Progressive decrease of CD8high+ CD28+ CD57- cells with ageing.

An age-dependent decrease in T cell responsiveness to CD28 costimulation has been described. In order to test the hypothesis that an age-related decrease in CD28 expression by CD8+ T lymphocytes might be involved, we analysed 67 healthy donors ranging in age from 15 to 69 years for their CD8+ T cell expression of CD28 and CD57. We found a statistically significant decrease of CD28 expression through ageing and a significant increase of CD57 expression, both markers being mutually exclusive. Given that cytomegalovirus (CMV) is reported to induce CD57 expression, and since the carrier status for this ubiquitous virus increases with age in the general population, it seemed essential to evaluate whether the phenotypic age-related changes described in CD8high+ cells were not influenced by the CMV carrier status of the individuals. Accordingly, we performed a multivariate analysis to assess the independent association of age and CMV carrier status with CD28 and CD57 expression in CD8high+ cells. Results showed that the progressive decrease in CD8high+ CD28+ CD57- cells was associated only with age, while the expansion of the CD8high+ CD28- CD57+ subset depended both on age and CMV, although mainly on age. We conclude that ageing is accompanied by a progressive loss of CD28 expression in CD8+ T cells and a reciprocal enhancement of CD57 expression, both facts being probably related to the repeated antigenic stimulation occurring throughout life.