing GD T cells differentiate at distinct developmental stages in murine fetal thymus

gd T cells develop at the double-negative (DN) 2 and DN3 stages and acquire functions to produce IL-17 and IFN-g in fetal thymus. However, the relationship between differentiation stages and their functions was unclear. In this study, we found that, although IFN-g-producing and IL-17-producing gd T cells developed from DN2 cells, only IFN-g-producing gd T cells developed from DN3 cells, indicating the direct generation of IL-17-producing gd T cells from the DN2 stage, not through the DN3 stage. Single-cell analysis revealed that DN2 cells contained heterogeneous gd T cell precursors with or without an ability to develop IL- 17 producers. Inactivation of B cell leukemia/lymphoma 11b, a zinc finger transcription factor responsible for transition from early to late stages of DN2 cells, completely abrogated the development of IL-17-producing gd T cells, although a unique subset of IFN-g-producing gd T cells expressing a high level of promyelocytic leukemia zinc finger was able to develop. Thus, our results reveal that gd T cells are functionally differentiated to IFN-g and IL-17 producers at different developmental stages in fetal thymus.