MHC class II inhibits the generation of IL-17A+ Vγ6 γδ T cells in the thymus at perinatal stage

TCR γ chain loci of mice have seven variable (Vγ) gene segments (Vγ1, Vγ2, Vγ3, Vγ4, Vγ5, Vγ6, and Vγ7) using the Heilig and Tonegawa nomenclature. Vγ6+ γδ T cells, which develop in the thymus at the perinatal stage, are distributed within the mucosal tissues in the periphery. Vγ6+ γδ T cells are exclusive interleukin (IL)-17 producers among γδ T cells, and Vγ6+ IL-17A+ γδ T (γδT17) cells play important roles in protection against microbial infection and in the pathogenesis of inflammatory diseases, such as colitis and autoimmune diseases. We have previously reported that γδT17 cells develop from the CD4–CD8– (DN)2b stage in the thymus at the prenatal stage in a Bcl11b-dependent manner. However, details of the development of Vγ6+ γδT17 cells remain obscure. To analyze Vγ6+ γδ T cells in detail, we recently developed a monoclonal antibody (mAb; termed 1C10-1F7) specific to mouse Vg6 chain. Use of this mAb revealed that Vγ6+ γδ T cells in 0-day-old thymus were co-localized with medullary thymic epithelial cells (mTECs), which regulate T cell tolerance by self-antigen presentation using major histocompatibility complex (MHC) class II. Here, we report that MHC class II in the thymus inhibits the generation of Vγ6+ γδT17 cells. To assess differences in gene expression by Vγ6+ γδ T cells in the absence of MHC class II, we performed a microarray analysis and compared the transcriptome profiles of Vγ6+ γδT cells in the thymus of 0-day-old WT and MHC class II KO mice.