Exercise not only imparts broad and lasting benefits to cardiovascular and metabolic health, but also acts as a potent immunomodulator. The dose and intensity of exercise uniquely influence immune cell mobilization, differentiation, and function.
In response to exercise, skeletal muscle releases IL-6, an endocrine myokine and a regulatory factor of immune response. Catecholamines on the other hand signal through beta-adrenergic receptors to stimulate the trafficking of leukocytes. Epinephrine has been repeatedly shown to preferentially impact cytotoxic effector leukocyte populations. Exercise thereby elicits a coordinated set of endocrine responses that shape and tune immunity.
With exercise come hemodynamic changes and neuroendocrine signals derived from catecholamines and glucocorticoids. These physiological modifications can contribute to a doubling and up to a quintupling of leukocytosis. Circulating lymphocytes and monocytes are the first to rise, peaking at the conclusion of exercising before plummeting to below baseline, a phenomena known as transient post-exercise lymphopenia. Neutrophils, in contrast, exhibit a delayed response, gradually increasing and remaining elevated for roughly 24-hrs.
The characteristics of the exercise bout or regimen induce discriminate immunological adaptations. Strenuous exercise can temporarily impair mucosal defense and suppress secretory IgA. Moderate intensity training is more strongly associated with positive impacts, including subdued inflammatory processes and improved immune discernment. As fitness is enhanced and recovery becomes more rapid, so too does the return to homeostasis of the immune system.
Beyond the hemodynamic, catecholamine, and glucocorticoid mediated effects on immune performance, exercise prompts macrophage accumulation and neutrophil redistribution that collectively induce chemokine signaling. This acute inflammatory process is necessary to drive adaptive changes that allow for fitness optimization. Additionally, exercise modulates hematopoiesis by affecting leptin signaling. Chronic training results in a decline in leptin signaling which corresponds with diminished steady-state levels of circulating leukocytes. At the same time, training expands lymphoid progenitors in the bone marrow. In combination, such impacts protect against cardiovascular damage while ensuring a robust response in cases of infection.
As exercise restrains adipose-derived leptin signaling, a shift toward Th17 and T helper 1 polarization occurs, favoring a tolerogenic T regulatory cell response. The adipokines adiponectin, omentin, and apelin are upregulated following training and also promote T cell expansion, IL-10 production, and M2-macrophage polarization, meanwhile repressing NF-kB and NLRP3 signaling. Furthermore, exercise opposes adipose dysfunction by restoring immune cell potency and trafficking. These effects highlight adipose tissue as yet another immunometabolic organ and exercise target that influences immune homeostasis.
Studies indicate that chronic exercise triggers functional immune changes, including immunometabolic reprogramming. Peroxisome proliferator-activated receptor gamma (PPAR-y) is a master metabolic regulator protein that sits at the center of such reprogramming. As VO2 max increases, PPARy stimulation climbs in parallel, exerting an anti-inflammatory benefit. Macrophage polarization toward the M2 phenotype further potentiates anti-inflammatory activities.
These aren’t the only anti-inflammatory signaling pathways implicated in regular exercise training. Mitogen-activated protein kinase phosphatase-1 (MKP-1) interferes with p38 MAPK signaling to prevent tumor necrosis factor alpha (TNFa) and IL-6 cytokine production. IL-6 simultaneously elicits GLP-1 secretion in the intestines and pancreas to initiate insulin release and glycemic regulation. Furthermore, GLP-1 receptors exist on T cells, supporting an immunoregulatory role of the peptide.
Exercise also modulates formation of neutrophil extracellular traps (NATs), structures designed to trap and kill pathogens. When in excess, NATs amplify autoimmune processes, cancer progression, and thrombosis. Lactate accumulation from high intensity training forces a hypoxic metabolic shift and quells reactive oxygen species production to slow NET formation. This contributes to an acute vulnerability to infection but a prolonged barrier to cancer and autoimmunity.
Finally, growing evidence points toward a relationship between exercise and the microbiome in mediating systemic immune effects. The microbial metabolite formate has been elucidated as an immunomodulatory exerkine. Exercise amplifies formate production which in turn potentiates Nrf2 signaling, a redox and metabolic transcription factor. Nrf2 drives cytotoxic CD8 T cell programs that exert antitumor effects. Exercise-induced alterations to the gut microbiome has additionally been correlated with declines in NLRP3 inflammasome activation.
A single high intensity burst of exercise acts as a temporary immunological boost, driving immune cells out of storage and into circulation. Dendritic cells are stimulated to capture antigens and activate T cells, cytotoxic CD8 T cells primed to kill infected or damaged cells rush into the bloodstream, and natural killer-like T cells are mobilized to bolster defense and mount an immune response.
Nevertheless, this storm of immune activity is short-lived, hence the necessity for a combination of both intermittent, high intensity bouts with chronic, moderate-intensity exercise. Long term training balances an acute exercise session, producing a durable rise in CD4 T cells and salivary IgA, remodeling B cells, upregulating antibody response, and improving immunosurveillance. Exploring how to optimally sequence exercise forms to drive beneficial immunological adaptations is a growing area of interest in the context of chronic disease.
Phelps CM, Meisel M. The immunology of exercise: Mechanisms, mediators, and therapeutic opportunities. Immunity. Published online May 21, 2026. doi:10.1016/j.immuni.2026.04.016
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