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 (CD56 "regulatory" and CD56 "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 CD56 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.