AGE-RELATED-CHANGES OF CYTOKINE PRODUCTION BY MURINE HELPER T-CELL SUBPOPULATIONS

Mouse CD4+ T cells were subdivided into two subsets by cell surface ma rkers: CD44(lo)CD45RB(hi) (naive) and CD44(hi)CD45RB(lo) (memory)T cel ls. We have reported that CD44(lo)CD45RB(hi) T cells, which are predom inant in young mice, decreased with age, while CD44(hi)CD45RB(lo) T ce lls increased. Among T cells of the same phenotype, however, it remain s to be solved whether or not there is a functional difference between young and old. Therefore, we compared old with young T cells by a cyt okine production assay (IL-2, IFN-gamma, IL-4 and IL-10). We employed the negative selection method by cell affinity column instead of flow cytometry as it was important to use T cells not reacted with antibodi es in the cytokine production assay and as the method is quick enough to preserve the viability of the cells. Then the divided T cells were stimulated with immobilized anti-CD3 epsilon monoclonal antibody (mAb) . Young CD4+ T cells produced more IL-2 and IL-4 than aged CD4+ T cell s, while aged CD4+ T cells produced more IL-10 than young cells. There was no distinct age-related change in IFN-gamma production. As concer ns purified CD4+ T cell subpopulations, young CD44(lo)CD45RB(hi) T cel ls produced more IL-2 (5.3-fold higher) than young CD44(hi)CD45RB(lo) T cells and much more IL-2 (>10-fold higher) than both groups of aged T cells, Dramatic IFN-gamma production was found in young and old CD44 (hi)CD45RB(lo) T cells and young CD44(lo)CD45RB(hi) T cells; however, IFN-gamma production of old CD44(lo)CD45RB(hi) T cells was much lower (1/16-1/20) than that of other cell groups. IL-4 production was mainly observed in the CD44(hi)CD45RB(lo) T cell group in both young and old mice, although the former produced more IL-4 (5.2-fold higher) than t he latter. There was no remarkable difference between young and old mi ce in the pattern of IL-10 production. These phenomena could reveal fu nctional heterogeneity of aged CD4+ T cell subpopulations under natura l conditions. Even if the surface marker is the same, the pattern of c ytokine production is different between young and old cells.