Low cardiorespiratory fitness is associated with higher differentiation of CD8pos T-cells but not NK-cells in the elderly: Preliminary evidence from the Texas City Stress and Health Study

Abstract

Aging and latent cytomegalovirus (CMV) infection drives NK-cell and T-cell differentiation, but the effect of cardiorespiratory fitness (VO2max) on this process is unknown. We measured NK-cell (NKG2C/CD57) and T-cell phenotypes (CD28/CD27) by flow cytometry in relation to age, CMV infection, and VO2max in 317 respondents of the Texas City Stress and Health Study (58.4% female) aged 25–91 years. VO2max was estimated using non-exercise equations that incorporate physical activity rating, body-mass index, age and sex. VO2max was associated with the proportions of ‘early’ (CD28pos/CD27pos) and ‘late’ (CD28neg/CD27neg) differentiated CD8pos T-cells in 65plus year olds, but not in those under 65 years. The effect was independent of CMV serostatus and driven by a higher proportion of ‘early’ and lower proportion of ‘late’ differentiated CD8pos T-cells within the middle VO2max tertile compared to those in the lower tertile. There was no effect of VO2max on the proportion of NKG2Cpos, CD57pos or NKG2Cpos/CD57pos NK-cells. There was an age-independent increase in the proportion of ‘late’ and decreased proportion of ‘early’ CD8pos T-cells in CMV-seropositive individuals. CMV seropositivity was also associated with an age-independent increase in the proportion of NKG2Cpos/CD57pos NK-cells. Overall, low cardiorespiratory fitness shifts CD8pos T-cells toward a ‘late’ differentiated phenotype in the elderly that is independent of CMV serostatus, but does not affect NK-cell phenotype. These findings highlight the potential benefits of exercise on the aging immune system.