TCF7 and infection: Indeed, long-term memory CD8+ T cells can derive from cells that previously expressed KLRG1.44 Adoptively transferred Tcf7 reporterlo cells can restore TCF-1 expression over 2 weeks.45 Our data indicate that the reversibility of Tcf7 repression during acute infection is limited, but not necessarily prevented, by Tcf7+22kb and Tcf7+17kb.