NK-cell alloreactivity and the “mother donor effect.” (A-B) Transplantation from haploidentical NK-alloreactive donors improves EFS. (A) EFS in patients transplanted in CR from NK-alloreactive versus non–NK-alloreactive donors. (B) EFS in patients transplanted in relapse from NK-alloreactive versus non–NK-alloreactive donors. Reprinted from Ruggeri et al with permission.⁴¹  (C) EFS of patients receiving parental donor haploidentical HSCT for acute leukemia stratified by both donor sex and NK alloreactivity (NK-alloreactive mother donor transplantation, N = 21; NK nonalloreactive mother donor transplantation, N = 20; NK-alloreactive father donor transplantation, N = 19; NK nonalloreactive father donor transplantation, N = 40). Reprinted from Stern et al with permission.⁴⁴