The effect of taurine on the age-related decline of the immune response in mice: the restorative effect on the T cell proliferative response to costimulation with ionomycin and phorbol myristate acetate.

1. Proliferative responses to the costimulation with phorbol-12-myristate-13-acetate (PMA) and suboptimal doses of ionomycin in the purified T and B cells from old mice were lower than those from young mice. 2. The degree of the age-related decline was more significant in T cells than in B cells. 3. Taurine, a sulfur containing amino acid, augmented the proliferative responses of T cells from both young and old mice. 4. The augmentation of the proliferative response by taurine was more marked in old T cells than in young T cells. 5. The concentration of intracellular free calcium ion ([Ca2+]i) was significantly lower in old T cells when stimulated with PMA and ionomycin than observed in young T cells. 6. In the presence of taurine, the concentration of [Ca2+]i in the old T cells significantly increased under stimulation by PMA and ionomycin. 7. The results indicate that taurine improved the proliferative response in old T cells by restoration of the increment of the concentration of [Ca2+]i under the stimulation by PMA and ionomycin.