Ontogeny and localization of the cells produce IL-2 in healthy animals

► Naturally existing CD4 T cells that produce IL-2 were found in variety of tissues of healthy mice. ► Cells produced IL-2 are mostly CD4+, CD44+, CD62L+, and ICOS+. ► The frequency of cells produce IL-2 is highest in lamina propria. ► IL-2 produced cells are not detectable in newborn mice and become detectable 5 days after birth. ► A significant fraction of IL-2 produced cells co-produce IL-10 and IFN-γ.