IL-9 secretion by LSCs leads to Th1 polarization of bone marrow–infiltrating CD4⁺ T cells, which in turn stimulates the proliferation of LSCs in patients with AML. In the bone marrow of patients with AML, LSCs secrete IL-9, which skews the Th-cell profile of infiltrating CD4⁺ T cells toward a Th1 response. These polarized Th1 cells secrete INF-γ and stimulate the proliferation of AML LSCs in the bone marrow, which could contribute to disease progression. IFN-γ, interferon-γ. The figure was created with BioRender.com.