KLRC2 and graft versus host disease: Thus, the assessment of KIRneg NK cells’ frequencies can be implemented, together with other NK cell properties, including the NKG2C genotype (22), KIR genotype, and alloreactivity (23, 24), for the screening of patient relatives to select optimal donors whose graft helps to prevent post-transplant HCMV-I/R and to ameliorate the clinical outcome of recipients in terms of engraftment, fast immune-reconstitution, and prevention of disease relapse and GvHD onset.