Aerobic training increases the stimulated percentage of CD4+CD25+ in older men but not older women

The purpose of the present study was to determine whether 12 months of moderate intensity cycling would increase the expression of IL-2 (CD25⁺) receptors in T helper (CD4⁺) lymphocytes in men and women aged 65–75 years. Fourteen men and 10 women completed 52 weeks of moderate intensity cycling (60% VO₂peak). Subjects trained (TR) three times per week for 45 min per session. Eight age-matched untrained (UT) male and eight UT female subjects acted as controls. Resting blood samples were taken from TR and UT subjects every 4 weeks. Leukocyte concentration was measured using a full blood count. PHA-stimulated CD4⁺ lymphocytes were analysed for changes in the expression of CD25⁺, by flow cytometry. Training significantly increased VO_2peak (l min⁻¹, ml kg⁻¹ min⁻¹) in male (+14.3, +16%) and female (+16.7, +27.8%) groups. The TR male group showed a significantly lower percentage of CD4⁺CD25⁺ than the male UT in January but the TR male percentage was significantly higher than the UT male group during February, March, April, May, June, September B and December. The female TR group showed a significantly higher percentage CD4⁺CD25⁺ than the female UT only during July. There were also significant sequential monthly changes in the percentage of CD4⁺CD25⁺ for male and female UT and TR groups. Significant increases in the percentage of CD4⁺CD25⁺ in the male TR group suggest training-enhanced lymphocyte mitogenic responsiveness. Moderate intensity long-term training may increase the recruitment of active memory CD4⁺CD25⁺ in men rather than women.