Effects of Exercise upon Immunoregulation: Facts and a Modern View of its Molecular Mechanisms

The relationship between exercise and the immune system (IS) is a subject that has had widespread attention across time. Both types of behavior, lack of exercise/exhausting exercise, are suggested to weaken immunity. On the contrary, regular moderate exercise seems to boost it. The effects of exercise over the immune responses must be well determined in order to understand how lack of exercise increases the susceptibility to viral, bacterial, and parasitic infections. Nonetheless, we must keep in mind that the relation between physical activity and health is not as direct as it seems, for instance, greater susceptibility to infections after strenuous exercise bouts has been reported, and no impact at all over the immune system is reported during and after low-intensity bouts. Some of the parameters from the immune system that are affected when exercise is performed to exhaustion are: levels of salivary IgA, impaired mitogenic proliferation of lymphocytes, decreased HLA-DR expression, up-regulation of CD14+ cells, variations in CD4+ and CD8+ T lymphocytes proportion, among others. This review discusses the evidence of the effects that exercise elicits on the immune response on different conditions, presenting an updated view about it. Furthermore, we will underline the evidence about the different effects provoked by exercise when performed at distinct intensities and durations. Finally, we will focus on the molecular mechanisms that offer substrate to these interactions and how they help us understand it.