In vivo, the DPP1-deficient NK cells and CTLs elicited during infection by the natural pathogen murine cytomegalovirus (MCMV) were indistinguishable from the wild-type cells but superior to those imparted by the CTL/NK cells of mice homozygous for null alleles of both GzmA and GzmB (GzmAB−/−) (Lopez et al., 2012). Here, CTSC is linked to infection.