Mobilization of γδ T lymphocytes in response to psychological stress, exercise, and β-agonist infusion

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 (γδ) 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 β-agonist infusion on the mobilization of γδ T lymphocytes. Three separate studies compared lymphocytosis in response to an acute speech stress task (n = 29), high (85%Wmax) and low (35%Wmax) 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. γδ 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 β-agonist infusion. The mobilization of γδ 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 γδ T cells are stress-responsive lymphocytes which are mobilized during psychological stress, exercise, and β-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.