Selective depletion of interleukin-10-expressing (IL-10+) Treg cells promoted tumor growth by lifting the restraint on IL-17 production from effector CD4<sup>+</sup> T cells, thereby directly stimulating tumor cell proliferation; depletion of IL-10<sup>-</sup> Treg cells led to pronounced tumor regression. The gene discussed is IL10; the disease is neoplasm.