IL15 and leukemia: Exercise and our injected dose of IL-15 in wild-type mice were suitable to transiently reach a peak of ∼100 pg mL−1 (∼0.76 × 10−11 m) in circulation, possibly low enough to avoid the negative consequences of chronically elevated IL-15 that may trigger leukemia (Fehniger et al., 2001) or pancreatic β-cell death (Chen et al., 2013) in mice.