Expression of TIGIT on Treg and the Treg suppressor function. (A) TIGIT delineates human rTreg and aTreg. (B) Naive proliferation at day 4 in the absence of Treg. (C) TIGIT expression on Treg and Naive (top and middle panel) was analyzed at day 4 during a suppressor assay (bottom panel). (D) Suppression by different Treg subsets presented as percent inhibition of Naive proliferation. Data are presented as mean + standard deviation of 3 donors. (E) Naive, TIGIT^hi rTreg, and TIGIT^lo rTreg activated in vitro with plate-bound anti-CD3 (3 μg/mL) and soluble anti-CD28 (1 μg/mL) antibodies and IL-2 (200 U/mL) for 3 days. Cells were supplemented with IL-2 at day 4 and analyzed for FOXP3 and IFN-γ production by intracellular staining at day 6. Data are representative of results from 3 individuals.