Polyfunctional capacity of T cell function in older adults

The precise polyfunctional capabilities of T cells from older persons are not well known. We determined the polyfunctionality of memory CD8+ and CD4+ T cell subsets using a 13-color flow cytometric assay that simultaneously analyzes IFN-gamma, TNF, MIP1-alpha, IL-2, and perforin expression after stimulation. PBMC from 37 older (mean age 82) and 30 younger (mean age 34) individuals were stimulated with a sub-maximal concentration of the mitogen SEB. Older adults were also assessed by the Fried frailty test. The proportion of highly polyfunctional cells that could perform 3, 4, or 5 functions was similar in the memory T cell subsets from older and younger individuals. The percentage of cells capable of performing each individual function had only small differences between the age groups. Within the older group however, polyfunctionality of central memory CD4+ and CD8+ T cells and CD8+ effector cells had in inverse correlation with frailty while not having a relationship with age. In conclusion, as a whole the frequency and polyfunctionality and mitogen-activated CD4+ and CD8+ memory T cell subsets in older individuals is preserved compared to the younger group. Therefore, the phenomenon of immunosenescence particularly in the non-frail elderly may not include the loss of capability and breadth of function of T cells if stimulated sufficiently. This may inform specific strategies to boost the older immune system.