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) over dotO(2max) for 20 min) and low-volume high-intensity interval exercise (at 90% (V) over dotO(2max) 10 x 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 (CD56 bright regulatory'' and CD56(dim) cytotoxic'' cells) as well as the following CD8+ +/- 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 +/- 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 CD56(dim) 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.