Intensive exercise does not preferentially mobilise skin-homing T cells and NK cells

Purpose: This study investigated whether natural killer (NK) cells and CD8+ T cells expressing cutaneous lymphocyte antigen (CLA) – a homing molecule for endothelial cell leukocyte adhesion molecule 1 (ELAM-1), which enables transmigration to the skin – are selectively mobilised in response to acute exercise.

Methods: Nine healthy males (mean ± SD age: 22.1 ± 3.4 years) completed two exercise sessions: high-intensity continuous cycling (‘continuous exercise’ at 80% MAX for 20 min) and low-volume high-intensity interval exercise (‘HIIE’ at 90% MAX 10 × 1 min repetitions with 1 min recovery intervals). Blood was collected before, immediately- and 30 min post-exercise for cryo-preservation of peripheral blood mononuclear cells. CLA+ and CLA− cells were quantified within NK subpopulations (CD56bright ‘regulatory’ and CD56dim ‘cytotoxic’ cells) as well as the following CD8+ T cell subpopulations: naive (‘NA’; CD45RA+CCR7+), central memory (‘CM’; CD45RA−CCR7+), effector-memory (‘EM’; CD45RA−CCR7−) and CD45RA-expressing effector-memory cells (‘EMRA’; CD45RA+CCR7−).

Results: CLA+ NK cells and CD8+ memory T cells increased in response to both exercise bouts, but, overall, their numerical contribution to the exercise lymphocytosis was inferior to CLA− cells, which increased to a much greater extent during exercise. Tellingly, the most exercise-responsive cells – effector memory CD8+ cells and CD56dim cells – were CLA−.

Conclusions: A small subset of CLA+ lymphocytes are mobilised into blood during acute intensive exercise, but CLA+ cells are not major contributors to exercise lymphocytosis, thus providing preliminary evidence that the skin is not a major origin, or homing-destination, of exercise-sensitive lymphocytes.