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Apoptosis of T-Cell Subsets after Acute High-Intensity Interval Exercise.

INTRODUCTION
High-intensity interval training (HIT) exercise has gained much interest in both performance and recreational sports. This study aims to compare the effect of HIT versus continuous (CONT) exercise with regard to changes of circulating T cells and progenitor cells.


METHODS
Subjects (n = 23) completed an HIT test and an isocaloric CONT test. Blood samples were collected before, immediately after, and 3 and 24 h postexercise for the assessment of low differentiated (CD3CD28CD57), highly differentiated T cells (CD3CD28CD57), regulatory T cells (Tregs) (CD4CD25CD127), hematopoietic progenitor cells (CD45CD34), and endothelial progenitor cells (CD45CD34KDR) by flow cytometry. The detection of apoptosis was performed by using labeling with annexin V. To analyze potential mechanisms affecting T cells, several hormones and metabolites were analyzed.


RESULTS
Both exercise tests induced an increase of catecholamines, cortisol, and thiobarbituric acid-reactive substances (P < 0.05). CONT induced a higher increase of apoptosis in low differentiated T cells compared with the HIT (CONT: 3.66% ± 0.21% to 6.48% ± 0.29%, P < 0.05; HIT: 3.43% ± 0.31% to 4.71% ± 0.33%), whereas HIT was followed by a higher rate of apoptotic highly differentiated T cells (CONT: 21.45% ± 1.23% to 25.32% ± 1.67%; HIT: 22.45% ± 1.37% to 27.12% ± 1.76%, P < 0.05). Regarding Tregs, HIT induced a mobilization, whereas CONT induced apoptosis in these cells (P < 0.05). The mobilization of progenitor cells did not differ between the exercise protocols.


CONCLUSION
These results suggest that HIT deletes mainly highly differentiated T cells known to affect immunity to control latent infections. By contrast, CONT deletes mainly low differentiated T cells and Tregs, which might affect defense against new infectious agents.