It is well documented that the production of interleukin 2 (IL-2) by lymphocytes declines with increasing age. Using a cDNA probe to IL-2, the effect of age on the expression of IL-2 mRNA was studied on concanavalin A-stimulated lymphocytes. The induction of IL-2 mRNA by concanavalin A was maximum after 20 hr of incubation. Northern blots demonstrated that the cDNA probe to IL-2 hybridized to an 11 S to 12 S RNA species. No age-related change in the size of the IL-2 mRNA was observed. In addition, there was no evidence of an age-related change in IL-2 mRNA degradation or the post-transcriptional processing of IL-2 mRNA. The induction of IL-2 mRNA decreased 85% between 5 and 29 months and paralleled the decline in IL-2 production and lymphocyte proliferation. Therefore, the age-related decline in the ability of lymphocyte population to produce IL-2 arises from a decrease in the ability of the lymphocytes to genetically express IL-2 mRNA.
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