The age-related decline in interleukin-3 expression in mice.

Spleen lymphocytes form 5- to 37-month-old C57BL/6J mice were stimulated by concanavalin A (con A) in vitro, and the interleukin-3 (IL-3) expression was assessed by measuring the IL-3 activity in culture supernatants and the cytoplasmic IL-3 mRNA levels. The activity and mRNA level of IL-3 was maximum at 20 hr after culturing in the presence of con A. The IL-3 activity in the culture supernatants and the IL-3 mRNA level in lymphocytes declined 70% to 80% between 5 and 37 months of age. Northern blot analysis revealed no change in the size of IL-3 mRNA between young and old mice. When the expression of IL-3 and interleukin-2 (IL-2) by con A-stimulated lymphocytes was compared, both interleukins showed a similar declined with age.