IL2 and infection: These memory cells include Th1- and Tfh-like subsets (which may represent T effector memory cells; Marshall et al., 2011; Pepper et al., 2011; Hale et al., 2013), tissue resident memory cells that provide rapid protection at frontline sites of infection (Iijima and Iwasaki, 2014; Schreiner and King, 2018), and a less differentiated T central memory (Tcm) cell population that displays an increased capacity to proliferate and produce IL-2 upon secondary challenge (Pepper and Jenkins, 2011).