IL2RA and leukemia: The expression of CD25 antigen, the α-chain of the interleukin-2 receptor (IL-2Rα), has been repeatedly shown to be associated with poor outcome in adults with either acute myelogenous (AML)1, 2, 3 or lymphoblastic leukemia.4, 5 To explain this finding mechanistically, it has been hypothesized that CD25+ AML blasts are enriched in chemoresistant leukemia stem cells (LSCs), as they bear an LSC-like molecular signature,2 are quiescent and can establish AML in xenograft models.6