Intensive exercise does not preferentially mobilize 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, which enables transmigration to the skin—are selectively mobilized in response to acute exercise. Methods Nine healthy men (mean ± SD age: 22.1 ± 3.4 yr) completed two exercise sessions: high-intensity continuous cycling (“continuous exercise” at 80% V˙O2max for 20 min) and low-volume high-intensity interval exercise (at 90% V˙O2max 10 × 1 min repetitions with 1 min recovery intervals). Blood was collected before, immediately and 30 min postexercise for cryopreservation 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 mobilized 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.