Ageing-associated changes in cellular immunity based on the SENIEUR protocol

To investigate ageing-associated changes in cellular immunity, we recruited three groups of healthy subjects based on SENIEUR protocol criteria. In addition, 10 subjects were randomly selected from each group to isolate their T cells from peripheral blood mononuclear cells; T cell proliferation after phytohemagglutinin (PHA) stimulation was determined by methyl thiazolyl tetrazolium assays. There were no marked differences in the absolute numbers of peripheral blood T cells, NK cells or B cells among the three groups (P > 0.05). Also, no significant differences were noted in the numbers of CD4+ cells, CD8+ cells, or the CD4+/CD8+ ratios (P > 0.05). After PHA stimulation, T cell proliferation was markedly increased, with the highest level in group C and the lowest level in group A (P < 0.05). Cytokine-induced killer tumouricidal activities were also dramatically increased, with the highest activity in group C and the lowest activity in group A (P < 0.05). Our findings suggest that the number of immune cells remains unchanged with advanced age. However, there is a trend for decreased cellular immunity with an increase in age.