Altered expression of various receptors on T cells in young and old mice after mitogenic stimulation: a flow...

To understand mechanism underlying the age-related impairment of T cell functions, changes in the expression of cell surface receptors were examined in T cells after mitogenic stimulation by flow cytometry and results were compared between young and old mice. Before stimulation, no significant difference was observed in the density of TCR alpha beta, CD3, CD122 (IL-2R beta), IL-2R gamma, CD28 and CD95 (Fas) of T cells between young and old mice. As for CD25(IL-2R alpha) and CTLA-4, relative intensity and percentage of positive cells were higher in old than in young mice, although the levels were low compared with those after stimulation. After mitogenic stimulation, increased expression of the density was observed in CD25, IL-2R beta, IL-2R gamma, CD28, CTLA-4 and CD95 and the magnitude of increase was more pronounced in T cells from young than those from old mice. The expression of TCR alpha beta and CD3 decreased after mitogenic stimulation, and the degree of expression quickly recovered to the initial level in young mice, but not in old mice. Lower expression of TCR, IL-2 receptors and co-stimulatory molecules in T cells from old mice could be responsible for the impaired proliferation after mitogenic stimulation.