Exercise suppresses macrophage antigen presentation

Chronic Aerobic Training at Different Volumes in the Modulation of Macrophage Function and in vivo Infection of BALB/c Mice by Leishmania major

Physical inactivity is one of the main causes of chronic diseases; however, strenuous exercise can induce immunosuppression. Several studies suggest that moderate amounts of exercise lead to a Th1 response, favoring the resolution of infections caused by intracellular microorganisms, while high volumes of exercise tend to direct the response to Th2, favoring infection by them. Leishmaniasis is a parasitic disease promoted by parasites of the Leishmania genus, with clinical manifestations that vary according to the species of the parasite and the immune response of the host. The experimental Leishmania major–BALB/C mouse model provides a good model for the resistance (Th1 response) or susceptibility (Th2 response) that determines the progression of this infection. The aim of this study was to evaluate the effect of aerobic training at different volumes on modulation of in vitro macrophage infection by L. major, as well as to assess the effect of high volume (HV) aerobic training on the development of L. major in vivo in BALB/c mice. Uninfected animals were submitted to various exercise volumes: none (SED), light (LV), moderate (MV), high (HV), very high (VHV), and tapering (TAP). The macrophages of these animals were infected by L. major and the LV and MV groups showed a decrease in the infection factor, while the VHV showed an increase in the infection factor, when treated with LPS. The cytokine concentration pattern measured in the supernatants of these macrophages suggested a predominant Th1 response profile in the LV and MV groups, while the Th2 profile predominated in the VHV and TAP groups. Groups of BALB/C mice infected with L. major were subjected to high volume (iHV) or non-periodized high volume (iNPHV) exercise or kept sedentary (iSED). The exercised animals suffered a significant increase in injuries caused by the parasites. The animals in the group submitted to high volume exercise (iHV) showed visceralization of the infection. These data strongly suggest that a very high volume of aerobic training increased the susceptibility of BALB/C mice to L. major infection, while moderate distribution of training loads promoted immunological balance, better controlling the infection by this parasite.

Hypochlorous acid-modified human serum albumin suppresses MHC class II - dependent antigen presentation in pro-inflammatory macrophages

Macrophages are innate immune cells that internalize and present exogenous antigens to T cells via MHC class II proteins. They operate at sites of infection in a highly inflammatory environment, generated in part by reactive oxygen species, in particular the strong oxidant hypochlorous acid (HOCl) produced in the neutrophil respiratory burst. HOCl effectively kills a broad range of pathogens but can also contribute to host tissue damage at sites of inflammation. To prevent tissue injury, HOCl is scavenged by human serum albumin (HSA) and other plasma proteins in interstitial fluids, leading to the formation of variously modified advanced oxidation products (AOPPs) with pro-inflammatory properties. Previously, we showed that HOCl-mediated N-chlorination converts HSA and other plasma proteins into efficient activators of the phagocyte respiratory burst, but the role of these AOPPs in antigen presentation by macrophages remained unclear. Here, we show that physiologically relevant amounts of N-chlorinated HSA can strongly impair the capacity of THP-1-derived macrophages to present antigens to antigen-specific T cells via MHC class II proteins at multiple stages. Initially, N-chlorinated HSA inhibits antigen internalization by converting antigens into scavenger receptor (SR) ligands and competing with the modified antigens for binding to SR CD36. Later steps of antigen presentation, such as intracellular antigen processing and MHC class II expression are negatively affected, as well. We propose that impaired processing of pathogens or exogenous antigens by immune cells at an initial stage of infection prevents antigen presentation in an environment potentially hostile to cells of the adaptive immune response, possibly shifting it towards locations removed from the actual insult, like the lymph nodes. On the flip side, excessive retardation or complete inhibition of antigen presentation by N-chlorinated plasma proteins could contribute to chronic infection and inflammation.

Does exercise during pregnancy impact organs or structures of the maternal-fetal interface?

Exercise during pregnancy has been shown to be associated with improved health outcomes both during and after pregnancy for mother and fetus across the lifespan. Increasing physical activity and reducing sedentary behaviour during pregnancy have been recommended by many researchers and clinicians-alike. It is thought that the placenta plays a central role in mediating any positive or negative pregnancy outcomes. The positive outcomes obtained through prenatal exercise are postulated to result from exercise-induced regulation of maternal physiology and placental development. Considerable research has been performed to understand the placenta's role in pregnancy-related diseases, such as preeclampsia, fetal growth restriction, and gestational diabetes mellitus. However, little research has examined the potential for healthy lifestyle and behavioural changes to improve placental growth, development, and function. While the placenta represents the critical maternal-fetal interface responsible for all gas, nutrient, and waste exchange between the mother and fetus, the impact of exercise during pregnancy on placental biology and function is not well known. This review will focus on prenatal exercise and its promising influence on the structures of the maternal-fetal interface, with particular emphasis on the placenta. Potential molecular mechanistic hypotheses are presented to aid future investigations of prenatal exercise and placental health.

Coronavirus disease-2019: A tocsin to our aging, unfit, corpulent, and immunodeficient society

Acute and chronic respiratory illnesses cause widespread morbidity and mortality, and this class of illness now includes the novel coronavirus severe acute respiratory syndrome that is causing coronavirus disease-2019 (COVID-19). The world is experiencing a major demographic shift toward an older, obese, and physically inactive populace. Risk factor assessments based on pandemic data indicate that those at higher risk for severe illness from COVID-19 include older males, and people of all ages with obesity and related comorbidities such as hypertension and type 2 diabetes. Aging in and of itself leads to negative changes in innate and adaptive immunity, a process termed immunosenescence. Obesity causes systemic inflammation and adversely impacts immune function and host defense in a way that patterns immunosenescence. Two primary prevention strategies to reduce the risk for COVID-19 at both the community and individual levels include mitigation activities and the adoption of lifestyle practices consistent with good immune health. Animal and human studies support the idea that, in contrast to high exercise workloads, regular moderate-intensity physical activity improves immunosurveillance against pathogens and reduces morbidity and mortality from viral infection and respiratory illnesses including the common cold, pneumonia, and influenza. The odds are high that infectious disease pandemics spawned by novel pathogens will continue to inflict morbidity and mortality as the world's population becomes older and more obese. COVID-19 is indeed a wake-up call, a tocsin, to the world that primary prevention countermeasures focused on health behaviors and hygiene demand our full attention and support.

Exercise Regulates the Immune System

The profound effect of exercise on the normal functioning of the immune system has been well-known. Exercise and immune regulation are interrelated and affect each other. Exercise changes immune regulation by affecting leucocytes, red blood cells, and cytokines, etc. Regular exercise could reduce the risk of chronic metabolic and cardiorespiratory diseases, partially by the anti-inflammatory effects of exercise. However, these effects are also likely to be responsible for the suppressed immunity that make our bodies more susceptible to infections. Here we summarize the known mechanisms by which exercise-both acute and chronic-exerts its immune regulation effects.

Exercise, Immunity, and Illness

It is generally accepted that moderate amounts of exercise improve immune system functions and hence reduce the risk of infection whereas athletes engaged in regular prolonged and/or intensive training have a higher than “normal” incidence of minor infections, especially of the upper respiratory tract (URT, e.g., common cold and influenza). This is likely related to regular acute (and possibly chronic) periods of exercise-induced changes in immune function. URT infections can compromise performance directly if suffered shortly before or during competition or indirectly if suffered at other times via effects on training and/or physiological adaptations. This chapter covers the effects of exercise (acute and chronic), both positive and negative, on immune function and consequent infection risk, and considers the current state-of-the-art for monitoring and assessing this in athletes.

Effects of lentinan on the function of phagocyte in long-term heavy-duty exercising mice

Excessive exercise can lead to decreased immune function of phagocytes. This study used 50 male Kunming mice aged 40 days to evaluate the effects of lentinan (LNT) on the number of functional blood cells, the phagocytosis, peripheral blood neutrophils, and peritoneal macrophages of long-term heavy-duty exercising mice. The mice were subjected to 45 min of 5% load weight swimming training for 4 weeks, 6 times per week. Different doses of LNT were administered in the HL + T group (400 mg/kg/day), ML + T group (200 mg/kg/day), LL + T group (100 mg/kg/day), and S + T group (saline only) during the 4 weeks of excessive exercise. The phagocytic function of mice in each group was measured after long-term heavy-load exercise. The results showed that the number of white blood cells decreased significantly; the number of neutrophils and the phagocytic index of blood neutrophils in mice were significantly decreased at the end of the exercise. The macrophage phagocytosis index also decreased significantly on the fourth day after the end of the exercise. The difference was significant, and the difference in the phagocytosis rate was not obvious. The numbers of white blood cells in ML + T and HL + T groups were significantly higher than that in S + T and LL + T groups. The number of neutrophils in the ML + T and HL + T groups was significantly higher than that in the S + T and LL + T groups. The phagocytic rate and phagocytic index of neutrophils in the HL + T group were also significantly higher than those in the S + T group. The macrophage phagocytosis rate of ML + T and LL + T mice was significantly higher than that of S + T, and the phagocytic index difference was not significant. Four weeks of heavy-load exercise resulted in a decrease in phagocytic immune function in mice. Excessive exercise while feeding on LNT can improve the immune function of mice phagocytic cells. There was a positive correlation between the effect of LNT on the function of phagocytes and the LNT dose.

Exercise enhances wound healing and prevents cancer progression during aging by targeting macrophage polarity

Physical activity, which can include regular and repetitive exercise training, has been shown to decrease the incidence of age-related diseases. Aging is characterized by aberrant immune responses, including impaired wound healing and increased cancer risk. The behavior and polarized phenotype of tissue macrophages are distinct between young and old organisms. The balance of M1 and M2 macrophages is altered in the aged tissue microenvironment, with a tilt towards an M2-dominant macrophage population, as well as its associated signaling pathways. These M2-type responses may result in unresolved inflammation and create an environment that impairs wound healing and is favorable for cancer growth. We discuss the concept that exercise training can improve the regulation of macrophage polarization and normalize the inflammatory process, and thereby exert anticancer effects and enhance wound healing in older humans.

Cellular and molecular mechanisms of immunomodulation in the brain through environmental enrichment

Recent studies on environmental enrichment (EE) have shown cytokines, cellular immune components [e.g., T lymphocytes, natural killer (NK) cells], and glial cells in causal relationship to EE in bringing out changes to neurobiology and behavior. The purpose of this review is to evaluate these neuroimmune mechanisms associated with neurobiological and behavioral changes in response to different EE methods. We systematically reviewed common research databases. After applying all inclusion and exclusion criteria, 328 articles remained for this review. Physical exercise (PE), a form of EE, elicits anti-inflammatory and neuromodulatory effects through interaction with several immune pathways including interleukin (IL)-6 secretion from muscle fibers, reduced expression of Toll-like receptors on monocytes and macrophages, reduced secretion of adipokines, modulation of hippocampal T cells, priming of microglia, and upregulation of mitogen-activated protein kinase phosphatase-1 in central nervous system. In contrast, immunomodulatory roles of other enrichment methods are not studied extensively. Nonetheless, studies showing reduction in the expression of IL-1β and tumor necrosis factor-α in response to enrichment with novel objects and accessories suggest anti-inflammatory effects of novel environment. Likewise, social enrichment, though considered a necessity for healthy behavior, results in immunosuppression in socially defeated animals. This has been attributed to reduction in T lymphocytes, NK cells and IL-10 in subordinate animals. EE through sensory stimuli has been investigated to a lesser extent and the effect on immune factors has not been evaluated yet. Discovery of this multidimensional relationship between immune system, brain functioning, and EE has paved a way toward formulating environ-immuno therapies for treating psychiatric illnesses with minimal use of pharmacotherapy. While the immunomodulatory role of PE has been evaluated extensively, more research is required to investigate neuroimmune changes associated with other enrichment methods.

Allergy and sports in children

Physical activity is beneficial for children with positive outcomes for mental and physical well-being. Allergic conditions unique to the sporting arena may serve as an impediment to participation in physical activity for allergic children. A common example is exercise-induced asthma; less common activity-related allergic conditions include food-dependent exercise-induced anaphylaxis, exercise-induced anaphylaxis, and exercise-induced urticaria. Allergic children may also be at risk of allergic reactions when exposed to allergens that are more commonly found in the sports environment, e.g., latex, sports drinks, and medications such as NSAIDs. Recent advances in our understanding of the patho-physiological and immunologic mechanisms that may account for these conditions have facilitated more effective and safer management strategies. There are also important immunologic lessons to be learnt with respect to specific physical factors that may result in diminished allergen tolerance; indeed, these lessons may facilitate safer allergen desensitisation regimens. The role of the immune system in exercise-induced immunoallergic syndromes, clinical aspects, and diagnostic and therapeutic approaches are discussed in this review.

Exhaustive exercise reduces TNF-α and IFN-α production in response to R-848 via toll-like receptor 7 in mice

Stressful exercise results in temporary immune depression. However, the impact of exercise on the immune responses via toll-like receptor (TLR) 7, which recognizes the common viral genomic feature, single-stranded RNA, remains unclear. To clarify the effect of stressful exercise on immune function in response to viral infection, we measured the changes in the plasma concentration of tumor necrosis factor (TNF)-α and interferon (IFN)-α, which are induced downstream from the TLR–ligand interaction, in exhaustive-exercised mice immediately after treatment with the imidazoquinoline R-848, which can bind to and activate TLR7. Both exhaustive-exercised (EX) and non-exercised (N-EX) male C3H/HeN mice were injected with R-848 (5 mg kg⁻¹), and blood samples were collected. In addition, RAW264 cells, which are mouse macrophage cells, were cultured 30 min after epinephrine (10 μM) or norepinephrine (10 μM) treatments, and were then stimulated with R-848 (10 μg ml⁻¹). In addition, the effect of propranolol (10 mg kg⁻¹) as blockade of β-adrenergic receptors on R-848-induced TNF-α and IFN-α production in the exercised mice was examined. Both the TNF-α and IFN-α concentrations in the plasma of EX were significantly lower than those in the plasma of N-EX after R-848 injection (P < 0.05 and P < 0.01, respectively), although the R-848 treatment increased the plasma TNF-α and IFN-α concentrations in both groups (P < 0.01, respectively). The R-848-induced TNF-α production in RAW264 cells was significantly inhibited by epinephrine and norepinephrine pre-treatment, although IFN-α was not detected. The propranolol treatment completely inhibited exercise-induced TNF-α and IFN-α suppression in response to R-848 in the mice. These data suggest that EX induces a reduction in TNF-α and IFN-α production in response to R-848, and that these phenomena might be regulated by an exercise-induced elevation of the systemic catecholamines.

Physical activity, immunity and infection

During the last few decades, scientific evidence has confirmed a wide range of health benefits related to regular physical activity. How physical activity affects the immune function and infection risk is, however, still under debate. Commonly, intensive exercise suppresses the activity and levels of several immune cells, while other immune functions may be stimulated by moderate physical activity. With this knowledge, the understanding of the relationship between different levels of physical activity on the immune function has been raised as a potential tool to protect health not only in athletes but also in the general population; the mechanisms that translate a physically active lifestyle into good health continue to be investigated. Reviewing the literature, although several outcomes (i.e. the mechanisms by which different levels and duration of physical activity programmes affect numerous cell types and responses) remain unclear, given that the additional benefits encompass healthy habits including exercise, the use of physical activity programmes may result in improved health of elderly populations. Moderate physical activity or moderate-regulated training may enhance the immune function mainly in less fit subjects or sedentary population and the pre-event fitness status also seems to be an important individual factor regarding this relationship. Although adequate nutrition and regular physical activity habits may synergistically improve health, clinical trials in athletes using nutritional supplements to counteract the immune suppression have been inconclusive so far.Further research is necessary to find out to what extent physical activity training can exert an effect on the immune function.

Exercise stress increases susceptibility to influenza infection

Exercise stress is associated with an increased risk for upper respiratory tract infection (URTI) while moderate exercise has been associated with a decreased risk. We have shown that exercise stress can increase susceptibility (morbidity, symptom severity and mortality) to HSV-1 respiratory infection, but there is little evidence on the effects of stressful exercise on susceptibility to the principal etiological agents of human respiratory infections, including influenza viruses. This study examined the effects of stressful exercise on susceptibility to influenza virus (A/Puerto Rico/8/34 (H1N1)). Mice were assigned to one of two groups: exercise (Ex) or control (Con). Exercise consisted of a treadmill run to volitional fatigue ( approximately 120 min) performed on three consecutive days. Fifteen minutes after the last bout of exercise or rest, mice (n=20-21/group) were intranasally inoculated with a standardized dose of influenza virus (0.25 HAU). Mice were monitored daily for morbidity (time to sickness), symptom severity and mortality (time to death) for 21 days. Exercise stress was associated with an increase in susceptibility to infection (morbidity, mortality and symptom severity on days 6 and 7; P<0.05). These data from a controlled influenza virus challenge model add significantly to the growing body of evidence that severe exercise can increase susceptibility to URTI.

Benefits of oat beta-glucan on respiratory infection following exercise stress: role of lung macrophages

Exercise stress is associated with an increased risk for upper respiratory tract infection (URTI). We have shown that consumption of the soluble oat fiber beta-glucan (ObetaG) can offset the increased risk for infection and decreased macrophage antiviral resistance following stressful exercise; however, the direct role of macrophages is unknown. This study examined the effect of macrophage depletion on the benefits of orally administered ObetaG on susceptibility to infection (morbidity, symptom severity, and mortality) following exercise stress. CL(2)MDP (Ex- H(2)O-CL(2)MDP, Ex-ObetaG-CL(2)MDP, Con-H(2)O-CL(2)MDP, Con-ObetaG-CL(2)MDP)-encapsulated liposomes were administered intranasally to deplete macrophages, and PBS (Ex-H(2)O-PBS, Ex-ObetaG-PBS, Con-H(2)O-PBS, Con-ObetaG-PBS)-encapsulated liposomes were given to macrophage-intact groups. Ex mice ran to volitional fatigue on a treadmill for 3 consecutive days, and ObetaG mice were fed a solution of 50% ObetaG in their drinking water for 10 consecutive days before infection. Fifteen minutes following the final bout of Ex or rest, mice were intranasally inoculated with 50 microl of a standardized dose of herpes simplex virus-1. Ex increased morbidity (P < 0.001) and symptom severity (P < 0.05) but not mortality (P = 0.09). The increase in morbidity and symptom severity was blocked by ObetaG consumption for 10 consecutive days before exercise and infection [morbidity (P < 0.001) and symptom severity (P < 0.05)]. Depletion of macrophages negated the beneficial effects of ObetaG on reducing susceptibility to infection following exercise stress, as evidenced by an increase in morbidity (P < 0.01) and symptom severity (P < 0.05). Results indicate that lung macrophages are at least partially responsible for mediating the beneficial effects of ObetaG on susceptibility to respiratory infection following exercise stress.

Phagocytosis of cholesteryl ester is amplified in diabetic mouse macrophages and is largely mediated by CD36 and SR-A

Type 2 diabetes (T2D) is associated with accelerated atherosclerosis, which accounts for approximately 75% of all diabetes-related deaths. Here we investigate the link between diabetes and macrophage cholesteryl ester accumulation. When diabetic (db/db) mice are given cholesteryl ester intraperitoneally (IP), peritoneal macrophages (PerMΦs) recovered from these animals showed a 58% increase in intracellular cholesteryl ester accumulation over PerMΦs from heterozygote control (db/+) mice. Notably, PerMΦ fluid-phase endocytosis and large particle phagocytosis was equivalent in db/+and db/db mice. However, IP administration of CD36 and SR-A blocking antibodies led to 37% and 25% reductions in cholesteryl ester accumulation in PerMΦ. Finally, in order to determine if these scavenger receptors (SRs) were part of the mechanism responsible for the increased accumulation of cholesteryl esters observed in the diabetic mouse macrophages, receptor expression was quantified by flow cytometry. Importantly, db/db PerMΦs showed a 43% increase in CD36 expression and an 80% increase in SR-A expression. Taken together, these data indicate that direct cholesteryl ester accumulation in mouse macrophages is mediated by CD36 and SR-A, and the magnitude of accumulation is increased in db/db macrophages due to increased scavenger receptor expression.

Markers to measure immunomodulation in human nutrition intervention studies

Normal functioning of the immune system is crucial to the health of man, and diet is one of the major exogenous factors modulating individual immunocompetence. Recently, nutrition research has focused on the role of foods or specific food components in enhancing immune system responsiveness to challenges and thereby improving health and reducing disease risks. Assessing diet-induced changes of immune function, however, requires a thorough methodological approach targeting a large spectrum of immune system parameters. Currently, no single marker is available to predict the outcome of a dietary intervention on the resistance to infection or to other immune system-related diseases. The present review summarises the immune function assays commonly used as markers in human intervention studies and evaluates their biological relevance (e.g. known correlation with clinically relevant endpoints), sensitivity (e.g. within- and between-subject variation), and practical feasibility. Based on these criteria markers were classified into three categories with high, medium or low suitability. Vaccine-specific serum antibody production, delayed-type hypersensitivity response, vaccine-specific or total secretory IgA in saliva and the response to attenuated pathogens, were classified as markers with high suitability. Markers with medium suitability include natural killer cell cytotoxicity, oxidative burst of phagocytes, lymphocyte proliferation and the cytokine pattern produced by activated immune cells. Since no single marker allows conclusions to be drawn about the modulation of the whole immune system, except for the clinical outcome of infection itself, combining markers with high and medium suitability is currently the best approach to measure immunomodulation in human nutrition intervention studies. It would be valuable to include several immune markers in addition to clinical outcome in future clinical trials in this area, as there is too little evidence that correlates markers with global health improvement.

Augmented Lipopolysaccharide-Induced TNF-α Production by Peritoneal Macrophages in Type 2 Diabetic Mice Is Dependent on Elevated Glucose and Requires p38 MAPK

Dysregulated inflammation is a complication of type 2 diabetes (T2D). In this study, we show that augmented LPS-induced TNF-alpha production by resident peritoneal macrophages (PerMphi) in type 2 diabetic (db/db) mice is dependent on elevated glucose and requires p38 MAPK. Intraperitoneal LPS administered to db/db and nondiabetic (db/+) mice induced 3- and 4-fold more TNF-alpha in the peritoneum and serum, respectively, of db/db mice as compared with db/+ mice. Examination of the TLR-4/MD2 complex and CD14 expression showed no difference between db/db and db/+ PerMphi. Ex vivo stimulation of PerMphi with LPS produced a similar 3-fold increase in TNF-alpha production in db/db PerMphi when compared with db/+ PerMphi. PerMphi isolated from db/+ mice incubated in high glucose (4 g/L) medium for 12 h produced nearly 2-fold more TNF-alpha in response to LPS than PerMphi incubated in normal glucose medium (1 g/L). LPS-dependent stimulation of PI3K activity, ERK1/2 activation, and p38 kinase activity was greater in PerMphi from db/db mice as compared with db/+ mice. Only inhibition of p38 kinase blocked LPS-induced TNF-alpha production in PerMphi from db/db mice. Taken together, these data indicate that augmented TNF-alpha production induced by LPS in macrophages during diabetes is due to hyperglycemia and increased LPS-dependent activation of p38 kinase.

Gender Differences in Macrophage Antiviral Function following Exercise Stress

INTRODUCTION

In male mice, exhaustive exercise increases susceptibility to respiratory infection following intranasal inoculation with herpes simplex virus-1 (HSV-1), whereas moderate exercise decreases the risk of infection. These responses have been linked with altered macrophage antiviral resistance, among other immune mechanisms. Female mice appear to be better protected from death than male mice following HSV-1 infection, although their response to exercise stress is similar. The possible immune mechanisms, however, have not been explored.

PURPOSE

This study was conducted to examine gender differences in macrophage antiviral resistance following repeated moderate and exhaustive treadmill exercise.

METHODS

Male (M, N = 36) and female (F, N = 36) CD-1 mice were randomly assigned to moderate exercise (Mod), exhaustive exercise (Exh), or control (C) groups. Exercise was done daily for 3 d; moderate exercise consisted of treadmill running for 90 min, whereas exhaustive exercise consisted of running to volitional fatigue (approximately 50 min).

RESULTS

Females had greater macrophage antiviral resistance to HSV-1 than males in C and Mod (P < 0.05), but not Exh; Mod increased resistance, whereas Exh decreased resistance similarly in both genders (P < 0.001).

CONCLUSIONS

These data suggest that altered macrophage antiviral resistance to HSV-1 may contribute to gender differences in in vivo resistance to HSV-1 respiratory infection at rest, as well as following moderate and exhaustive exercise.

Influence of ultra-endurance exercise on immunoglobulin isotypes and subclasses

BACKGROUND

Strenuous exercise is associated with tissue damage. This activates the innate immune system and local inflammation. Interaction between innate and adaptive immunity is essential for maintaining health, suggesting that the adaptive immune system may also be altered by exercise.

OBJECTIVES

To determine exercise induced changes in the adaptive immune system by measuring the immunoglobulin isotype and subclass response to an ultra-marathon.

METHODS

Venepuncture was performed on 11 experienced volunteers (six men, five women; mean (SD) age 43 (9.8) years) 24 hours before the projected finishing time and immediately after and 3, 24, and 72 hours after an ultra-marathon (90 km). Serum was stored at -80 degrees C. IgM, IgD, IgA, IgG, IgG1, 2, 3, and 4, and total IgE were measured.

RESULTS

The following immunoglobulins were significantly (p< or =0.05) altered after the race: IgD, immediately (-51%) and 24 hours (-41%) after; IgM 24 hours after (-23%); total IgG immediately after (+12%). There were no reports of symptoms of upper respiratory tract infections after the ultra-marathon.

CONCLUSIONS

In experienced ultra-endurance runners, alterations in immunoglobulin concentrations after a race suggest an enhanced immune response, including isotype switching, interactions with the innate immune system, and a secondary antibody response. These alterations may have a role in the maintenance of subject health after an ultra-marathon.

IL-1beta-mediated innate immunity is amplified in the db/db mouse model of type 2 diabetes

Chronic inflammation appears to play a critical role in type 2 diabetes and its complications. Here we tested the hypothesis that this inflammatory dysregulation affects the IL-1beta system and has functional consequences in the brain. Diabetic, db/db, and nondiabetic, db/+, mice were administered i.p. LPS, a potent cytokine inducer, at a dose of 100 microg/kg/mouse. db/db mouse innate immune-associated sickness behavior was 14.8, 33, 44.7, and 34% greater than that of db/+ mice at 2, 4, 8, and 12 h, respectively. When a fixed dose of LPS was used (5 microg/mouse), db/db mouse sickness was again enhanced 18.4, 22.2, and 14.5% at 4, 8, and 12 h as compared with db/+ mice. In diabetic mice, peritoneal macrophages produced more IL-1beta in response to LPS, and peritoneal levels of IL-1beta induced by LPS were increased. Importantly, IL-1R antagonist and type 2 IL-1 receptor (IL-1R2) failed to up-regulate in response to LPS in db/db mice. Finally, both peripheral and central administration of IL-1beta, itself, induced sickness in db/db mice that mimicked the effects of peripheral LPS and was significantly greater than that seen in db/+ mice. Taken together, these results indicate that IL-1beta-mediated innate immunity is augmented in db/db mice both at the periphery and in the brain, and the mechanism is due to diabetes-associated loss of IL-1beta counterregulation.

Role of host's antitumor immunity in exercise-dependent regression of murine T-cell lymphoma

We have reported that the ascitic growth of a transplantable T cell lymphoma of spontaneous origin, designated as Dalton's lymphoma (DL), is associated with a concomitant immunosuppression. We have also reported that progressive in vivo growth of DL resulted in an inhibition of macrophage functions. In present investigation we report that physical exercise by DL-bearing mice, on a treadmill on a daily basis for various time durations for 10 days, increased the life span along with an inhibition of tumor growth. A significant decrease in the volume of ascitic fluid and number of cells in the tumor was obtained in mice, which underwent exercise. DL cells obtained from exercised groups showed a decreased proliferation in vitro. An augmentation in the percent of cells showing apoptotic morphology and percent specific DNA fragmentation was observed, suggesting that physical exercise increased the incidence of apoptosis in tumor cells. Moreover, macrophages obtained from tumor-bearing mice, which underwent exercise training, showed an augmented tumoricidal activity and production of tumoricidal molecules like interleukin-1 (IL-1), tumor necrosis factor (TNF) and nitric oxide (NO). On the basis of this study it is suggested that the regression of tumor growth consequent to physical exercise training of tumor bearing host, may be due to an exercise-dependent augmentation of macrophage tumoricidal functions.

Role of lung macrophages on susceptibility to respiratory infection following short-term moderate exercise training

Moderate exercise training is associated with a decreased risk for upper respiratory tract infection in human and animal studies, but the mechanisms have not been elucidated. Lung macrophages play an important role in resistance to respiratory infection, and moderate exercise can enhance macrophage antiviral resistance, but no studies have directly tested the role of lung macrophages in this response. This study tested the effect of lung macrophage depletion on susceptibility to infection following short-term moderate exercise training. Mice were assigned to one of four groups: exercise (Ex) and resting controls (Con) with and without clodronate encapsulated liposomes (CL2MDP-lip). Ex mice ran for 1 h on a treadmill for 6 days at 36 m/min, 8% grade. Fifteen minutes following exercise or rest on the last day of training, mice were intranasally inoculated with a standardized dose of herpes simplex virus type 1. Clodronate (Ex-CL2MDP-lip and Con-CL2MDP-lip) or PBS liposomes (Ex-PBS-lip and Con-PBS-lip) (100 μl) were intranasally administered following exercise or rest on the 4th day of training and again on the 4th day postinfection. Morbidity, mortality, and symptom severity were monitored for 21 days. Exercise decreased morbidity by 36%, mortality by 61%, and symptom severity score on days 5–7 ( P < 0.05). Depletion of lung macrophages negated the beneficial effects of moderate exercise. This was indicated by no differences between Ex-CL2MDP-lip and Con-PBS-lip in morbidity (89 vs. 95%), mortality (79 vs. 95%), or symptom severity. Results indicate that lung macrophages play an important role in mediating the beneficial effects of moderate exercise on susceptibility to respiratory infection.

Effects of Oat ??-Glucan on Innate Immunity and Infection after Exercise Stress

PURPOSE

To test the effects of oat beta-glucan (ObetaG) on respiratory infection, macrophage antiviral resistance, and NK cytotoxicity.

METHODS

Mice were randomly assigned to one of four groups: Ex-H2O, Ex-ObetaG, Con-H2O, or Con-ObetaG. ObetaG was fed in the drinking water for 10 d before intranasal inoculation of HSV-1 or sacrifice. Exercise consisted of treadmill running to volitional fatigue (approximately 140 min) for three consecutive days. Fifteen minutes after the last bout of exercise or rest, mice (N = 24) were intranasally inoculated with a standardized dose of HSV-1. Mice were monitored twice daily for morbidity and mortality. Additional mice were sacrificed after exercise, peritoneal macrophages were obtained via i.p. lavage and assayed for antiviral resistance to HSV-1 (N = 18), and spleens were harvested and assayed for NK cell cytotoxicity (N = 12).

RESULTS

Exercise stress was associated with a 28% increase in morbidity (P = 0.036) and 18% increase in mortality (P = 0.15). Ingestion of ObetaG before infection prevented this increase in morbidity (P = 0.048) and mortality (P = 0.05). Exercise stress was associated with a decrease in macrophage antiviral resistance (P = 0.007), which was blocked by ingestion of ObetaG (P < 0.001). There were no effects of exercise or ObetaG on NK cytotoxicity.

CONCLUSION

These data suggest that daily ingestion of ObetaG may offset the increased risk of URTI associated with exercise stress, which may be mediated, at least in part, by an increase in macrophage antiviral resistance.

Insulin receptor substrate-2-dependent interleukin-4 signaling in macrophages is impaired in two models of type 2 diabetes mellitus

We have shown previously that hyperinsulinemia inhibits interferon-alpha-dependent activation of phosphatidylinositol 3-kinase (PI3-kinase) through mammalian target of rapamycin (mTOR)-induced serine phosphorylation of insulin receptor substrate (IRS)-1. Here we report that chronic insulin and high glucose synergistically inhibit interleukin (IL)-4-dependent activation of PI3-kinase in macrophages via the mTOR pathway. Resident peritoneal macrophages (PerMPhis) from diabetic (db/db) mice showed a 44% reduction in IRS-2-associated PI3-kinase activity stimulated by IL-4 compared with PerMPhis from heterozygote (db/+) control mice. IRS-2 from db/db mouse PerMPhis also showed a 78% increase in Ser/Thr-Pro motif phosphorylation without a difference in IRS-2 mass. To investigate the mechanism of this PI3-kinase inhibition, 12-O-tetradecanoylphorbol-13-acetate-matured U937 cells were treated chronically with insulin (1 nm, 18 h) and high glucose (4.5 g/liter, 48 h). In these cells, IL-4-stimulated IRS-2-associated PI3-kinase activity was reduced by 37.5%. Importantly, chronic insulin or high glucose alone did not impact IL-4-activated IRS-2-associated PI3-kinase. Chronic insulin + high glucose did reduce IL-4-dependent IRS-2 tyrosine phosphorylation and p85 association by 54 and 37%, respectively, but did not effect IL-4-activated JAK/STAT signaling. When IRS-2 Ser/Thr-Pro motif phosphorylation was examined, chronic insulin + high glucose resulted in a 92% increase in IRS-2 Ser/Thr-Pro motif phosphorylation without a change in IRS-2 mass. Pretreatment of matured U937 cells with rapamycin blocked chronic insulin + high glucose-dependent IRS-2 Ser/Thr-Pro motif phosphorylation and restored IL-4-dependent IRS-2-associated PI3-kinase activity. Taken together these results indicate that IRS-2-dependent IL-4 signaling in macrophages is impaired in models of type 2 diabetes mellitus through a mechanism that relies on insulin/glucose-dependent Ser/Thr-Pro motif serine phosphorylation mediated by the mTOR pathway.

Effects of moderate exercise and oat β-glucan on innate immune function and susceptibility to respiratory infection

Both moderate exercise and the soluble oat fiber β-glucan can increase immune function and decrease risk of infection, but no information exists on their possible combined effects. This study tested the effects of moderate exercise and oat β-glucan on respiratory infection, macrophage antiviral resistance, and natural killer (NK) cell cytotoxicity. Mice were assigned to four groups: exercise and water, exercise and oat β-glucan, control water, or control oat β-glucan. Oat β-glucan was fed in the drinking water for 10 days before intranasal inoculation of herpes simplex virus type 1 (HSV-1) or euthanasia. Exercise consisted of treadmill running (1 h/day) for 6 days. Macrophage resistance to HSV-1 was increased with both exercise and oat β-glucan, whereas NK cell cytotoxicity was only increased with exercise. Exercise was also associated with a 45 and 38% decrease in morbidity and mortality, respectively. Mortality was also decreased with oat β-glucan, but this effect did not reach statistical significance. No additive effects of exercise and oat β-glucan were found. These data confirm a positive effect of both moderate exercise and oat β-glucan on immune function, but only moderate exercise was associated with a significant reduction in the risk of upper respiratory tract infection in this model.

Modulation of immune response through nutraceutical interventions: implications for canine and feline health

Mounting research demonstrates that certain nutraceutical compounds interact with the immune system. These interactions may be positive or negative depending on the compound or dose administered to the individual. Understanding the mechanisms by which these compounds work should provide opportunities to design nutritional interventions to bolster the health of dogs and cats.

Overtraining, excessive exercise, and altered immunity: is this a T helper-1 versus T helper-2 lymphocyte response?

Overtraining syndrome (OTS) occurs where an athlete is training vigorously, yet performance deteriorates. One sign of OTS is suppressed immune function, with an increased incidence of upper respiratory tract infection (URTI). An increased incidence of URTIs is also associated with high volume/intensity training, as well as with excessive exercise (EE), such as a marathon, manifesting between 3-72 hours post-race. Presently, there is no encompassing theory to explain EE and altered immune competence. Recently, it has been conclusively established that T helper lymphocytes (T(H)), a crucial aspect of immune function, represent two distinct functional subsets: T(H)1 and T(H)2 lymphocytes. T(H)1 lymphocytes are associated with cell-mediated immunity (CMI) and the killing of intracellular pathogens, while T(H)2 lymphocytes are associated with humoral immunity and antibody production. When T(H)-precursor cells are activated, the balance is tipped in favour of one or the other. Furthermore, the most appropriate means of determining the T(H)-subset, is by the prevailing cytokine 'pattern'. This paper hypothesises that exercise-related immunosuppression is due to tissue trauma sustained during intense exercise, producing cytokines, which drive the development of a T(H)2 lymphocyte profile. A T(H)2 cell response results in simultaneous suppression of CMI, rendering the athlete susceptible to infection. Additionally, increased levels of circulating stress hormones (cortisol and catecholamines), as well as prostaglandin E(2), support up-regulation of T(H)2 lymphocytes. Marathon-related data are presented to support this hypothesis. It is concluded that an increased incidence of illness associated with OTS and in response to EE is not due to immunosuppression per se, but rather to an altered focus of immune function, with an up-regulation of humoral immunity and suppression of CMI.

Special feature for the Olympics: effects of exercise on the immune system: exercise effects on systemic immunity

Heavy exertion has acute and chronic influences on systemic immunity. In the resting state, the immune systems of athletes and non-athletes are more similar than disparate with the exception of NK cell activity, which tends to be elevated in athletes. Many components of the immune system exhibit adverse change after prolonged, heavy exertion. These immune changes occur in several compartments of the immune system and body (e.g. the skin, upper respiratory tract mucosal tissue, lung, blood and muscle). Although still open to interpretation, most exercise immunologists believe that during this 'open window' of impaired immunity (which may last between 3 and 72 h, depending on the immune measure) viruses and bacteria may gain a foothold, increasing the risk of subclinical and clinical infection. The infection risk may be amplified when other factors related to immune function are present, including exposure to novel pathogens during travel, lack of sleep, severe mental stress, malnutrition or weight loss.

Special feature for the Olympics: effects of exercise on the immune system: exercise-induced modulation of macrophage function

Macrophages are important effector cells involved in phagocytosis, microbial killing and antitumour activity. Macrophages also display accessory cell function, in that they can present antigen to foster the development of T lymphocyte-mediated immunity. Recent work, including studies from this group, has demonstrated that acute and chronic exercise can affect many facets of macrophage biology. Manifestation of these effects depends on exercise intensity and duration, the function measured, the timing of measurement in relation to exercise and the concentration of the macrophage-activating stimulus. Exercise has potent stimulatory effects on phagocytosis, antitumour activity, reactive oxygen and nitrogen metabolism, and chemotaxis. Indeed, it has been shown that exercise training can increase macrophage antitumour activity in mice of different ages. However, not all functions are enhanced by exercise. Exercise-induced reductions in macrophage MHC II expression and antigen-presentation capacity have been documented. These findings bring up the possibility that exercise, and perhaps other stressors, activate macrophages for effector functions while downregulating accessory cell functions. To a large extent, the mechanisms responsible for the exercise-induced changes in macrophage function remain unknown, but may depend on exercise-induced changes in neuroendocrine factors. Future studies need to explore the effects in a mechanistic way and provide documentation as to their physiological significance.

Role for cathepsin F in invariant chain processing and major histocompatibility complex class II peptide loading by macrophages

The major histocompatibility complex (MHC) class II-associated invariant chain (Ii) regulates intracellular trafficking and peptide loading of MHC class II molecules. Such loading occurs after endosomal degradation of the invariant chain to a approximately 3-kD peptide termed CLIP (class II-associated invariant chain peptide). Cathepsins L and S have both been implicated in degradation of Ii to CLIP in thymus and peripheral lymphoid organs, respectively. However, macrophages from mice deficient in both cathepsins S and L can process Ii and load peptides onto MHC class II dimers normally. Both processes are blocked by a cysteine protease inhibitor, indicating the involvement of an additional Ii-processing enzyme(s). Comparison of cysteine proteases expressed by macrophages with those found in splenocytes and dendritic cells revealed two enzymes expressed exclusively in macrophages, cathepsins Z and F. Recombinant cathepsin Z did not generate CLIP from Ii-MHC class II complexes, whereas cathepsin F was as efficient as cathepsin S in CLIP generation. Inhibition of cathepsin F activity and MHC class II peptide loading by macrophages exhibited similar specificity and activity profiles. These experiments show that cathepsin F, in a subset of antigen presenting cells (APCs), can efficiently degrade Ii. Different APCs can thus use distinct proteases to mediate MHC class II maturation and peptide loading.

Intracellular mechanisms responsible for exercise-induced suppression of macrophage antigen presentation

In a previous study, we demonstrated that exhaustive exercise suppressed peritoneal macrophage antigen presentation (AP). In this study, we explored the intracellular mechanism(s) responsible for this suppression. Pathogen-free male BALB/c mice (8 +/- 2 wk) were randomly assigned to either home cage control (HCC) or exhaustive exercise stress (Exh, 18-30 m/min for 3 h/day) treatment groups. The mice underwent treatments for a period of 4 days during induced peritoneal thioglycollate inflammation. Elicited macrophages were harvested, purified, and incubated with chicken ovalbumin (C-Ova, 2. 5 and 10 mg/ml) for 18 h. After macrophages were washed, they were cocultured with C-Ova-specific T cells for 48 h at which time the supernates were harvested and analyzed via ELISA for interleukin (IL)-2 as an indication of macrophage AP. There was no significant (P > 0.05) difference in macrophage AP between cells fixed with paraformaldehyde vs. those that remained unfixed, suggesting that Exh did not affect production of soluble factors influencing macrophage AP (i.e., IL-1, IL-4, PGE(2)). The ability of macrophages to generate C-Ova immunogenic peptides was analyzed using FITC-labeled C-Ova, which shows fluorescence only when degraded intracellularly. There was a significant ( approximately 20%, P < 0. 05) suppression in fluorescence in the Exh compared with HCC, indicating a possible defect in the ability of macrophages from Exh to degrade C-Ova into immunogenic peptides. Macrophages were also incubated with C-Ova immunogenic peptide in a manner identical to that for native C-Ova. We found a similar suppression ( approximately 22-38%, P < 0.05) in macrophage AP using a C-Ova peptide when compared with native C-Ova in the Exh group, indicating reduced major histocompatibility complex (MHC) II loading and/or C-Ova-MHC II complex cell surface expression. In conclusion, these data indicate an intracellular defect in the macrophage antigen processing pathway induced by Exh.