CD44 and infection: In contrast to the loss of memory/effector Tregs observed in WT mice by Srivastava et al. (2014), we observed an enhanced percentage of memory/effector Treg as defined by CD44 expression on days 5, 7 and 14 post-infection in IFNARfl/fl x Foxp3YFP-Cre mice, as well as higher levels of expression of Ki-67, ICOS and TIGIT.