Age‐associated increase in the expression of T cell antigen receptor γ chain genes in mice

T cell function generally declines with age. To determine the underlying cause of the age‐related decline, we compared the expression levels of T cell antigen receptor genes encoding γ, β and α chains in the lymphoid tissues of young (8 wk old) vs. aged (40 wk old) mice. An age‐associated increase in γ chain gene transcripts was evident in the thymocytes, spleen cells and mesenteric lymph node cells. Aged mice had a relatively high proportion of CD3⁺CD4⁻CD8⁻ cells but a reduced level of CD3⁺CD4⁻CD8⁺ cells in the lymphoid tissues, as compared with young counterparts. The allo‐reactivity in the lymphoid cells, as assessed by mixed lymphocyte reaction (MLR) responses, decreased with advancing age. On the contrary, increased levels of syngeneic MLR and spontaneous cytolytic activity were noted in the lymphoid cells of aged mice, as compared with findings in their young counterparts. A remarkable increase in the number of CD3⁺CD4⁻CD8⁻ cells and level of the γ chain gene messages was also detected in the responder cells of day 4 syngeneic MLR culture from aged mice. An increase in the number of T cells bearing γ chain may be related to the alterations in immunological functions in aged mice.