Most of the research conducted during the past twenty years has shown that a general decline in translation and transcription occurs with increasing age; however, essentially no information is currently available on the effect of age on the expression of specific genes. Although changes in gene expression are essential in mitogenesis, no information is now available on the role that gene expression might play in the well-documented, age-related decline in mitogenesis. Preliminary experiments conducted in the laboratories of the two Principal Investigators show that an age-related decline in total protein synthesis occurs in cultured lymphocytes. This decline is correlated with a decline in mitogenesis and interleukin-2 (IL2) production. The following hypothesis will be tested in the research described in this proposal: a decline in the expression of the gene for IL 2 by IL 2-producing T-cells is responsible for the age-related decline in IL 2 production by stimulated spleen lymphocytes. The genetic expression of IL 2 by 6- to 32-month-old Fischer F344 rats will be studied using spleen lymphocytes stimulated with concanavalin A. The absolute rates of IL 2 synthesis by limphocytes will be determined by measuring the rates of [3H]-valine incorporation into products that are immunoprecipitated by a monoclonal antibody to IL 2 and by measuring the specific activity of the valine precursor pool. The relative amounts of IL 2 mRNA in RNA isolated from lymphocytes will be quantified by dot hybridization with a cDNA probe to IL 2 mRNA. In addition, experiments will be conducted to establish that the age-related decline in IL 2 expression does not occur because of age-related changes in IL 1 production by macrophages or the number of IL 2-producing T-cells. Because IL 2 plays a critical role in mitogenesis and because the addition of exogenous IL 2 to lymphocyte cultures appears to reverse the age-related decline in mitogenesis, a knowledge of how aging affects the expression of IL 2 will be very important in our understanding of the age-related decline in the immune system. The long range objective of our research is to elucidate the role that gene expression plays in the aging process.
