In a phase III clinical trial (n=320), immunotherapy with histamine dihydrochloride (HDC) and interleukin-2 (IL-2) was found to prevent relapse in the post-consolidation phase of AML.12 13 Further studies have pinpointed that aspects of NK cell function impact favorably on the outcome of AML patients receiving HDC/IL-2.14–18. Here, IL2 is linked to acute myeloid leukemia.