PLZF Controls the Development of Fetal-Derived IL-17+Vγ6+ γδ T Cells

Expression of promyelocytic leukemia zinc finger (PLZF) protein directs the effector differentiation of invariant NKT (iNKT) cells and IL-4(+) gamma delta NKT cells. In this study, we show that PLZF is also required for the development and function of IL-17(+) gamma delta T cells. We observed that PLZF is expressed in fetal-derived invariant V gamma 5(+) and V gamma 6(+) gamma delta T cells, which secrete IFN-gamma and IL-17, respectively. PLZF deficiency specifically affected the effector differentiation of V gamma 6(+) cells, leading to reduced numbers of mature CD27(-)CD44(+) phenotype capable of secreting IL-17. Although PLZF was not required for V gamma 5(+) gamma delta T cells to develop, when these cells were reprogrammed into IL-17-secreting cells in Skint-1 mutant mice, they required PLZF for their effector maturation, similarly to V gamma 6(+) gamma delta T cells. The impaired effector differentiation of PLZF-deficient V gamma 6(+) gamma delta T cells was not due to increased apoptosis and it was related to reduced proliferation of immature CD27(+)CD44(-) V gamma 6(+) gamma delta T cells, which was required for their differentiation into mature CD27(-)CD44(+) IL-17-secreting cells. Thus, the present study identifies that PLZF function is not restricted to NKT or IL-4(+) T cells, but it also controls the development of IL-17(+) gamma delta T cells.