The age-dependent cytokine production by murine CD8+ T cells as determined by four-color flow cytometry analysis

Flow cytometry has been used to simultaneously examine intracellular cytokine production and expression of CD44 and CD45RB by murine CD8+ T cells derived from young (2-3 months) or aged (18-22 months) mice. Cytokine production by aged CD8+ T cells differs from that by CD8+ T cells derived from young animals in that a significantly higher percentage of the aged can be triggered to produce interleukin (IL)-4, interferon (IFN)-gamma, and tumor necrosis factor alpha (TNF alpha). Conversely, a greater fraction of young CD8+ T cells produce IL-2. Aged mice not only have a higher percentage of CD8+/CD44hi T cells, but also a larger fraction of these cells are IFN-gamma+ and IL-4+, while a lower fraction are IL-2+ than is observed in young CD8+/CD44hi T cells. In terms of relative contribution to total cytokine synthesis, a greater fraction of CD8+ T cells produce IFN-gamma and IL-4 than in CD4+ T cells, whereas CD4+ T cells are the major producers of IL-2.