Eomes expression reports the progressive differentiation of IFN-γ-producing Th1-like γδ T cells

The transcription factor Eomesodermin (Eomes) plays a crucial role in regulating cytotoxic function, development, and survival of immune cells. γδ T cells can express Eomes, but its contribution to their differentiation is unknown. Using Eomes-IRES-GFP mice, we show that Eomes⁺ γδ T cells are unequally distributed among organs, with the highest proportion in spleen. While the majority of Eomes⁺ γδ T cells expressed Vγ1⁺ and Vγ4⁺ TCRs, Eomes was absent in Vγ5⁺ , Vγ6⁺ , and Vγ7⁺ subsets. Moreover, Eomes was co-expressed in γδ T cells with Th1 lineage-related factors such as CD27, T-bet, and Ly6C, but not with Th17 lineage-related genes. Eomes⁺ and Eomes^- γδ T-cell populations showed distinct gene expression profiles, with an increase of cytotoxic-related genes in Eomes⁺ γδ T cells. Furthermore, Eomes could be induced in peripheral γδ T cells by IL-12 and IL-4, and Eomes⁺ γδ T cells presented a higher proliferation rate and IFN-γ production when stimulated in vitro with IL-12 and IL-18. However, γδ T cells with very high Eomes levels displayed an exhausted phenotype with high levels of PD-1, and were less capable of IFN-γ production. Together, this study highlights Eomes as a marker for the differentiation of Th1-like effector γδ T cells.