During intrathymic development, γδ T cells emerge before αβ T cells at the early stages, and in vivo, most mature γδ T cells home toward mucosal and epithelial tissues, in which γδ T cells play unique roles in first-line responses to infection and tumor immune surveillance via direct cytotoxicity and the secretion of cytokines, such as IFN-γ and IL-17 [1, 8, 30]. The gene discussed is IL17A; the disease is infection.