Redeployment Of Immune Cell Subsets Across Multiple Exercise Intensities In The Context Of Cytomegalovirus Infection

Abstract

The immune response to acute exercise is directly related to exercise intensity, with a greater number of leukocytes mobilized by higher intensities. Within leukocytes, antigen experienced cells with effector functions are more exercise responsive. We have previously shown that factors driving accumulation of these high differentiated cells, including cytomegalovirus infection (CMV +), are associated with greater leukocyte redeployment after exercise. It is not known if the differences in the immune response to exercise between CMV+ and CMV- individuals depends on exercise intensity. PURPOSE: To determine if CMV infection affects T cell and monocyte redeployment across multiple exercise intensities. METHODS: 17 cyclists (9 CMV+; Mean ± SD: Age: 31 ± 5 yrs, BMI: 23.1 ± 1.9 kg/m2) completed three 30min cycling trials at -5, +5, and +15% of blood lactate threshold (LT). Monocyte and T cell subsets present in the blood pre-, post-, and 1h post-exercise were enumerated using flow cytometry. Cytokine expression by T cell subsets was also characterized. The impact of CMV and intensity on exercise-induced changes in cell subsets was analyzed with linear mixed models. RESULTS: CD14hiCD16-monocytes, low differentiated (CD27+CD28+, CD27+CD28-, CD45RA+CD62L+, CD45RA-CD62L+), and high differentiated (CD45RA-CD62L-) CD4+ T cells were mobilized to a greater extent by exercise above LT compared to -5%LT. Mobilization of low differentiated (CD27+CD28+, CD27+CD28-, CD45RA+CD62L+, CD45RA-CD62L+) and high differentiated (CD45RA-CD62L-, CD45RA+CD62L-) CD8+ T cells was significantly greater with +15%LT than -5% and +5% LT. All cells returned to pre-exercise numbers by 1h post-exercise. Larger increases in the number of CD8+T-cells expressing IL-6, IL-10, and IFN-γ were observed after +15% than -5%LT. CMV+ subjects mobilized a greater number of high differentiated CD4+ and CD8+ T cells than CMV- at all intensities. CONCLUSIONS: The mobilization of monocyte and T cell subsets by exercise was directly related to exercise intensity, as were exercise-induced changes in T cell cytokine expression. Although CMV+ mobilized more of the exercise responsive high differentiated T cells than CMV-, this occurred above and below LT. Therefore the augmenting effect of CMV on T cell mobilization is independent of exercise intensity.