In human AML, IL21 mRNA was mostly expressed by CD4+ T cells (22 out of 32 patients analyzed) but not CD8+ T cells and CD34+ AML stem and progenitor cells (LSPCs) in the BM of newly diagnosed patients with AML (Figures 5A and S6A for LSPCs gating strategy). Here, IL21 is linked to acute myeloid leukemia.