Goodier et al. reported that in a Gambian population with a high frequency of HCMV infection, children reached the percentage of terminally differentiated NK cells (CD56dim/CD57+/NKG2C+) of an adult (nearly 70%) by the age of six, while Europeans barely reached these numbers in adulthood (nearly 50%) (26). This evidence concerns the gene KLRC2 and cytomegalovirus infection.