Interleukin-2 production in the neonatal mouse.

Neonatal mouse spleen and thymus cells fail to produce interleukin-2 (IL-2) in vitro. In vitro IL-2 production by spleen cells begins to develop between 20 and 27 days of age and reaches adult levels at 40 days of age. Thymus cells do not develop the ability to produce IL-2 in vitro. Addition of neonatal spleen, neonatal thymus, or adult thymus cells to adult spleen cell cultures inhibits IL-2 production. Treatment of the added cells with mitomycin does not abrogate their suppressor activity. Soluble factors, obtained from three-day cell cultures of neonatal spleen, neonatal thymus, or adult thymus also suppress IL-2 production in adult spleen cell cultures. Addition of interleukin-1 raises IL-2 production in adult thymus, neonatal spleen, or neonatal thymus cell cultures slightly, but the IL-2 productivity is still considerably lower than that of adult spleen in the absence of IL-1. The results indicate that suppressor cells for IL-2 production are present in neonatal spleen and thymus. The splenic suppressor cell activity disappears after birth, but thymic suppressor cell activity is retained into adulthood.