What is the central question of the study? Are CD31 angiogenic T (T ) cells preferentially mobilized in response to acute exercise? What is the main finding and its importance? Our study reveals that T cells are redistributed into the circulation in response to acute strenuous exercise, but to a lesser extent than CD31 T cells. Of the T cells mobilized, T cells expressing CXCR4 show greater redistribution compared with CXCR4 T cells. Stromal-derived factor 1-α does not appear to play a role in the redistribution of T cells expressing CXCR4. The results suggest that a single bout of strenuous exercise might provide a short vasculogenic window, which could benefit the vascular system by redistributing CD31 T cells. CD31 T cells have been documented to possess vasculogenic properties and have been termed 'angiogenic T cells' (T cells). No study to date has fully characterized the effect of acute exercise on T cells. Twelve male participants aged 24-45 years undertook a running 10 km time trial, with peripheral blood samples taken before, immediately after and 1 h postexercise for quantification of T cells and subsequent CXCR4 cell surface expression by flow cytometry. The T cells demonstrated a 102% increase in number in the peripheral circulation immediately postexercise compared with pre-exercise levels, followed by a large egress (50%) from the circulation in total T cells 1 h postexercise. This was due to changes in both CD4 and CD8 T cells, with CD8 T cells displaying greater ingress (123%) and egress (52%) compared with CD4 T cells (ingress, 83%; egress, 37%). The cell surface expression intensity of CXCR4 was affected only on CD8 T cells, with a significant increase in cell surface expression immediately postexercise versus pre-exercise levels. The CD31 T cells displayed greater redistribution than CD31 T cells (119 versus 102%). CXCR4-expressing T cells showed greater response to acute exercise than CXCR4 cells, which was accompanied by large changes in CXCR4 ligand SDF-1α. The results show that acute exercise increases T cells in the circulation in response to an acute exercise stressor. Additionally, CXCR4 cell surface expression appears to be increased in response to exercise, which may result from the direct upregulation of CXCR4 on the T-cell surface or could be due to CD31 T cells being redistributed into the blood expressing greater levels of CXCR4.

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