In addition to elevated levels of CD44, Tregs in IFNARflf/fl x Foxp3YFP-Cre mice also expressed higher percentages of other activation markers, including Ki-67+, ICOS+ and TIGIT+ (S1D and S1E Fig), consistent with an activated phenotype and greater degree of proliferation at day 5 post Armstrong infection. Here, TIGIT is linked to infection.