Defense-oriented inflammatory reactivity supports survival at younger age, but might contribute to health impairments in modern, aging societies. The IL-1 cytokines are highly conserved and regulated, pleiotropic mediators of inflammation, essential to respond adequately to infection and tissue damage, but also with potential host damaging effects when left unresolved. In this review, we discuss how continuous low-level IL-1 signaling contributes to aging-associated hematopoietic stem …