T-cell redeployment and intracellular cytokine expression following exercise: effects of exercise intensity and cytomegalovirus infection

The magnitude of lymphocytosis following exercise is directly related to exercise intensity. Infection with cytomegalovirus (CMV) also augments lymphocytosis after exercise. It is not known if the enhanced T-cell response to exercise due to CMV depends on exercise intensity. Furthermore, exercise-induced changes in T-cell expression of type I and type II cytokines are thought to be intensity dependent, but direct comparisons are lacking. The aim of this experiment was to determine if CMV affects the exercise-induced redistribution of T-cell subsets at varying intensities, and determine the effect of exercise intensity on CD8⁺ T-cell cytokine expression. Seventeen cyclists (nine CMV seropositive; CMV+) completed three 30 min cycling trials at −5, +5, and +15% of blood lactate threshold (LT). T-cell subsets in blood and intracellular expression of type I (IL-2, interferon(IFN)-γ) and type II (IL-4, IL-10) cytokines by CD8⁺ T cells pre, post, and 1-h post-exercise were assessed by flow cytometry. Independently of CMV, T-cell subset redistribution was greater after +15%LT compared to −5%LT (P < 0.05). Independently of intensity, CMV− mobilized more low- (CD27⁺ CD28⁺) and medium- (CD27⁺ CD28⁻) differentiated T cells than CMV+, whereas CMV+ mobilized more high (CD27⁻ CD28⁻) differentiated T cells. The numbers of IL-2+, IFN-γ+, IL-4+, and IL-10+ CD8⁺ T cells increased after exercise above LT. Only type I cytokine expression was influenced by exercise intensity (P < 0.05). In conclusion, T-cell redeployment by exercise is directly related to exercise intensity, as are changes in the number of CD8⁺ T-cells expressing type I cytokines. Although CMV+ mobilized more high-differentiated T cells than CMV−, this occurred at all intensities. Therefore, the augmenting effect of CMV on T-cell mobilization is independent of exercise intensity.