Because most of the patients in the current study were negative for CMV-DNA and CMV-IgM but positive for CMV-IgG,theNKG2Cpositivity of the abnormal NK cells from the patients with ANKL may have resulted from previous infection of CMV.Moreover, the expression of activating KIR isoforms associated with CMV infection in CLPD-NK[48] is different from the lack of KIR expression in ANKL and may help to identify the two diseases. This evidence concerns the gene CD40LG and aggressive NK-cell leukemia.