Characteristic of TIGIT and DNAM-1 Expression on Foxp3+ γδ T Cells in AML Patients

Foxp3+ γδ regulatory T (γδ Treg) cells promote tumor growth by various mechanisms and induce immuno-senescence. The novel immune checkpoint coinhibitory receptor T cell Ig and ITIM domain (TIGIT) shares similar ligands as the costimulatory receptor DNAX accessory molecule 1 (DNAM-1) and suppresses T cell responses in tumor patients. This study is aimed at characterizing whether the TIGIT/DNAM-1 axis is involved in the distribution and expression of Foxp3+ γδ Treg cell subsets in acute myeloid leukemia (AML) patients of different clinical statuses: de novo AML (27 patients), AML in nonremission (NR) (7 patients), and AML in complete remission (CR) (12 patients). Our data demonstrated that the proportions of Foxp3+, TIGIT+Foxp3+, and DNAM-1+Foxp3+ γδ T cells are significantly higher in de novo and NR patients. High levels of TIGIT and DNAM-1 on Foxp3+ γδ T cells correlated with increased Foxp3+ γδ T cell frequencies. In addition, a high TIGIT/DNAM-1 ratio was observed in de novo AML patients and healthy individuals (HIs). Furthermore, the phenotypic abnormalities in Foxp3+, TIGIT+Foxp3+, and DNAM-1+Foxp3+ γδ T cells were restored when the patients achieved CR after chemotherapy. Moreover, higher TIGIT+Foxp3+ γδ T cells were associated with AML patients who had poor overall survival and were an independent risk factor for prognosis. In conclusion, our study reveals for the first time that the TIGIT/DNAM-1 axis may be involved in Foxp3+ γδ Treg cells and indicates the clinical progression and prognosis of AML patients of different clinical statuses, which is considered beneficial for efficient AML immunotherapy.