Abstract
The mobilization of cytotoxic lymphocytes, such Natural Killer (NK) cells and CD8(+) T cells, during stress and exercise is well documented in humans. However, humans have another cytotoxic lymphocyte subset that has not been studied in this context: the Gamma Delta (gamma delta) T lymphocyte. These cells play key roles in immune processes including the elimination of bacterial infection, wound repair and delayed-type hypersensitivity reactions. The current study investigated the effects of stress, exercise, and beta-agonist infusion on the mobilization of gamma delta T lymphocytes. Three separate studies compared lymphocytosis in response to an acute speech stress task (n = 29), high (85%W-max) and low (35%Wm(max)) intensity concentric exercise (n = 11), and isoproterenol infusion at 20 and 40 ng/kg/min (n = 12). Flow cytometric analysis was used to examine lymphocyte subsets. gamma delta T lymphocytes were mobilized in response to all three tasks in a dose-dependent manner; the extent of mobilization during the speech task correlated with concomitant cardiac activation, and was greater during higher intensity exercise and increased dose of beta-agonist infusion. The mobilization of gamma delta T lymphocytes was greater (in terms of % change from baseline) than that of CD8(+) T lymphocytes and less than NK cells. This study is the first to demonstrate that gamma delta T cells are stress-responsive lymphocytes which are mobilized during psychological stress, exercise, and beta-agonist infusion. The mobilization of these versatile cytotoxic cells may provide protection in the context of situations in which antigen exposure is more likely to occur. Crown Copyright (C) 2009 Published by Elsevier Inc. All rights reserved.