Treatment of old mice with IL-2 corrects dysregulated IL-2 and IL-4 production

Splenic T cells from old BALB/c mice, activated in vitro withantibody to CD3e, secrete more IL-4 but less IL-2 than splenicT cells from young mice. The age-associated increase in IL-4secretion is associated with a significantly increased concentrationof intracellular IL-4 and its mRNA, although there is no increasein the number of activated T cells with intracellular IL-4.In contrast, the age-associated decrease in IL-2 secretion isassociated with a significant decrease in the number of activatedT cells with intracellular IL-2. In vivo there is a similarage-associated change in the number of activated T cells withdetectable cytokine. The number of activated T cells with intracellularIL-4 is comparable in old and young mice, while the number ofactivated T cells with intracellular IL-2 is significantly decreasedin old compared with young mice. Of great interest is the factthat old mice continuously exposed to IL-2 In vivo followingthe transplantation of J558 cells expressing the transfectedIL-2 gene product have an increased number of splenic T cellswith intracellular IL-2 that equals the level of such cellsobserved in young mice. Most important, the effect of continuousIL-2 administration in vitro was stable as spleen cells fromold, IL-2-treated mice when stimulated in vitro with anti-CD3ehad a young-like pattern of both intracellular IL-2 and IL-4expression as well as IL-2 and IL-4 secretion following in vitroactivation. Thus, it appears that exposure of old mice to exogenousIL-2 can redress the age-associated imbalance in cytokine expressionin vivo and cytokine secretion in vitro.