Protection against relapse and improved DFS on the basis of donor KIR B–content groups in AML. The AML cohort was evaluated for relapse (A) and DFS (B) on the basis of donor KIR B content by use of the indicated groups. On the basis of this analysis, donor KIR B–content groups are divided as: (1) “best” with a KIR B–content score of more than 2 where the KIR haplotype is Cen-B/B, Tel-x/x (defined as 2DL3 absent, 2DS2 and/or 2DL2 present); (2) “better” with a KIR B–content score of more than 2 and the KIR haplotype is Cen-A/x, Tel-B/x (defined as 2DL3 present, 2DS2 and/or 2DL2 present, 3DS1 and/or 2DS1 present or 2DL3 present, 2DS2 and/or 2DL2 absent, and 3DS1 and/or 2DS1 present); or (3) “neutral” with a KIR B–content score of 0 or 1 (defined as 2DL3 present, 2DS2 and/or 2DL2 absent, 3DL1 and 2DS4 present).