IL7R and infection: Unfortunately, this strategy does not work for CD4 T cells [74], but we have recently identified CD4 memory precursor effector (MPEC) T cells early in infection using the transient downregulation of CD127 on cells that have not yet changed other markers of activation to mark a subset of cells that differentiate into the memory lineage (M.M.O., Victor H. Carpio, Brian E. Dillon, R.S., unpublished data).