Preliminary evidence of reductive stress in human cytotoxic T-cells following exercise

This study investigated immunophenotypic differences in intracellular thiol redox state of peripheral blood mononuclear cells (PBMCs) isolated from trained (TR, n=9, mean {plus minus} SD: age 28 {plus minus} 5 years; BMI 23.2 {plus minus} 2.6 kg·m2; VO2max 56.9 {plus minus} 6.1 ml·kg-1·min-1) and recreationally active (RA, n=11, mean {plus minus} SD: age 27 {plus minus} 6 years; BMI 24.2 {plus minus} 3.7 kg·m2; VO2max 45.1 {plus minus} 6.4 ml·kg-1·min-1) participants before and after a maximal aerobic exercise tolerance test. Blood samples were taken before (PRE), during (sample acquired at 70% HRmax), immediately (POST+0) and 15 minutes post-exercise (POST+15). PBMCs were isolated and reduced thiol analysis (fluorescein-5 maleimide (F5M)) by immunophenotype (CD3+, CD4+ and CD8+) was performed using flow cytometry. A significant increase in cellular F5M fluorescence was observed in CD3+ T-cells at POST+0, with changes driven to a greater extent by CD8+ T-cells (fold change in both groups CD4: +2.3, CD8: +2.8; p<0.05). Further analysis revealed a population of highly reduced CD8+ T-cells (CD8+T-reduced+) that significantly increased from PRE to POST+0 in RA participants only (RA: +272 cell/µL, p<0.05). To further understand these results, CD8+T-reduced+ and CD8+T-reduced- cells were analysed for immunophenotype in response to the same exercise protocol (n=6, mean {plus minus} SD: age 24 {plus minus} 5 years; BMI 25.7 {plus minus} 4.1 kg·m-2; VO2max 41.33 {plus minus} 7.63 ml·kg-1·min-1). CD8+T-reduced+ had significantly less lymphoid homing potential (CCR7) POST+0 compared to PRE. This study is the first to demonstrate that lymphocyte populations become more reductive in response to acute exercise.