Biphasic changes in leukocytes induced by strenuous exercise

Immune consequences of exercise in hypoxia: A narrative review

Immune outcomes are key mediators of many health benefits of exercise and are determined by exercise type, dose (frequency/duration, intensity), and individual characteristics. Similarly, reduced availability of ambient oxygen (hypoxia) modulates immune functions depending on the hypoxic dose and the individual capacity to respond to hypoxia. How combined exercise and hypoxia (e.g., high-altitude training) sculpts immune responses is not well understood, although such combinations are becoming increasingly popular. Therefore, in this paper, we summarize the impact on immune responses of exercise and of hypoxia, both independently and together, with a focus on specialized cells in the innate and adaptive immune system. We review the regulation of the immune system by tissue oxygen levels and the overlapping and distinct immune responses related to exercise and hypoxia, then we discuss how they may be modulated by nutritional strategies. Mitochondrial, antioxidant, and anti-inflammatory mechanisms underlie many of the adaptations that can lead to improved cellular metabolism, resilience, and overall immune functions by regulating the survival, differentiation, activation, and migration of immune cells. This review shows that exercise and hypoxia can impair or complement/synergize with each other while regulating immune system functions. Appropriate acclimatization, training, and nutritional strategies can be used to avoid risks and tap into the synergistic potentials of the poorly studied immune consequences of exercising in a hypoxic state.

Immunological Response to Exercise in Athletes with Disabilities: A Narrative Review of the Literature

For a person with a disability, participating in sports activities and/or competitions can be a challenge for the immune system. The relationship between exercise and immunity response in disabled athletes is, indeed, extremely complex for several reasons, including (1) the chronic low-grade inflammatory and immunodepression-"secondary immune deficiency"-state imposed by the disability/impairment; (2) the impact of the disability on an array of variables, spanning from physical fitness to well-being, quality of life, sleep, and nutritional aspects, among others, which are known to mediate/modulate the effects of exercise on human health; (3) the variability of the parameters related to the exercise/physical activity (modality, frequency, intensity, duration, training versus competition, etc.); and (4) the intra- and inter-individual variability of the immunological response to exercise. In able-bodied athletes, previously published data described several exercise-induced changes affecting various immunological subsets and subpopulations, ranging from neutrophils to lymphocytes, and monocytes. Broadly, moderate intensity workout is accompanied by optimal immunity and resistance to infections such as upper respiratory tract infections (URTI) in athletes. Periods of intense training with insufficient recovery can cause a temporary state of immunosuppression, which should end with a few days of rest/recovery from exercise. Disabled athletes are relatively overlooked and understudied with respect to their able-bodied counterparts. Findings from the few studies available on paralympic and disabled athletes are here summarized and analyzed utilizing a narrative approach to review and determine the major features of the immunological and inflammatory responses to exercise in this specific population. Moreover, a few studies have reported behavioral, dietary, and training strategies that can be adopted to limit exercise-induced immunosuppression and reduce the risk of infection in people with disabilities. However, given the paucity of data and contrasting findings, future high-quality investigations on paralympic and disabled athletes are urgently needed.

One night of sleep fragmentation does not affect exercise-induced leukocyte trafficking or mitogen-stimulated leukocyte oxidative burst in healthy men

PURPOSE

This study examined whether one night of sleep fragmentation alters circulating leukocyte counts and mitogen-stimulated oxidative burst by leukocytes at rest and in response to an acute bout of vigorous exercise.

METHODS

In a randomised crossover design, nine healthy men (mean ± SD: age 22 ± 2 years; BMI 24.9 ± 1.9 kg/m²) were exposed to one night of fragmented or uninterrupted sleep before cycling for 45 min at 71% ± 4% V̇O_2peak. Finger-tip blood samples were collected at rest, immediately post-exercise and one-hour post-exercise. Total leukocytes, lymphocytes, monocytes and neutrophils were counted. Leukocyte oxidative burst was assessed in whole blood by measuring Reactive Oxygen Species (ROS) production with luminol-amplified chemiluminescence after stimulation with phorbol 12-myristate 13-acetate (PMA).

RESULTS

Exercise elicited the expected trafficking pattern of leukocytes, lymphocytes, monocytes and neutrophils. Compared to rest, PMA-stimulated ROS production was increased one-hour post-exercise (+73% ± 65%; p = 0.019; data combined for fragmented and uninterrupted sleep). There were no statistically significant effects of fragmented sleep on leukocyte, lymphocyte, monocyte, and neutrophil counts or on ROS production at rest, immediately post-exercise or one-hour post-exercise (p > 0.05). However, with fragmented sleep, there was a +10% greater lymphocytosis immediately post-exercise (fragmented +40% ± 37%; uninterrupted +30% ± 35%; p = 0.51) and a -19% smaller neutrophilia by one-hour post-exercise (fragmented +103% ± 88%; uninterrupted +122% ± 131%; p = 0.72).

CONCLUSION

Fragmented sleep did not substantially alter the magnitude or pattern of exercise-induced leukocyte trafficking or mitogen-stimulated oxidative burst by leukocytes.

Does exercise attenuate age- and disease-associated dysfunction in unconventional T cells? Shining a light on overlooked cells in exercise immunology

Unconventional T Cells (UTCs) are a unique population of immune cells that links innate and adaptive immunity. Following activation, UTCs contribute to a host of immunological activities, rapidly responding to microbial and viral infections and playing key roles in tumor suppression. Aging and chronic disease both have been shown to adversely affect UTC numbers and function, with increased inflammation, change in body composition, and physical inactivity potentially contributing to the decline. One possibility to augment circulating UTCs is through increased physical activity. Acute exercise is a potent stimulus leading to the mobilization of immune cells while the benefits of exercise training may include anti-inflammatory effects, reductions in fat mass, and improved fitness. We provide an overview of age-related changes in UTCs, along with chronic diseases that are associated with altered UTC number and function. We summarize how UTCs respond to acute exercise and exercise training and discuss potential mechanisms that may lead to improved frequency and function.

Physical exercise as a tool to help the immune system against COVID-19: an integrative review of the current literature

Acute viral respiratory infections are the main infectious disease in the world. In 2020, a new disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), coronavirus disease 2019 (COVID-19), became a global pandemic. The immune response to the virus depends on factors such as genetics, age and physical state, and its main input receptor is the angiotensin-converting enzyme 2. The practice of physical exercises acts as a modulator of the immune system. During and after physical exercise, pro- and anti-inflammatory cytokines are released, lymphocyte circulation increases, as well as cell recruitment. Such practice has an effect on the lower incidence, intensity of symptoms and mortality in viral infections observed in people who practice physical activity regularly, and its correct execution must be considered to avoid damage. The initial response is given mainly by type I interferons (IFN-I), which drive the action macrophages and lymphocytes, followed by lymphocyte action. A suppression of the IFN-I response has been noted in COVID-19. Severe conditions have been associated with storms of pro-inflammatory cytokines and lymphopenia, as well as circulatory changes and virus dispersion to other organs. The practice of physical activities strengthens the immune system, suggesting a benefit in the response to viral communicable diseases. Thus, regular practice of adequate intensity is suggested as an auxiliary tool in strengthening and preparing the immune system for COVID-19. Further studies are needed to associate physical exercise with SARS-CoV-2 infection.

Physical exercise as a tool to help the immune system against COVID-19: an integrative review of the current literature

Acute viral respiratory infections are the main infectious disease in the world. In 2020, a new disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), coronavirus disease 2019 (COVID-19), became a global pandemic. The immune response to the virus depends on factors such as genetics, age and physical state, and its main input receptor is the angiotensin-converting enzyme 2. The practice of physical exercises acts as a modulator of the immune system. During and after physical exercise, pro- and anti-inflammatory cytokines are released, lymphocyte circulation increases, as well as cell recruitment. Such practice has an effect on the lower incidence, intensity of symptoms and mortality in viral infections observed in people who practice physical activity regularly, and its correct execution must be considered to avoid damage. The initial response is given mainly by type I interferons (IFN-I), which drive the action macrophages and lymphocytes, followed by lymphocyte action. A suppression of the IFN-I response has been noted in COVID-19. Severe conditions have been associated with storms of pro-inflammatory cytokines and lymphopenia, as well as circulatory changes and virus dispersion to other organs. The practice of physical activities strengthens the immune system, suggesting a benefit in the response to viral communicable diseases. Thus, regular practice of adequate intensity is suggested as an auxiliary tool in strengthening and preparing the immune system for COVID-19. Further studies are needed to associate physical exercise with SARS-CoV-2 infection.

Systematic comparison of routine laboratory measurements with in-hospital mortality: ICU-Labome, a large cohort study of critically ill patients

BACKGROUND

In intensive care unit (ICU) patients, many laboratory measurements can be deranged when compared with the standard reference interval (RI). The assumption that larger derangements are associated with worse outcome may not always be correct. The ICU-Labome study systematically evaluated the univariate association of routine laboratory measurements with outcome.

METHODS

We studied the 35 most frequent blood-based measurements in adults admitted ≥6 h to our ICU between 1992 and 2013. Measurements were from the first 14 ICU days and before ICU admission. Various metrics, including variability, were related with hospital survival. ICU- based RIs were derived from measurements obtained at ICU discharge in patients who were not readmitted to the ICU and survived for >1 year.

RESULTS

In 49,464 patients (cardiothoracic surgery 43%), we assessed >20·106 measurements. ICU readmissions, in-hospital and 1-year mortality were 13%, 14% and 19%, respectively. On ICU admission, lactate had the strongest relation with hospital mortality. Variability was independently related with hospital mortality in 30 of 35 measurements, and 16 of 35 measurements displayed a U-shaped outcome-relation. Medians of 14 of 35 ICU-based ranges were outside the standard RI. Remarkably, γ-glutamyltransferase (GGT) had a paradoxical relation with hospital mortality in the second ICU week because more abnormal GGT-levels were observed in hospital survivors.

CONCLUSIONS

ICU-based RIs for may be more useful than standard RIs in identifying ICU patients at risk. The association of variability with outcome for most of the measurements suggests this is a consequence and not a cause of a worse ICU outcome. Late elevation of GGT may confer protection to ICU patients.

Potential use of leukocytosis and anion gap elevation in differentiating psychogenic nonepileptic seizures from epileptic seizures

Epileptic seizures (ES) and psychogenic nonepileptic seizures (PNES) can be difficult to differentiate from each other in the emergency department (ED) setting. We have previously shown that the anion gap (AG) can help differentiate between ES and PNES in the ED. In this study, we explored whether additionally considering leukocytosis can help better differentiate between ES and PNES. We screened a total of 1354 subjects seen in the ED of a tertiary care medical center; 27 PNES and 27 ES patients were identified based on clinical description and subsequent electroencephalography (EEG). Multivariable logistic regression analysis was used to model the association between ES, leukocytosis, and AG. Our results indicated that within 9 hours after the index event, serum AG (adjusted odds ratio [aOR] 2.07) and white blood cell (WBC) count (aOR 1.61) were both independently associated with ES. We derived an equation to help differentiate between ES and PNES: 1.5*AG+WBC. A score >24.8 indicated a >90% likelihood of ES. A score <15.5 indicated a <10% likelihood of ES (ie, the alternate diagnosis of PNES should be considered). This study for the first time provides evidence to help differentiate PNES and ES utilizing acidosis and leukocytosis.

Acute aerobic exercise induces a preferential mobilisation of plasmacytoid dendritic cells into the peripheral blood in man

Dendritic cells (DCs) are important sentinel cells of the immune system responsible for presenting antigen to T cells. Exercise is known to cause an acute and transient increase in the frequency of DCs in the bloodstream in humans, yet there are contradictory findings in the literature regarding the phenotypic composition of DCs mobilised during exercise, which may have implications for immune regulation and health. Accordingly, we sought to investigate the composition of DC sub-populations mobilised in response to acute aerobic exercise. Nine healthy males (age, 21.9 ± 3.6 years; height, 177.8 ± 5.4 cm; body mass, 78.9 ± 10.8 kg; body mass index, 24.9 ± 3.3 kg·m²; V̇O_{2 MAX}, 41.5 ± 5.1 mL·kg·min^-1) cycled for 20 min at 80% V̇O_{2 MAX}. Blood was sampled at baseline, during the final minute of exercise and 30 min later. Using flow cytometry, total DCs were defined as Lineage- (CD3, CD19, CD20, CD14, CD56) HLA-DR+ and subsequently identified as plasmacytoid DCs (CD303+) and myeloid DCs (CD303-). Myeloid DCs were analysed for expression of CD1c and CD141 to yield four sub-populations; CD1c-CD141+; CD1c+CD141+; CD1c+CD141- and CD1c-CD141-. Expression of CD205 was also analysed on all DC sub-populations to identify DCs capable of recognising apoptotic and necrotic cells. Total DCs increased by 150% during exercise (F_(1,10) = 60; p < 0.05, η² = 0.9). Plasmacytoid DCs mobilised to a greater magnitude than myeloid DCs (195 ± 131% vs. 131 ± 100%; p < 0.05). Among myeloid DCs, CD1c-CD141- cells showed the largest exercise-induced mobilisation (167 ± 122%), with a stepwise pattern observed among the remaining sub-populations: CD1c+CD141- (79 ± 50%), followed by CD1c+CD141+ (44 ± 41%), with the smallest response shown by CD1c-CD141+ cells (23 ± 54%) (p < 0.05). Among myeloid DCs, CD205- cells were the most exercise responsive. All DC subsets returned to resting levels within 30 min of exercise cessation. These results show that there is a preferential mobilisation of plasmacytoid DCs during exercise. Given the functional repertoire of plasmacytoid DCs, which includes the production of interferons against viral and bacterial pathogens, these findings indicate that exercise may augment immune-surveillance by preferentially mobilising effector cells; these findings have general implications for the promotion of exercise for health, and specifically for the optimisation of DC harvest for cancer immunotherapy.

N1-methylnicotinamide (MNAM) as a guardian of cardiovascular system

Atherosclerosis is identified as the formation of atherosclerotic plaques, which could initiate the formation of a blood clot in which its growth to coronary artery can lead to a heart attack. N-methyltransferase (NNMT) is an enzyme that converts the NAM (nicotinamide) to its methylated form, N1-methylnicotinamide (MNAM). Higher levels of MNAM have been reported in cases with coronary artery disease (CAD). Further, MNAM increases endothelial prostacyclin (PGI2) and nitric oxide (NO) and thereby causes vasorelaxation. The vasoprotective, anti-inflammatory and anti-thrombotic roles of MNAM have been well documented; however, the exact underlying mechanisms remain to be clarified. Due to potential role of MNAM in the formation of lipid droplets (LDs), it might exert its function in coordination with lipids, and their targets. In this study, we summarized the roles of MNAM in cardiovascular system and highlighted its possible mode of actions.

Debunking the Myth of Exercise-Induced Immune Suppression: Redefining the Impact of Exercise on Immunological Health Across the Lifespan

Epidemiological evidence indicates that regular physical activity and/or frequent structured exercise reduces the incidence of many chronic diseases in older age, including communicable diseases such as viral and bacterial infections, as well as non-communicable diseases such as cancer and chronic inflammatory disorders. Despite the apparent health benefits achieved by leading an active lifestyle, which imply that regular physical activity and frequent exercise enhance immune competency and regulation, the effect of a single bout of exercise on immune function remains a controversial topic. Indeed, to this day, it is perceived by many that a vigorous bout of exercise can temporarily suppress immune function. In the first part of this review, we deconstruct the key pillars which lay the foundation to this theory-referred to as the "open window" hypothesis-and highlight that: (i) limited reliable evidence exists to support the claim that vigorous exercise heightens risk of opportunistic infections; (ii) purported changes to mucosal immunity, namely salivary IgA levels, after exercise do not signpost a period of immune suppression; and (iii) the dramatic reductions to lymphocyte numbers and function 1-2 h after exercise reflects a transient and time-dependent redistribution of immune cells to peripheral tissues, resulting in a heightened state of immune surveillance and immune regulation, as opposed to immune suppression. In the second part of this review, we provide evidence that frequent exercise enhances-rather than suppresses-immune competency, and highlight key findings from human vaccination studies which show heightened responses to bacterial and viral antigens following bouts of exercise. Finally, in the third part of this review, we highlight that regular physical activity and frequent exercise might limit or delay aging of the immune system, providing further evidence that exercise is beneficial for immunological health. In summary, the over-arching aim of this review is to rebalance opinion over the perceived relationships between exercise and immune function. We emphasize that it is a misconception to label any form of acute exercise as immunosuppressive, and, instead, exercise most likely improves immune competency across the lifespan.

High Volume Exercise Training in Older Athletes Influences Inflammatory and Redox Responses to Acute Exercise

To examine whether the volume of previous exercise training in older athletes influences inflammatory, redox, and hormonal profiles, 40 trained marathon runners were divided into higher-volume (HVG, ∼480 min/week) and lower-volume groups (LVG, ∼240 min/week). Plasma inflammatory proteins, redox biomarkers, salivary testosterone, and cortisol were assessed at restand following two maximal acute exercise bouts. At rest, the LVG exhibited higher CRP, higher protein carbonyls, and lower SOD activity compared to the HVG (p's < .05). In response to exercise, TNF-α declined similarly in both groups whereas CRP increased differentially (+60% LVG; +24% HVG; p's < .05). Protein carbonyls decreased and thiols increased similarly in both groups, but SOD declined differentially between groups (-14% LVG; -20% HVG; p's < .05). Salivary testosterone decreased similarly in both groups, whereas cortisol did not change. A higher volume of training is associated with favorable inflammatory and redox profiles at rest, perhaps mediated by small inflammatory responses to acute exercise.

Maximal exercise increases mucosal associated invariant T cell frequency and number in healthy young men

PURPOSE

Mucosal associated invariant T (MAIT) cells have properties of the innate and acquired immune systems. While the response to vigorous exercise has been established for most leukocytes, MAIT cells have not been investigated. Therefore, the purpose was to determine if MAIT cell lymphocytosis occurs with acute maximal aerobic exercise and if this response is influenced by exercise duration, cardiovascular fitness, or body composition.

METHODS

Twenty healthy young males with moderate fitness levels performed an extended graded exercise test until volitional fatigue. Peripheral blood mononuclear cells were isolated from venous blood obtained prior and immediately after exercise and were labeled to identify specific T cell populations using flow cytometry.

RESULTS

The percentage of MAIT cells relative to total T cells significantly increased from 3.0 to 3.8% and absolute MAIT cell counts increased by 2.2-fold following maximal exercise. MAIT cell subpopulation proportions were unchanged with exercise. Within cytotoxic T lymphocytes (CTL), MAIT cells consisted of 8% of these cells and this remained constant after exercise. MAIT cell counts and changes with exercise were not affected by body composition, VO_2peak, or exercise duration.

CONCLUSIONS

Maximal exercise doubled MAIT cell numbers and showed preferential mobilization within total T cells but the response was not influenced by fitness levels, exercise duration, or body composition. These results suggest that acute exercise could be used to offset MAIT cell deficiencies observed with certain pathologies. MAIT cells also make up a substantial proportion of CTLs, which may have implications for cytotoxicity assays using these cells.

Immune biomarkers in older adults: Role of physical activity

Aging is associated with a decline in the normal functioning of the immune system. Several studies described the relationship between immunological alterations, including immunosenescence and inflammation, and aging or age-related outcomes, such as sarcopenia, depression, and neurodegenerative disorders. Physical activity is known to improve muscle function and to exert a number of benefits on older adult health, including reduced risk for heart and metabolic system chronic diseases. However, the positive influence of physical activity on the immune system has not been elucidated. In order to shed light on the role of physical activity in immune responses of older individuals, a number of immunological parameters comprising % lymphocyte subsets (CD3⁺, CD4⁺, CD8⁺, CD19⁺, and CD16⁺56⁺) and serum levels of neopterin and tryptophan metabolism products were evaluated in peripheral blood samples of older adults performing normal (N = 170) or reduced (N = 89) physical activity. In addition, the potential influence of other clinical and epidemiological factors was also considered. Results showed that subjects with reduced physical activity displayed significantly higher levels of CD4⁺/CD8⁺ ratio, kynurenine/tryptophan ratio, and serum neopterin, along with lower %CD19⁺ cells and tryptophan concentrations. Further, some immunological biomarkers were associated with cognitive impairment and functional status. These data contribute to reinforce the postulation that physical activity supports healthy aging, particularly by helping to protect the immunological system from aging-related changes.

Acute high-intensity interval exercise reduces human monocyte Toll-like receptor 2 expression in type 2 diabetes

Type 2 diabetes (T2D) is characterized by chronic low-grade inflammation that contributes to disease pathophysiology. Exercise has anti-inflammatory effects, but the impact of high-intensity interval training (HIIT) is not known. The purpose of this study was to determine the impact of a single session of HIIT on cellular, molecular, and circulating markers of inflammation in individuals with T2D. Participants with T2D (n = 10) and healthy age-matched controls (HC; n = 9) completed an acute bout of HIIT (7 × 1 min at ~85% maximal aerobic power output, separated by 1 min of recovery) on a cycle ergometer with blood samples obtained before (Pre), immediately after (Post), and at 1 h of recovery (1-h Post). Inflammatory markers on leukocytes were measured by flow cytometry, and TNF-α was assessed in both LPS-stimulated whole blood cultures and plasma. A single session of HIIT had an overall anti-inflammatory effect, as evidenced by 1) significantly lower levels of Toll-like receptor (TLR) 2 surface protein expression on both classical and CD16+ monocytes assessed at Post and 1-h Post compared with Pre (P < 0.05 for all); 2) significantly lower LPS-stimulated TNF-α release in whole blood cultures at 1-h Post (P < 0.05 vs. Pre); and 3) significantly lower levels of plasma TNF-α at 1-h Post (P < 0.05 vs. Pre). There were no differences between T2D and HC, except for a larger decrease in plasma TNF-α in HC vs. T2D (group × time interaction, P < 0.05). One session of low-volume HIIT has immunomodulatory effects and provides potential anti-inflammatory benefits to people with, and without, T2D.

Exercise-induced B cell mobilisation: Preliminary evidence for an influx of immature cells into the bloodstream

The number of peripheral blood B lymphocytes doubles during acute exercise, but the phenotypic composition of this response remains unknown. In two independent exercise studies, using complimentary phenotyping strategies, we investigated the mobilisation patterns of distinct B cell subsets. In study one, nine healthy males (mean±SD age: 22.1±3.4years) completed a continuous cycling bout at 80% V̇O2MAX for 20min. In study two, seven healthy experienced cyclists (mean±SD age: 29.9±4.7years) completed a 30min cycling trial at a workload corresponding to +5% of the individual blood lactate threshold. In study one, CD3-CD19+ B cell subsets were classified into immature (CD27-CD10+), naïve (CD27-CD10-), memory (CD27+CD38-), plasma cells/plasmablasts (CD27+CD38+) and finally, recently purported 'B1' cells (CD27+ CD43+ CD69-). In study two, CD20+ B cells were classified into immature (CD27-IgD-), naïve (CD27-IgD+), and IgM+/IgG+/IgA+ memory cells (CD27+IgD-). Total B cells exhibited a mean increase of 88% (study one) and 60% (study two) during exercise. In both studies, immature cells displayed the greatest increase, followed by memory cells, then naïve cells (study one: immature 130%>mature 105%>naïve 84%; study two: immature 110%>mature 56%>naïve 38%). Our findings show that, unlike T cells and NK cells, B cell mobilisation is not driven by effector status, and, for the first time, that B cell mobilisation during exercise is comprised of immature CD27- IgD-/CD10+ cells.

Effects of 1-Methylnicotinamide (MNA) on Exercise Capacity and Endothelial Response in Diabetic Mice

1-Methylnicotinamide (MNA), which was initially considered to be a biologically inactive endogenous metabolite of nicotinamide, has emerged as an anti-thrombotic and anti-inflammatory agent with the capacity to release prostacyclin (PGI2). In the present study, we characterized the effects of MNA on exercise capacity and the endothelial response to exercise in diabetic mice. Eight-week-old db/db mice were untreated or treated with MNA for 4 weeks (100 mg·kg-1), and their exercise capacity as well as NO- and PGI2-dependent response to endurance running were subsequently assessed. MNA treatment of db/db mice resulted in four-fold and three-fold elevation of urine concentrations of MNA and its metabolites (Met-2PY + Met-4PY), respectively (P<0.01), but did not affect HbA1c concentration, fasting glucose concentration or lipid profile. However, insulin sensitivity was improved (P<0.01). In MNA-treated db/db mice, the time to fatigue for endurance exercise was significantly prolonged (P<0.05). Post-exercise Δ6-keto-PGF1α (difference between mean concentration in the sedentary and exercised groups) tended to increase, and post-exercise leukocytosis was substantially reduced in MNA-treated animals. In turn, the post-exercise fall in plasma concentration of nitrate was not affected by MNA. In conclusion, we demonstrated for the first time that MNA improves endurance exercise capacity in mice with diabetes, and may also decrease the cardiovascular risk of exercise.

Effects of exercise on leukocytosis and blood hemostasis in 800 healthy young females and males

AIM: To investigate the effects of exercise on healthy individuals of both genders.

METHODS: This study lasted 6 years and involved about 800 healthy people. Individuals were divided into females and males and further sub-divided into two groups; in the first group individuals run (or skied in the winter time) and then rested for 3 h, whereas individuals in the second group intensely cycled for 5 min. The status of health was determined by measuring the sedimentation rate and the intensity of exercises by measuring the heart rate. Blood samples were collected before and after exercise.

RESULTS: We observed that in the first group a significant increase of the total white blood cells, segmented neutrophils, band neutrophils, eosinophils and to a lesser extent lymphocytes but not monocytes in the blood circulation. However, all cell types were increased in the circulation after 5 min intense exercise. No differences in the pattern of cell increase were observed among the genders. Activated partial thromboplastin time (APTT) and D-dimer were also measured in the blood of individuals who cycled intensely for 5 min to determine the coagulation and fibrinolytic activities in the blood. APTT is reduced and D-dimer values significantly increased after intense exercise. However, APTT was statistically lower in males than females, whereas no differences in the D-dimer values were observed among the genders.

CONCLUSION: Our results indicate that exercise whether leisure or strenuous affects leukocytosis and hemostasis in both genders. A major advantage of this study is the high numbers of individuals involved and the inclusion of both females and males values.

Inflammatory response to strenuous muscular exercise in man

Based on the humoral and cellular changes occurring during strenuous muscular work in humans, the concept of inflammatory response to exercise (IRE) is developed. The main indices of IRE consist of signs of an acute phase response, leucocytosis and leucocyte activation, release of inflammatory mediators, tissue damage and cellular infiltrates, production of free radicals, activation of complement, and coagulation and fibrinolytic pathways. Depending on exercise intensity and duration, it seems likely that muscle and/or associated connective tissue damage, contact system activation due to shear stress on endothelium and endotoxaemia could be the triggering mechanisms of IRE. Although this phenomenon can be considered in most cases as a physiological process associated with tissue repair, exaggerated IRE could have physiopathological consequences. On the other hand, the influence of several factors such as age, sex, training, hormonal status, nutrition, anti-inflammatory drugs, and the extent to which IRE could be a potential risk for subjects undergoing intense physical training require further study.

Efeito do exercício no sistema imune: resposta, adaptação e sinalização celular

INTRODUÇÃO: Durante o último século, o homem tornou-se menos ativo fisicamente, adotando hábitos cada vez mais sedentários. Isto promoveu aumento na incidência de doenças crônicas tais como doenças cardiovasculares, diabetes do tipo 2 e síndrome metabólica. A prática de atividade física pode influenciar o estado de higidez alterando estados metabólicos e também o sistema imunológico. OBJETIVO: Revisar na literatura estudos que abordem os efeitos promovidos pelo exercício físico no desenvolvimento da resposta imunológica e suas possíveis vias de transdução de sinais. MÉTODOS: Foram consultadas as bases de dados SciELO e PubMed. RESULTADOS: A literatura disponível mostra que durante a prática de exercício, várias subpopulações de leucócitos são alteradas de acordo com a intensidade e duração da atividade desempenhada. Exercícios de intensidade moderada estimulam uma resposta pró-inflamatória, enquanto aqueles de alta intensidade tendem a promover respostas anti-inflamatórias visando diminuir os danos na musculatura esquelética. Tais alterações são vistas em células apresentadoras de antígeno (como macrófagos e células dendríticas), neutrófilos, células natural killers (NK) e em moléculas de superfície como os receptores do tipo Toll (TLR) e do complexo principal de histocompatibilidade de classe II (MHC II), além das modificações promovidas em todo o repertório de citocinas. CONCLUSÃO: O estado atual do conhecimento permite considerar que as alterações no sistema imune são dependentes dos parâmetros inerentes ao exercício e que para que todas estas alterações ocorram, algumas cascatas de sinalização celular são acionadas, dando origem a um complexo processo de fosforilação/desfosforilação que culmina em ativação de fatores de transcrição, tradução de RNAm, síntese proteica e proliferação celular.

[Changes in neutrophil immune functions under different exercise stresses]

The aim of this review is to provide a summary of the known effects of exercise on neutrophil immune functions of athletes. We measured three neutrophil immune functions (i.e., phagocytic activity (PA), reactive oxygen species (ROS) production, and serum opsonic activity (SOA)) in various types of exercise. The following is our recent findings. (1) A regular exercise increases ROS production and decreases PA. We call this change a normal pattern, and an abnormal pattern except this change. (2) A prolonged, strenuous activity (e.g., rugby match and marathon) decreases both ROS production and PA. This is one of the abnormal pattern. (3) The exercise loading performed after a camp training decreases ROS production whereas PA does not change. This is another abnormal pattern. (4) When judoists who had stopped judo training for 6 months restarted their training, the exercise loading at the beginning of their training decreases PA whereas ROS production does not change. This is another abnormal pattern. (5) A regular exercise 2 months after the beginning of their training increases ROS production and decreases PA. This change is a normal pattern. SOA showed a similar pattern of changes to ROS under all conditions. The changes in neutrophil immune functions after performing various exercises might result from the balance between external factors (intensity and style of exercise) and internal factors (e.g., fatigue and physical pain). Therefore, the changes in three neutrophil immune functions after exercise might be an index of athletes' condition.

Latent cytomegalovirus infection amplifies CD8 T-lymphocyte mobilisation and egress in response to exercise

Exercise induces mobilisation of CD8(+) T lymphocytes (CD8TL) into the peripheral blood. This response is largely confined to effector-memory CD8TLs: antigen experienced cells which have a strong tissue-homing and effector potential. This study investigated whether effector-memory cells also account for the CD8TL egress from peripheral blood following exercise. As latent Cytomegalovirus (CMV) infection is associated with a robust expansion in the number and proportion of effector-memory CD8TLs, we also investigated if CMV serostatus was a determinant of the CD8TL responses to exercise. Fourteen males (Mean age 35, SD ± 14 yrs), half of whom were CMV seropositive (CMV(+)), ran on a treadmill for 60 min at 80% VO(2) max. Blood was collected at baseline, during the final minute of exercise, and 15 min and 60 min thereafter. CD8TL memory subsets were characterised by flow cytometry, using the cell-surface markers CD45RA, CD27, and CD28. The results confirmed that CD8TLs with an effector-memory phenotype (CD27(-)CD28(-)CD45RA(+/-)) exhibited the largest increase during exercise (+200% to +250%), and also showed the largest egress from blood 60 min post-exercise (down to 40% of baseline values). Strikingly, the mobilisation and subsequent egress of total CD8TLs was nearly twice as large in CMV(+) individuals. This effect appeared specific to CD8TLs, and was not seen for CD4(+) T lymphocytes or total lymphocytes. This effect of CMV serostatus was largely driven by the higher numbers of exercise-responsive effector-memory CD8TLs in the CMV(+) participants. This is the first study to demonstrate that infection history is a determinant of immune system responses to exercise.

Exercise-induced immune cell apoptosis: image-based model for morphological assessment

Methods of assessing exercise-induced lymphocyte apoptosis have produced varying results. While morphological methods generally yield a significantly greater apoptotic index compared to those employing biochemical markers, benefits and limitations are associated with each methodology. Of interest in this report is the limitation of subjectivity associated with the morphological technique. To overcome the lack of objectivity associated with the morphological method, we describe an image-based approach by which computer software assesses the characteristics associated with lymphocyte apoptosis. A stochastic controlled deformable model can be employed to detect the classic morphological apoptotic changes induced by exercise, including membrane blebbing and the formation of apoptotic bodies. We propose that an objective evaluation of multiple points in the apoptotic process through the proposed model in conjunction with current biomarker methods has the potential to advance our understanding of the exercise-induced immune cell death response to a greater degree than current methods.

Immune Response to Resistance Exercise

Resistance exercise produces transient perturbations in immunity, including alterations in circulating leukocyte numbers, cytokine concentration, and some measures of cell function. These changes are typically interpreted as being transiently detrimental to host defense. The mechanisms responsible for these immune fluctuations appear to be neuroendocrine-mediated alterations in cell trafficking and function and microtrauma-mediated alterations in cytokine release. Alterations in immunity following resistance exercise appear to be similar in pattern but smaller in magnitude than those typically seen after long, vigorous endurance exercise and are resolved within a few hours. However, resistance exercise—induced changes in immunity may become clinically relevant after repeated exercise bouts with insufficient recovery. Regular training appears to attenuate the immune response to resistance exercise. Care should be taken to ensure that resistance training is planned, with adequate variation in intensity and volume over time, to ensure recovery between sessions and to avoid chronic systemic inflammation.

Differential Response of Lymphocytes and Neutrophils to High Intensity Physical Activity and to Vitamin C Diet Supplementation

We have determined the effects of chronic vitamin C intake on neutrophil and lymphocyte antioxidant defences during the acute phase immune response induced by intense exercise. Blood samples were taken from 16 voluntary athletes in basal conditions, both immediately after and 1 h after a duathlon competition. Sportsmen's nutrient intakes were determined before the competition. After determining the basal plasmatic ascorbate levels, the results were analysed taking into account the vitamin C intake and their plasmatic levels. Two groups were constituted, the vitamin C supplemented group and the control group, with the dietary vitamin C intake as the only statistical difference between groups. The duathlon competition induced a significant neutrophilia, which was higher in the supplemented group. Lymphocyte antioxidant enzyme activities increased after the competition, with a higher increase in SOD activity in the control group than in the supplemented one. The competition decreased neutrophil antioxidant enzyme activities and neutrophil ascorbate concentration. The decrease in the SOD activity in the supplemented group was higher than in the control group. Finally, the duathlon competition increased the expression of MAC-1 neutrophil adhesion molecule in the supplemented group. High vitamin C intake influenced the response of neutrophils and lymphocytes to oxidative stress induced by exercise, increasing the neutrophil activation.

Sustained leukocyte count during rising cortisol level

AIMS

To follow the trend of leukocyte counts relative to the serum cortisol levels in hospitalized patients.

METHODS

We retrospectively reviewed the charts of 59 hospitalized patients who had sequential blood profiles during a 2-week period.

RESULTS

The study cohort was divided into two subgroups according to the categorical cortisol levels: those within the normal range (< 25 microg/dl; n = 31 patients) and those above the normal range (> or = 25 microg/dl; n = 28 patients). The baseline white blood cell counts (WBCCs) were similar in both groups. After 1 week, however, the WBCCs dropped significantly in the presence of normal cortisol levels and increased in the presence of elevated cortisol levels (p = 0.002). This pattern was not followed by the platelet counts. A significant correlation was observed between the cortisol levels and the 1 week concomitant WBCC (r = 0.33).

CONCLUSION

Cortisol may be the mechanism with a positive effect on the maintenance of elevated leukocyte counts.

Differential response of plasma and immune cell's vitamin E levels to physical activity and antioxidant vitamin supplementation

OBJECTIVE

To assess the differential response of plasma, lymphocyte and neutrophil vitamin E levels to high-intensity physical activity and to vitamin C and E supplementation.

SUBJECTS

In all, 14 male trained amateur runners (32-36 y old) were randomly divided in two groups (supplemented and placebo), and participated in a half marathon race. The subjects did not take any other supplements than the ones provided for this study.

INTERVENTION

Vitamin C (152 mg/day) and E (50 mg/day) supplementation was administrated to athletes for a month, using a new almond-based isotonic and energetic beverage (supplemented group). The usual dietary habits of participants were assessed using a self-reported 7-day 24-h recall before the day of the study. To avoid the beverage influence, nonenriched vitamin C and E almond-based isotonic and energetic beverage was given to the placebo group. After 1 month, subjects participated in a half marathon race (21 km run). Vitamin E concentration was determined in plasma, neutrophils and lymphocytes before and immediately after the race, and 3 h after finishing the race.

RESULTS

Daily energy intake and caloric profile of supplemented and placebo group were not different except for vitamin C and E supplementation. Vitamin supplementation and exercise had no effect on vitamins E levels in plasma. The exercise significantly (P<0.05) increased the lymphocyte vitamin E concentration both in the placebo (+119%) and supplemented groups (+128%), and neutrophil vitamin E content in the supplemented group (+88%). These levels remained significantly (P<0.05) high after the short recovery. After exercise, vitamin E levels in lymphocytes and neutrophils of supplemented subjects were practically twice the levels before exercise, whereas neutrophil vitamin E content of the placebo group was close to those in plasma.

CONCLUSION

After endurance exercise, lymphocytes increased their vitamin E content in the supplemented and placebo subjects whereas this trend in neutrophils was just observed in the supplemented group. The determination of vitamin E content in lymphocytes and neutrophils after exercise is a useful tool to assess the functional status of vitamin E.

Granule Localization of Glutaminase in Human Neutrophils and the Consequence of Glutamine Utilization for Neutrophil Activity

The provision of glutamine in vivo has been observed to reduce to normal levels the neutrophilia observed after exhaustive exercise and to decrease the neutrophil chemoattractant, interleukin-8. Thus, the role for glutamine in the regulation of inflammatory mediators of human neutrophil activation was investigated. The study sought to establish whether glutamine supplementation in vitro affects neutrophil function at rest and whether glutaminase, the major enzyme that metabolizes glutamine, is present in human polymorphonuclear neutrophils (PMN). During in vitro studies, the addition of 2 mm glutamine increased the respiratory burst of human PMN stimulated with both phorbol myristate acetate (PMA) and formyl-methionyl-leucyl-phenylalanine. These observations were made using a highly sensitive, real time chemiluminescent probe, Pholasin. Glutamine alone did not stimulate the release of reactive oxygen species. In a novel finding using glutaminase-specific antibodies in combination with flow cytometry and confocal microscopy, glutaminase was shown to be present on the surface of human PMN. Subcellular fractionation revealed that the enzyme was enriched in the secondary granules and could be released into cell culture medium upon stimulation with PMA. In conclusion, human PMN appeared to utilize glutamine and possess the appropriate glutaminase enzyme for metabolizing glutamine. This may depress some pro-inflammatory factors that occur during prolonged, exhaustive exercise.

Delayed leukocytosis after hard strength and endurance exercise: aspects of regulatory mechanisms

Background

During infections, polymorphonuclear neutrophilic granulocytes (PMN) are mobilized from their bone marrow stores, travel with blood to the affected tissue, and kill invading microbes there. The signal(s) from the inflammatory site to the marrow are unknown, even though a number of humoral factors that can mobilize PMN, are well known. We have employed a standardized, non-infectious human model to elucidate relevant PMN mobilizers. Well-trained athletes performed a 60-min strenuous strength workout of leg muscles. Blood samples were drawn before, during and just after exercise, and then repeatedly during the following day. Cortisol, GH, ACTH, complement factors, high-sensitive CRP (muCRP), IL-6, G-CSF, IL-8 (CXCL8) and MIP-1β (CCL4) were measured in blood samples. PMN chemotaxins in test plasma was assessed with a micropore membrane technique.

Results

About 5 hr after the workout, blood granulocytosis peaked to about 150% of baseline. Plasma levels of GH increased significantly 30 min into and 5 min after the exercise, but no increase was recorded for the other hormones. No significant correlation was found between concentrations of stress hormones and the subjects' later occurring PMN increases above their individual baselines. Plasma G-CSF increased significantly – but within the normal range – 65 min after the workout. IL-6 increased very slightly within the normal range, and the chemokines IL-8 and MIP-1β did not increase consistently. However, we found a significant increase of hitherto non-identified PMN-chemotactic activity in plasma 35, 50, and 60 min after the exercise. No systemic complement activation was detected, and (mu)CRP was within the reference range at rest, 5 h and 23 h after the exercise. After endurance exercise, similar findings were made, except for a cortisol response, especially from non-elite runners.

Conclusion

Apparently, a multitude of humoral factors can – directly or indirectly – mobilize PMN from marrow to blood; some of the factors are, others are not known to be, chemotactic. Under different conditions, different selections of these mobilizers may be used. In the late granulocytosis after heavy, long-lasting exercise a number of factors thought capable of mimicking the granulocytosis of infectious diseases were apparently irrelevant.

Glutamine supplementation in vitro and in vivo, in exercise and in immunodepression

In situations of stress, such as clinical trauma, starvation or prolonged, strenuous exercise, the concentration of glutamine in the blood is decreased, often substantially. In endurance athletes this decrease occurs concomitantly with relatively transient immunodepression. Glutamine is used as a fuel by some cells of the immune system. Provision of glutamine or a glutamine precursor, such as branched chain amino acids, has been seen to have a beneficial effect on gut function, on morbidity and mortality, and on some aspects of immune cell function in clinical studies. It has also been seen to decrease the self-reported incidence of illness in endurance athletes. So far, there is no firm evidence as to precisely which aspect of the immune system is affected by glutamine feeding during the transient immunodepression that occurs after prolonged, strenuous exercise. However, there is increasing evidence that neutrophils may be implicated. Other aspects of glutamine and glutamine supplementation are also addressed.

Can glutamine modify the apparent immunodepression observed after prolonged, exhaustive exercise?

Glutamine is an important fuel for some cells of the immune system. In situations of stress, such as clinical trauma, starvation, or prolonged, strenuous exercise, the concentration of glutamine in blood is decreased, often substantially. In endurance athletes this decrease occurs concomitantly with relatively transient immunodepression. Provision of glutamine or a glutamine precursor has been found to decrease the incidence of illness in endurance athletes. To date, it has not been established precisely which aspect of the immune system is affected by glutamine feeding during the transient immunodepression that occurs after prolonged, strenuous exercise. However, there is increasing evidence that neutrophils may be implicated.

Sepsis and mechanisms of inflammatory response: is exercise a good model?

OBJECTIVES

The immune changes induced by a bout of prolonged and vigorous exercise have been suggested to be a useful experimental model of sepsis and the inflammatory response. Available literature was reviewed to evaluate this hypothesis.

METHODS

Literature describing the immune response to various patterns of exercise was compared with data on the immune changes observed during sepsis and inflammation.

RESULTS

Although there are qualitative similarities between the immune responses to exercise and sepsis, the magnitude of the changes induced by most forms of exercise remains much smaller than in a typical inflammatory response. Indeed, the exercise induced changes in some key elements such as plasma cytokine concentrations are too small to be detected reliably by current technology.

CONCLUSIONS

If exercise is to provide a valid model of sepsis and the inflammatory response, it will be necessary to focus on subjects who are willing to exercise extremely hard, to use the pattern of exercise that has the greatest effect on the immune system, and to combine this stimulus with other psychological, environmental, or nutritional stressors.

Neutrophil response to prolonged exercise in immune-competent and RAG2/γc null mice

The two aims of this study were (i) to compare the effects of prolonged exercise on circulating neutrophil number and muscle myeloperoxidase (MPO) activity between RAG2/γc null and immune-competent mice, and (ii) to evaluate the general suitability of the lymphocyte-deficient RAG2/γc null strain for use in exercise models of immune regulation. RAG2/γc null (male and female) and C57BL/6 (congenic immune-competent, male) mice were assigned to either control (C) or treadmill exercise (EX, 22 m/min, 90 min, 6% grade) groups. EX mice were killed immediately (EX0) or 24 h (EX24) after exercise. RAG2/γc null males had significantly (P < 0.05) fewer circulating CD45+ cells and higher %CD45+ neutrophils than did C57BL/6 males, independent of exercise. A significant interaction was observed for the effects of exercise and gender on %CD45+ neutrophils in the blood. At EX24, gastrocnemius (Gastroc) MPO significantly increased in EX mice. Gastroc MPO activity was 44% and 35% higher in RAG2/γc null vs. C57BL/6 males, and in female vs. male RAG2/γc null mice, respectively. Heart MPO activity did not differ between strains or among treatments. We concluded that the Rag2/γc null strain is a suitable model for future investigations on immune regulation following acute exercise stress.Key words: treadmill exercise, neutrophils, immune-deficient, RAG2/γc null mice.

Production of reactive oxygen species in neutrophils after repeated bouts of exercise in standardbred trotters

Six trained Standardbred trotters exercised on a racetrack on 2 days with a 3-day interval. On both exercise days the horses trotted three different exercise bouts with increasing intensity with 60-min intervals. Exercise-induced stress was manifested as leucocytosis, an increase in the neutrophil:lymphocyte (N:L) ratio, and increased capacity to produce reactive oxygen species in the peripheral blood as indicated by an increase in whole blood chemiluminescence. The leucocytosis was mainly due to neutrophilia, which lasted for 6 h. Production of reactive oxygen species per single neutrophil showed no significant change during a day of exercise, but was lower on the second exercise day. The cortisol concentrations and N:L ratio, used as indicators of stress, behaved differently: Cortisol did not change significantly after exercise, whereas the N:L ratio increased. These results suggest that in trained horses, the N:L ratio is a sensitive indicator of stress of short duration, and an attenuated N:L response can be taken as an indicator of adaptation to exercise stress.

Acute exercise effects on the immune system

PURPOSE

In recent years, health professionals have placed increased attention on the benefits of physical activity for maintaining health in the general population as well as regaining health in many disease states. Conversely, reports of apparent decreases in immune cell function after acute exercise are widespread in the literature. The purpose of this article is to evaluate critically the available data and currently employed methods, with the aim of establishing whether genuine or artefactual alterations of immune function are being reported. During and immediately after exercise, the total number of white blood cells in peripheral blood samples increases, such that the relative proportions of cell types within the leukocyte pool are altered. A number of important areas of discussion arise from these shifts in the number of circulating cells after exercise, not least of which is the artefactual effects they may have on currently employed assays of immune cell function. Recent advances in methodology are beginning to call into question the assumption that acute exercise has any genuine immunosuppressive effect.

CONCLUSION

At present, there is little evidence to suggest that the range of acute exercise intensities and durations recommended by ACSM has a major detrimental effect on the function of individual T- and B-lymphocytes, natural killer cells and neutrophils. Although individual cells may not be as adversely affected as previously supposed, it is unclear whether the numerical content of the circulating population is an important clinical consideration.

Effects of moderate altitude on exhaled nitric oxide, erythrocytes lipid peroxidation and superoxide dismutase levels

The purpose of this study was to investigate the effects of staying at a moderate altitude (2,300 m, 7 d) on the levels of plasma nitrite, exhaled nitric oxide (NO), malondialdehyde (MDA) and superoxide dismutase (SOD). Measurements were obtained from 9 female (mean age 18.3 +/- 2) and 9 male (mean age 19.3 +/- 3.7) cross-country volunteer skiers: before, during (1st day, 7th day) and after staying at a moderate altitude. Exhaled nitric oxide levels were measured only before and after staying at the altitude. Nitrite levels increased throughout the stay at the altitude, while MDA levels decreased. In parallel with the nitrite levels, SOD activities were also found to have increased. Exhaled NO values were decreased after the stay at the moderate altitude. These results show that altitude hypoxia causes decreased in NO levels in the lung but increased systemic NO levels in the blood due to inhibition of erythrocyte lipid peroxidation.

Endurance exercise causes interaction among stress hormones, cytokines, neutrophil dynamics, and muscle damage

We analyzed adaptation mechanisms regulating systemic inflammatory response of the stressed body by using an experimental challenge of repeated exercise bouts and accompanying muscle inflammation. Eight untrained men bicycled at 90 W for 90 min, 3 days in a row. Exercise induced peripheral neutrophilia with a leftward shift of neutrophil nucleus and neutrophil priming for oxidative activity determined by luminol-dependent chemiluminescence. Plasma growth hormone and interleukin-6 rose significantly after exercise and were closely correlated with the neutrophil responses. Serum creatine kinase and myoglobin levels as muscle damage markers rose after exercise in "delayed onset" and were closely correlated with the preceding neutrophil responses. These exercise-induced responses were strongest on day 1, but the magnitude gradually decreased with progressive daily exercise. In contrast, the magnitude of catecholamine responses to exercise sessions gradually rose, possibly suppressing neutrophil oxidative responses. These results indicate that stress-induced systemic release of bioactive substances may determine neutrophil mobilization and functional status, which then may affect local tissue damage of susceptible organs.

Exercise and cellular innate immune function

Epidemiological evidence suggests a link between the intensity of exercise and infectious and neoplastic disease. One likely way by which exercise exerts its effect on cancer and infection is by altering the function of the immune system. Cells of the innate immune system (i.e., macrophage [Mphi], natural killer [NK] cell, and polymorphonuclear neutrophils [PMN]) are first-line defenders against cancer and infectious disease by nature of their phagocytic, cytolytic, and antimicrobial properties. The purpose of this review is to define the role of cells of the innate immune system (i.e., Mphi, PMN, and NK cells) in infection and cancer, present current information regarding the effects of acute and chronic exercise on the quantification and functional activities of these cells, and briefly to discuss potential mechanisms as to how exercise affects these cells and describe how these changes may potentially affect susceptibility to infection and cancer. The effects of exercise on the number, functions, and characteristics of cells of the innate immune system are complex and are dependent several factors, including 1) the cell function or characteristic being analyzed; 2) the intensity, duration and chronicity of exercise; 3) the timing of measurement in relation to the exercise bout; 4) the dose and type of immunomodulator used to stimulate the cell in vitro or in vivo; and 5) the site of cellular origin. Further studies are needed to determine whether the exercise-induced changes in immune function alter incidence or progression of disease. Likewise, the mechanisms as to how exercise alters innate immune function are as yet unresolved.

Increased circulating cytokine receptors and ex vivo interleukin-1 receptor antagonist and interleukin-1beta production but decreased tumour necrosis factor-alpha production after a 5-km run

BACKGROUND

The purpose of this study was to examine the effect of a 5-km run on blood leucocytes, acute-phase proteins and cytokines. In addition, cytokines were measured in the supernatants from whole-blood cell cultures incubated with lipolysaccharide (LPS).

METHODS

Ten healthy, recreational trained, athletes (three women, seven men) volunteered for this investigation. Samples were drawn just before, immediately after and at 3 h, at 24 h and at 48 h after the race.

RESULTS

Exercise induced a transient leucocytosis (P = 0. 0002) and a mild acute-phase reaction with increase in plasma C-reactive protein (CRP) (P = 0.0115) but not in serum amyloid A (SAA) concentrations. Although plasma interleukin 6 (IL-6) was undetectable and soluble interleukin-1 receptor type II (IL-1sRII) remained unchanged, interleukin-1 receptor antagonist (IL-1ra) concentrations were elevated directly after the race with a further increase at 3 h (P < 0.0001). Soluble tumour necrosis factor (TNF) receptors were increased immediately after the run, but the effect was more marked for sTNFr p55 (two-fold increase; P < 0.0001) than for sTNFr p75 (1.16-fold increase; P = 00007). In cell cultures, the LPS-induced release of the inflammatory cytokines doubled for IL-1beta (P < 0.0001) and for IL-1ra (P < 0.0001). In contrast, TNF-alpha production decreased after the run, and a nadir was reached at 24 h (P < 0.0001).

CONCLUSION

These results suggest that a 5-km run elicits both the production of acute-phase mediators (leucocytosis and elevation of CRP) and anti-inflammatory counter-regulation as judged by the increase in circulating concentrations of IL-1ra, sTNFr p55, and sTNFrp75 and down-regulation of LPS-stimulated TNF-alpha production.

Influence of the level of dietary lipid intake and maximal exercise on the immune status in runners

Chronic exercise and high fat diets are associated with immune suppression. This study compares cellular immune responses at rest and after maximal exercise in runners after eating diets comprised of 17% low fat (LF), 32% medium fat (MF), and 41% high fat (HF) (4 wk each). VO2max increased significantly from the 17% to 41% fat diet. The leukocyte cell counts were significantly increased after exercise. In men, significantly higher proliferative response to phytohemagglutinin (PHA) (P < 0.004) was observed with MF diet, while response to pokeweed mitogen (PWM) was significantly decreased by MF and HF diets. The number of CD8+ (suppressor) T cells was significantly higher in men and exercise increased it significantly, while CD4+ (helper) T cells were not affected. Natural killer cells number was significantly increased 2.5 fold by exercise and with increase in dietary fat. The production of IL-2 by peripheral blood mononuclear cells was significantly higher in men (P < 0.0001) and increasing dietary fat significantly increased IL-2 production (P < 0.001). In men, exercise decreased the level of the proinflammatory cytokines (IL-1, IL-6 and TNF-alpha), whereas in women, with the exception of MF diet for IL-6, exercise had no effect. This study indicates that short, intense bouts of exercise in runners training 40 miles.wk-1 have mixed effects on the immune system. A high percentage of fat intake (41%) did not have any deleterious effects on the immune system of the well-trained runners.

Exercise, immunity and aging

In general population, many protective immune responses are impaired in old age, leading to an increased risk of infection. However, recent studies in SENIEUR subjects (healthy centenarians who are examples of successful aging) suggest that complex remodeling and reshaping of the immune system occurs with aging. An appropriate regular regimen of endurance exercise might help elderly to lead a quality of life by preserving immune function. However, very little is known regarding the interaction between exercise, aging and the immune system. Given that a number of age-related changes occur in many physiological systems which are known to alter the immune function both at rest and during exercise, it would be of value to learn the extent to which both acute and chronic exercise influence immune function in the elderly. The immune system response to exercise is multifaceted, depending on the nature of exercise. Significant interaction between the neuroendocrine and immune systems, and the role of lifestyle factors in immune function are known to occur. In theory, moderate exercise should help to reverse the adverse effects of aging upon the immune system by increasing the production of endocrine hormones which may contribute to less accumulation of autoreactive immune cells by enhancing the programmed cell death. Active elderly subjects demonstrated a significantly greater proliferative response to phytohemagglutinins (PHA) and to pokeweed mitogen (PWM), and higher rates of interleukin-2 (IL-2), interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) production. A moderate training program can enhance the resting natural killer (NK) cell function of healthy elderly people, potentially increasing resistance to both viral infections and preventing the formation of malignant cells. Recent studies have suggested that endurance training in later life is associated with a lesser age-related decline in certain aspects of circulating T cell function and related cytokine production. It is important that the dose of physical activity needed to optimize immune function be defined more clearly at various points during the aging process both in females and males in order to optimize the immune function and to prevent any rise in adverse effects of exercise on the elderly population.

Oxidative stress associated with exercise, psychological stress and life-style factors

Oxidative stress is a cellular or physiological condition of elevated concentrations of reactive oxygen species that cause molecular damage to vital structures and functions. Several factors influence the susceptibility to oxidative stress by affecting the antioxidant status or free oxygen radical generation. Here, we review the effect of alcohol, air pollution, cigarette smoke, diet, exercise, non-ionizing radiation (UV and microwaves) and psychological stress on the development of oxidative stress. Regular exercise and carbohydrate-rich diets seem to increase the resistance against oxidative stress. Air pollution, alcohol, cigarette smoke, non-ionizing radiation and psychological stress seem to increase oxidative stress. Alcohol in lower doses may act as an antioxidant on low density lipoproteins and thereby have an anti-atherosclerotic property.

Blood transfusion for haemolytic disease as a cause of leukocytosis in the fetus

We evaluated the effect of fetal intravascular transfusion (IVT) of leukocyte-poor red blood cells to correct fetal anaemia due to haemolytic disease on the fetal leukocyte count in 153 patients. Initial, mid-transfusion, and closing haematological studies were obtained when possible. The effect on leukocyte subsets was evaluated by the manual differential count. Fetal leukocyte count increased an average of 18.0 per cent during all IVTs (P < 0.01), despite the dilutional effect of the transfusion. The degree of leukocytosis increased with subsequent transfusions. The smallest (10.1 per cent) change occurred during the initial transfusion. A 41.8 per cent increase was noted during the sixth procedure. There was no relation between leukocytosis and gestational age, volume of transfusion, changes in umbilical vein pressure, or hydrops. Forty-two per cent of the increase was due to expansion of the neutrophil pool and 22 per cent was due to expansion of the monocyte pool. The neutrophil count increased 29 per cent (P < 0.01) and monocytes increased 64.7 per cent (P < 0.001). There was no change in eosinophil and lymphocyte counts. Both an immune aetiology and an effect of inflammatory agents may contribute to this leukocytosis.

Impact of physical activity and sport on the immune system

This review describes how exercise and physical training affect the immune system. Although many immune functions are stimulated by moderate physical activity, more vigorous effort and periods of heavy training suppress various immune response parameters. Experimental studies from our own laboratories and elsewhere illustrate that cellular infiltration of the active muscle is accompanied by phagocyte activation, suppressed NK-cell function, impaired lymphocyte proliferation, decreased in-vitro immunoglobulin production, pro-inflammatory eicosanoid release, cytokine cascade activation, and altered expression of cytokine receptors. Examples cover deliberate heavy training; single bouts of fatiguing, submaximal work; repeated bouts of exercise; and ultra-long distance athletic events. In young adults, age, environment, and light physical training do not change immune-response parameters. Parallels between immune impairment after vigorous exercise and reactions to surgical sepsis are noted. Vigorous exercise probably induces subclinical muscle injury and an associated inflammatory response. Heavy exercise may be a useful experimental model for developing more effective treatments for sepsis. For protection average athletes may take the anti-oxidant vitamins C and E and non-steroidal inflammatory drugs, if the muscles show signs of an inflammatory reaction. Top-level athletes have received immunoglobulin preparations.

The effects of plasma cortisol elevation on total and differential leukocyte counts in response to heavy-resistance exercise

The purpose of this study was to examine the impact of heavy-resistance exercise-induced elevations of plasma cortisol on circulating leukocyte counts. Nine healthy, recreationally weight-trained men volunteered for this investigation. Two exercise protocols were employed. Protocol 1 (P-1) consisted of eight sets of ten-repetition maximum leg-press exercise with 1-min rest periods between sets. Protocol 2 (P-2) was identical except for 3-min rest periods. A non-exercise protocol was used as a control treatment (C). Venous blood samples, heart rates and ratings of perceived exertion were obtained pre-, mid- and 5 min post-exercise. In order to examine the maximal influence of cortisol on leukocyte counts, we placed the subject's highest magnitude of cortisol change in response to one of the heavy-resistance exercise protocols in what we designated as the response protocol (R) and the other value was placed into what was designated as the non-response protocol (NR) for analysis. Significant increases in cortisol occurred from pre- to post-exercise for P-1 [mean (SD) 241.4 (25.0) to 302.0 (60.0)nmol . 1(-1)] and in the R conditions pre- to mid- and pre- to post-exercise [218.0(0.0) to 302.4 (37.1) to 326.8 (51.9)nmol . 1(-1)]. No significant changes in cortisol occurred for P-2, NR or the control conditions. Significant increases in total leukocyte counts occurred from pre- to mid- and pre- to post-exercise both for R [5.6 (0.4) to 7.4 (0.3) to 7.3 (0.3) cells . 10(9) . 1(-1)] and NR [5.7 (0.3) to 6.9 (0.4) to 7.1(0.4) cells . 10(9) . l(-1)]. No significant changes in differential leukocyte counts occurred. In addition, no significant correlations between cortisol and total or differential leukocyte counts were observed. These data indicate that acute increases in total leukocytes along with no changes in differential leukocyte counts can occur in response to heavy-resistance exercise that does not significantly elevate plasma cortisol concentrations.

Leucocytosis as a marker of organ damage induced by chronic strenuous physical exercise

The effects of strenuous physical exercise on the serial changes in the haematological, biochemical and hormonal markers were investigated. A group of 14 soldiers, aged 24-36 years, took part in a military training course for about 13 weeks. After severe exercise stress, an increase (90%) in the number of peripheral blood leucocytes was observed. The degree of leucocytosis showed a close correlation with the values of some serum parameters, such as concentrations of aspartate aminotransferase (AST; r = 0.747), lactate dehydrogenase (LD; r = 0.748), blood urea nitrogen (r = 0.756), creatine kinase (CK; r = 0.637), manganese-superoxide dismutase (Mn-SOD; r = 0.508), alanine aminotransferase (ALT; r = 0.542) and uric acid (r = 0.538), and concentrations of urinary parameters, such as vanilmandelic acid (r = 0.429) and free cortisol (r = 0.437). The subjects showing prominent leucocytosis over 9500 cells.microliters-1 exhibited a lower concentration of serum cholinesterase than those who showed milder leucocytosis. The serum Mn-SOD concentration was closely correlated with the serial changes in serum concentrations of AST, ALT, LD and CK, indicating exercise-induced muscle and liver damage. The change in peripheral leucocyte number was assumed to be diagnostically informative and may be a prognostic marker, reflecting organ damage and restoration after strenuous physical exercise.

Exercise-induced changes in the expression of surface adhesion molecules on circulating granulocytes and lymphocytes subpopulations

This study examined the relationship between exercise-induced changes in the concentration of circulating immunocompetent cells and their surface expression of adhesion molecules: L-selectin (CD62L) and three beta 2-integrins [LFA-1(CD11a/CD18), Mac-1 (CD11b/CD18), and p150/95(CD11c/CD18)]. Eight young male volunteers exercised on a cycle ergometer for 60 min at 60% maximal oxygen uptake. Peripheral blood samples, collected every 30 min throughout exercise and during the 2-h recovery period, were used for flow-cytometric analysis. The experimental results were compared with control data obtained ever 60 min at corresponding times of the nonexercise day. The exercise regimen induced a granulocytosis and a lymphocytosis, mainly due to an elevation of CD8+ and CD16+ cells. During recovery, a further granulocytosis occurred but accompanied by a lymphopenia. The increased CD8+ cell-count during exercise was characterized by a selective mobilization of the CD62L- and CD11ahigh cells, i.e. primed CD8+ cells. A postexercise suppression of CD4+ cell-count was derived only from CD62L+ cells. The CD11b+ and CD11c+ lymphocytes also increased during exercise, largely attributable to an increase in CD16+ cells which co-expressed CD11b and CD11c molecules. The CD62L surface density of granulocytes increased significantly during recovery. This resulted from a selective influx of CD62Lhigh granulocytes into the circulation. There were no significant changes in per-cell density of the three beta 2-integrins on granulocytes and lymphocytes throughout the experimental period. These results suggest that the cell-surface expression of CD62L (and CD11a) molecules is associated with the differential mobilization of CD8+ cells during exercise, the postexercise suppression of CD4+ cell-counts and the granulocytosis following exercise.

Are similar inflammatory factors involved in strenuous exercise and sepsis?

An increasing body of data suggest that strenuous exercise triggers an inflammatory response having some similarity with those occurring in sepsis. Indices of this inflammatory response to exercise (IRE) especially include leukocytosis, release of inflammatory mediators and acute phase reactants, tissue damage, priming of various white blood cell lines, production of free radicals; activation of complement, coagulation and fibrinolytic cascades. Inflammatory responses to strenuous exercise and sepsis could in part be due to the release of endotoxin in blood as common triggering factor, but it seems that tissue damage and/or contact system activation are more important triggering mechanisms in exercising subjects. While the magnitude and duration of cellular and humoral changes associated with IRE are quite different from those observed in sepsis, recent human studies suggested that chronic and/or excessive IRE could have adverse effects. Among the possible consequences of acute and chronic IRE are delayed onset muscular soreness and loss of force, cardiovascular complications, intravascular hemolysis, hypoferraemia and increased susceptibility to infection.