Donor KIR B gene content score affects outcome. Relapse (A) and disease-free survival (B) of patients with AML after receiving transplants from donors with different KIR genotypes. Donors with a KIR B gene content score of 0 or 1 conferred less protection from relapse and lower disease-free survival compared with donors with a score of 2 or higher and a KIR haplotype Cen-A/x and Tel-B/x haplotype. Donors with a KIR B gene content score of 2 or higher and homozygous for Cen-B (Cen-B/B) conferred the best protection from relapse and highest DFS. For a detailed description, see Figure 4 in Cooley et al.¹