When we analysed those genes differentially expressed in tissue-resident effector cells vs. tissue-resident memory cells (56), some of those genes preferentially expressed in resident effector IEL (“effector gene signature”), notably, Prdm1/Blimp1, Icos, and Gzmb were indeed more prominently expressed in Rgs1-/- OT-I IEL, isolated on day 8 post-infection with Lm-OVA (data not shown). Here, ICOS is linked to infection.