KLRC1 and graft versus host disease: A prospective study evaluating EBV reactivation after CTLA4Ig-based haploidentical transplantation and its effect on GVHD revealed that the overall prevalence of EBV reactivation was 19 % in 71 patients, and a significant increase in chronic GVHD was observed after EBV reactivation (62.5 % vs. 8 %; p = 0.01), with a significant increase in and persistence of the NKG2A subpopulation of CD56 NK cells, whereas the NKG2C subpopulation decreased [126].