Functional characterisation of CD8(+) T cells mobilised with acute supramaximal high-intensity interval exercise: implications for immune surveillance.

OBJECTIVES: The beneficial influence of exercise on outcomes such as infection control and cancer prevention has been attributed partly to the immune system response during physical exertion. CD8(+) T cells play a crucial role in immune surveillance, and in this study, we performed an in-depth analysis of the impact of supramaximal high-intensity exercise (HIIT) on CD8(+) T-cell dynamics and function, which are currently lacking in the literature. METHODS: CD8(+) T cells obtained from healthy human subjects before and after 3 × 30 s of HIIT were analysed ex vivo for viability and expansion properties, metabolic function using SeaHorse, IFN-gamma release using EliSpot, phenotype using RNA-seq and flow cytometry, and cytotoxic capacity by co-culture with HEK293T cells. RESULTS: Exercise led to a threefold increase in CD8(+) T-cell count, and CD8(+) T cells obtained after exercise had a more cytotoxic profile. Post-exercise CD8(+) T cells had a lower glycolytic capacity than pre-exercise cells, and incubation of pre-exercise CD8(+) T cells with post-exercise serum replicated this metabolic shift, suggesting a systemic effect of exercise on CD8(+) T-cell metabolism. Importantly, CD8(+) T cells maintained their viability and expansion properties despite the metabolic challenges induced by exercise. Functionally, post-exercise CD8(+) T cells showed increased release of IFN-gamma and an enhanced unspecific cell killing capacity as demonstrated by co-culture with the immortalised cell line HEK293T. CONCLUSION: The pronounced increase in the total number of circulating CD8(+) T-cells with an increased cytotoxic capacity suggests a potential improvement in immune surveillance after acute HIIT.