Meningococcal A vaccination response is enhanced by acute stress in men

Effects of Exercise and Physical Activity Levels on Vaccination Efficacy: A Systematic Review and Meta-Analysis

Objective: We examined whether different intensities of exercise and/or physical activity (PA) levels affected and/or associated with vaccination efficacy. Methods: A systematic review and meta-analysis was conducted and registered with PROSPERO (CRD42021230108). The PubMed, EMBASE, Cochrane Library (trials), SportDiscus, and CINAHL databases were searched up to January 2022. Results: In total, 38 eligible studies were included. Chronic exercise increased influenza antibodies (standardized mean difference (SMD) = 0.49, confidence interval (CI) = 0.25−0.73, Z = 3.95, I2 = 90%, p < 0.01), which was mainly driven by aerobic exercise (SMD = 0.39, CI = 0.19−0.58, Z = 3.96, I2 = 77%, p < 0.01) as opposed to combined (aerobic + resistance; p = 0.07) or other exercise types (i.e., taiji and qigong, unspecified; p > 0.05). PA levels positively affected antibodies in response to influenza vaccination (SMD = 0.18, CI = 0.02−0.34, Z = 2.21, I2 = 76%, p = 0.03), which was mainly driven by high PA levels compared to moderate PA levels (Chi2 = 10.35, I2 = 90.3%, p < 0.01). Physically active individuals developed influenza antibodies in response to vaccination in >4 weeks (SMD = 0.64, CI = 0.30−0.98, Z = 3.72, I2 = 83%, p < 0.01) as opposed to <4 weeks (p > 0.05; Chi2 = 13.40, I2 = 92.5%, p < 0.01) post vaccination. Conclusion: Chronic aerobic exercise or high PA levels increased influenza antibodies in humans more than vaccinated individuals with no participation in exercise/PA. The evidence regarding the effects of exercise/PA levels on antibodies in response to vaccines other than influenza is extremely limited.

Exercise after influenza or COVID-19 vaccination increases serum antibody without an increase in side effects

Vaccination is an effective public health measure, yet vaccine efficacy varies across different populations. Adjuvants improve vaccine efficacy but often increase reactogenicity. An unconventional behavioral "adjuvant" is physical exercise at the time of vaccination. Here, in separate experiments, we examined the effect of 90-minute light- to moderate-intensity cycle ergometer or outdoor walk/jog aerobic exercise performed once after immunization on serum antibody response to three different vaccines (2009 pandemic influenza H1N1, seasonal influenza, and COVID-19). Exercise took place after influenza vaccination or after the first dose of Pfizer-BioNTech COVID-19 vaccine. A mouse model of influenza A immunization was used to examine the effect of exercise on antibody response and the role of IFNα as a potential mechanism by treating mice with anti-IFNα antibody. The results show that 90 min of exercise consistently increased serum antibody to each vaccine four weeks post-immunization, and IFNα may partially contribute to the exercise-related benefit. Exercise did not increase side effects after the COVID-19 vaccination. These findings suggest that adults who exercise regularly may increase antibody response to influenza or COVID-19 vaccine by performing a single session of light- to moderate-intensity exercise post-immunization.

Analgesic and adjuvant properties of exercise with vaccinations in healthy young population

Introduction: Exercise holds the potential to be beneficial if used during vaccination processes by 1)exercise-induced analgesia to reduce pain associated with vaccination, 2)immune-enhancing effects, improving antibody responses to the vaccine, and 3)reducing local and systemic adverse reactions to the vaccine. This study examines whether analgesic responses could be enhanced locally in the exercising limb to further benefit the use of exercise during influenza vaccination processes to minimize vaccine-related pain and improve antibody response to inactivated influenza vaccines.Methods: 57 participants (22.6 ± 3.2 years, 33 females) randomized into a control (n = 19) or one of two exercise groups: pre-vaccine arm (n = 19) or pre-vaccine leg (n = 19). Intervention groups performed exercise (15 minutes), prior to administration of the vaccine. Vaccine-related pain and pressure pain threshold (PPT) were measured at baseline and post-vaccination for all groups. Blood samples were taken on the day of vaccination and one month later to measure serum antibody titers to influenza.Results: No significant difference in vaccine-related pain or change in PPT was found with exercise, however, there was a trend in higher reports of vaccine-related pain in females compared to males(p = .06). Significantly higher fold increase (p = .02) of the B/Brisbane/60/2008 strain was found in the exercise group compared to the control group.Conclusion: The current study failed to observe an analgesic effect of exercise to improve vaccine-related pain in young adults. However, immune-enhancing effects in one of four strains suggest potential adjuvant effects of exercise. Importantly, the sex difference in pain sensitivity suggests the need for separate analysis, especially when examining pain perception.Australian New Zealand Clinical Trial Registry (ACTRN:12617000374369).

Effects of non-pharmacological interventions as vaccine adjuvants in humans: a systematic review and network meta-analysis

INTRODUCTION

Psychological and behavioural may enhance vaccine effectiveness. We conducted a systematic review and network meta-analysis (NMA) to examine the effects of non-pharmacological adjuvants on vaccine effectiveness, as measured by antibody responses to vaccination.

AREAS COVERED

Electronic databases (EMBASE, Medline, PsychINFO, CINAHL) were searched from inception to 6th February 2018. This yielded 100 eligible papers, reporting 106 trials: 79 interventions associated with diet and/or nutrition; 12 physical activity interventions and 9 psychological interventions.Over half (58/106) of trials reported evidence of an enhanced antibody response to vaccination across one or more outcomes. The NMA considered the comparative effects between all intervention types, control and placebo for antibody titres (48 studies), seroconversion (25 studies) and seroprotection (23 studies) separately. The NMA provided weak evidence in support of nutritional formulae and probiotics in increasing antibody titres.

EXPERT OPINION

This review offers a comprehensive summary of the literature on non-pharmacological interventions as vaccine adjuvants. The evidence is characterised by considerable heterogeneity but provides early evidence in support of nutritional formulae and probiotic interventions. Psychological and exercise-based interventions were characterised by limited and unreliable evidence. Large, well-designed studies including consistent core outcomes and measures of intervention adherence and fidelity are required.

Timing of Vaccination after Training: Immune Response and Side Effects in Athletes

OBJECTIVES

Influenza vaccination was used to assess whether induction of immunity or side effects are influenced by the timing of the last training session before vaccination.

METHODS

Forty-five healthy athletes (36 male, 23 ± 8 yr, ≥5 training sessions per week, predominantly national competition level) were vaccinated with the tetravalent influenza vaccine; blood samples were collected immediately before and 1, 2, and 26 wk after vaccination. Athletes were randomly assigned to vaccination within 2 h after the last training session versus after 24-26 h. Influenza-specific T cells were quantified after stimulation with the vaccine based on intracellular cytokine staining. Antibodies (IgA, IgG, IgM) were quantified by enzyme-linked immunosorbent assay and neutralization assay. Participants documented resulting side effects and training restrictions using a standardized diary.

RESULTS

Both groups showed an increase in influenza-reactive CD4 T-cell levels, which peaked 1 wk after vaccination (fold changes to baseline; median (interquartile range), 3.7 (3.0-5.4; P < 0.001) in the 2-h group; 4.6 (2.8-7.4; P < 0.001) in the 26-h group) with no difference between groups (P = 0.52). Influenza-specific antibodies showed a significant increase after vaccination in both groups (at least 1.4-fold, each P < 0.001, no group differences; P = 0.24-0.97 for different antibody types). Only antibodies toward the Brisbane strain showed a trend toward significant differences in neutralization titers between groups (4-fold (2-17.8) in the 2-h group, 16-fold (4-32.9) in the 26-h group; P = 0.06), whereas other specificities did not differ (P = 0.16-0.72). No intergroup differences were found for side effects; no athlete reported a loss of training time due to the vaccination or its side effects.

CONCLUSION

Infection prophylaxis in elite athletes by influenza vaccination seems to be effective and safe. Timing of vaccination after prior training does not seem to require specific constraints.

Reflections on Bruce S. McEwen's contributions to stress neurobiology and so much more

The authors highlight, from a firsthand perspective, Bruce S. McEwen's seminal influence on the field of stress neurobiology and beyond, and how these investigations have yielded important insights, principles and critical questions that continue to guide stress research today. Featured are discussion of: 1) the important inverted-U relationship between stress/glucocorticoids and optimal physiological function, 2) stress adaptation and the role of adaptive stress responses, 3) mechanisms by which the short-term stress response promotes heightened immune function and immunity, and 4) the far reaching impact of the theoretical framework of allostasis and allostatic load-concepts that have created new bridges between stress physiology, biomedical sciences, health psychology and sociology.

Benefits of Exercise on Influenza or Pneumonia in Older Adults: A Systematic Review

A coronavirus pandemic has recently become one of the greatest threats the world is facing. Older adults are under a high risk of infection because of weaker immune systems. Therefore, the purpose of this review is to summarize the recent scientific evidence that outlines the effects of exercise on influenza or pneumonia in older adults. An electronic literature search was conducted using the WEB OF SCIENCE, SCIENCEDIRECT and GOOGLE SCHOLAR databases using the following keywords, "Exercise," "Older adult," "Influenza," and "Pneumonia." Any randomized control trials, cross-sectional and observational studies that related to this topic were all included. Twenty studies met the eligibility criteria for this review. Thirteen randomized control trials investigated the effects of exercise on the immune responses to influenza or pneumonia vaccination: seven trials employed moderate aerobic exercise, three employed resistance exercise, and the remaining three used Asian martial arts or special home-based exercises. Five cross-sectional and two observational studies examined the associations between exercise/physical condition and influenza/pneumonia. Most of the current studies suggested that prolonged moderate aerobic exercise may help to reduce the risk of influenza-related infection and improve the immune responses to influenza or pneumonia vaccination in older adults. In addition, training in traditional Asian martial arts was also found to be beneficial. Future research should focus on the different effects of moderate and vigorous exercise on influenza-related diseases.

Elite athletes on regular training show more pronounced induction of vaccine-specific T-cells and antibodies after tetravalent influenza vaccination than controls

Compliance of elite athletes with vaccination recommendations is low mainly based on concerns about side-effects and perceived poor vaccine efficacy due to continued physical training. We therefore employed seasonal influenza vaccination to investigate the effect of regular physical training on vaccine-induced cellular and humoral immunity in elite athletes and controls. Lymphocyte subpopulations and vaccine-specific T-cells were quantified and functionally characterized from 45 athletes and 25 controls before, and 1, 2 and 26 weeks after vaccination. Moreover, influenza-specific antibodies and their neutralizing function were quantified. Both groups showed a significant increase in vaccine-reactive CD4 T-cell levels which peaked one week after vaccination (p < 0.0001). The increase was significantly more pronounced in athletes (4.1-fold) compared to controls (2.3-fold; p = 0.0007). The cytokine profile changed from multifunctional T-cells co-producing IFNγ, IL-2 and TNFα to cells with restricted cytokine expression. This change in functionality was associated with a significant increase in CTLA-4 expression (p < 0.0001), which again was more pronounced in athletes. Likewise, the increase in neutralizing antibodies was stronger in athletes (p = 0.004 for H1N1; p = 0.032 for H3N2). In conclusion, both groups mounted a strong vaccine-specific cellular and humoral immunity after standard vaccination. The more pronounced increase in specific T-cells and neutralizing antibodies indicates that high frequency and intensity of training enhance vaccine-responses in elite athletes.

The impact of psychosocial stress and stress management on immune responses in patients with cancer

The range of psychosocial stress factors/processes (eg, chronic stress, distress states, coping, social adversity) were reviewed as they relate to immune variables in cancer along with studies of psychosocial interventions on these stress processes and immune measures in cancer populations. The review includes molecular, cellular, and clinical research specifically examining the effects of stress processes and stress-management interventions on immune variables (eg, cellular immune function, inflammation), which may or may not be changing directly in response to the cancer or its treatment. Basic psychoneuroimmunologic research on stress processes (using animal or cellular/tumor models) provides leads for investigating biobehavioral processes that may underlie the associations reported to date. The development of theoretically driven and empirically supported stress-management interventions may provide important adjuncts to clinical cancer care going forward.

Factors That Influence the Immune Response to Vaccination

There is substantial variation between individuals in the immune response to vaccination. In this review, we provide an overview of the plethora of studies that have investigated factors that influence humoral and cellular vaccine responses in humans. These include intrinsic host factors (such as age, sex, genetics, and comorbidities), perinatal factors (such as gestational age, birth weight, feeding method, and maternal factors), and extrinsic factors (such as preexisting immunity, microbiota, infections, and antibiotics). Further, environmental factors (such as geographic location, season, family size, and toxins), behavioral factors (such as smoking, alcohol consumption, exercise, and sleep), and nutritional factors (such as body mass index, micronutrients, and enteropathy) also influence how individuals respond to vaccines. Moreover, vaccine factors (such as vaccine type, product, adjuvant, and dose) and administration factors (schedule, site, route, time of vaccination, and coadministered vaccines and other drugs) are also important. An understanding of all these factors and their impacts in the design of vaccine studies and decisions on vaccination schedules offers ways to improve vaccine immunogenicity and efficacy.

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.

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.

The short-term stress response - Mother nature's mechanism for enhancing protection and performance under conditions of threat, challenge, and opportunity

Our group has proposed that in contrast to chronic stress that can have harmful effects, the short-term (fight-or-flight) stress response (lasting for minutes to hours) is nature's fundamental survival mechanism that enhances protection and performance under conditions involving threat/challenge/opportunity. Short-term stress enhances innate/primary, adaptive/secondary, vaccine-induced, and anti-tumor immune responses, and post-surgical recovery. Mechanisms and mediators include stress hormones, dendritic cell, neutrophil, macrophage, and lymphocyte trafficking/function and local/systemic chemokine and cytokine production. Short-term stress may also enhance mental/cognitive and physical performance through effects on brain, musculo-skeletal, and cardiovascular function, reappraisal of threat/anxiety, and training-induced stress-optimization. Therefore, short-term stress psychology/physiology could be harnessed to enhance immuno-protection, as well as mental and physical performance. This review aims to provide a conceptual framework and targets for further investigation of mechanisms and conditions under which the protective/adaptive aspects of short-term stress/exercise can be optimized/harnessed, and for developing pharmacological/biobehavioral interventions to enhance health/healing, and mental/cognitive/physical performance.

The Vaccination Model in Psychoneuroimmunology Research: A Review

This chapter explores the reasoning behind using the vaccination model to examine the influence of psychosocial factors on immunity. It then briefly discusses the mechanics of the vaccination response and the protocols used in psychoneuroimmunology vaccine research, before giving examples from the research literature of the studies examining relationships such as the association between stress and vaccination response. It also explores the ways the vaccination model can be used to answer key questions in psychoneuroimmunology, such as the following: "Does it matter when stressful life events occur relative to when the vaccine is received?" "What are the effects of prior exposure to the antigen?" "Do other psychosocial factors influence vaccine response besides stress?" Finally, it briefly considers the mechanisms underlying psychosocial factors and vaccination response associations and the future research needed to understand these better, and indeed to use current and future knowledge to improve and enhance vaccine responses in key at-risk populations.

Impact of antigens, adjuvants and strains on sexually dimorphic antibody response to vaccines in mice

Sexually dimorphic antibody response to vaccines has long been noticed. In addition to sex hormones, other factors such as antigens, adjuvants and strains of mice, as shown by indirect evidence, could also impact the sexual dimorphism. To clarify this, we immunized both gender mice of distinct strains with inactivated FMDV or HBsAg with or without adjuvants, and detected the specific antibody response of the mice. We found that in absence of adjuvants, the recombinant HBsAg but not the inactivated FMDV induced enhanced IgG antibody response in the female BALB/c mice. The o/w emulsion could facilitate the HBsAg to induce the comparable level of IgG antibodies in the male BALB/c mice as that in the females. The o/w emulsion rather than ISA206, a w/o/w emulsion, could assist the inactivated FMDV to induce higher levels of IgM antibodies in the female BALB/c mice. Moreover, the sexually dimorphic antibody response varied among the ICR, BALB/c and the F1 (BALB/c × C57BL/6) mice. Thus the data suggest that antigens, adjuvants and strains all impact the sexually dimorphic antibody response to vaccines and may provide insights for developing gender-based vaccines.

Morning vaccination enhances antibody response over afternoon vaccination: A cluster-randomised trial

OBJECTIVES

Older adults are less able to produce a protective antibody response to vaccinations. One factor that contributes to this is immune ageing. Here we examined whether diurnal variations in immune responses might extend to the antibody response to vaccination.

DESIGN

We utilised a cluster-randomised trial design.

SETTING

24 General Practices (GPs) across the West Midlands, UK who were assigned to morning (9-11am; 15 surgeries) or afternoon (3-5pm; 9 surgeries) vaccination times for the annual UK influenza vaccination programme.

PARTICIPANTS

276 adults (aged 65+ years and without a current infection or immune disorder or taking immunosuppressant medication).

INTERVENTIONS

Participants were vaccinated in the morning or afternoon between 2011 and 2013.

MAIN OUTCOME MEASURES

The primary outcome was the change in antibody titres to the three vaccine influenza strains from pre-vaccination to one month post-vaccination. Secondary outcomes of serum cytokines and steroid hormone concentrations were analysed at baseline to identify relationships with antibody responses.

RESULTS

The increase in antibody levels due to vaccination differed between morning and afternoon administration; mean difference (95% CI) for H1N1 A-strain, 293.3 (30.97-555.66) p=.03, B-strain, 15.89 (3.42-28.36) p=.01, but not H3N2 A-strain, 47.0 (-52.43 to 146.46) p=.35; those vaccinated in the morning had a greater antibody response. Cytokines and steroid hormones were not related to antibody responses. No adverse events were reported.

CONCLUSIONS

This simple manipulation in the timing of vaccine administration to favour morning vaccination may be beneficial for the influenza antibody response in older adults, with potential implications for vaccination strategies generally.

TRIAL REGISTRATION

This trial is registered with the ISRCTN (ISRCTN70898162).

Impact of Fighting on Antibody Response to Hepatitis B Virus Vaccine in Mice

Antibody responses to vaccines can be influenced by various behavioral and psychosocial factors. Few reports exist on the impact of fighting on antibody response to vaccines. This study unexpectedly found that fighting could significantly enhance antibody production in male mice immunized with hepatitis B virus (HBV) vaccines. To confirm the finding, a mouse-fighting model was established in which it was observed that only intense fighting, not mild fighting, enhanced the antibody response to HBV surface antigen in male mice, and that the frequency of fighting and active attacks during fighting showed no obvious relationship with the antibody levels in the male mice that experienced fighting. In addition, fighting can cause significant upregulation of CD80 in CD11c(+) cells in the spleen of male mice. These data suggest that fighting could influence the humoral immune response in individuals immunized with vaccines or infected with microbes.

How sex and age affect immune responses, susceptibility to infections, and response to vaccination

Do men die young and sick, or do women live long and healthy? By trying to explain the sexual dimorphism in life expectancy, both biological and environmental aspects are presently being addressed. Besides age-related changes, both the immune and the endocrine system exhibit significant sex-specific differences. This review deals with the aging immune system and its interplay with sex steroid hormones. Together, they impact on the etiopathology of many infectious diseases, which are still the major causes of morbidity and mortality in people at old age. Among men, susceptibilities toward many infectious diseases and the corresponding mortality rates are higher. Responses to various types of vaccination are often higher among women thereby also mounting stronger humoral responses. Women appear immune-privileged. The major sex steroid hormones exhibit opposing effects on cells of both the adaptive and the innate immune system: estradiol being mainly enhancing, testosterone by and large suppressive. However, levels of sex hormones change with age. At menopause transition, dropping estradiol potentially enhances immunosenescence effects posing postmenopausal women at additional, yet specific risks. Conclusively during aging, interventions, which distinctively consider the changing level of individual hormones, shall provide potent options in maintaining optimal immune functions.

Anger is associated with increased IL-6 stress reactivity in women, but only among those low in social support

BACKGROUND

Social connections moderate the effects of high negative affect on health. Affective states (anger, fear, and anxiety) predict interleukin-6 (IL-6) reactivity to acute stress; in turn, this reactivity predicts risk of cardiovascular disease progression.

PURPOSE

Here, we examined whether perceived social support mitigates the relationship between negative affect and IL-6 stress reactivity.

METHOD

Forty-eight postmenopausal women completed a standardized mental lab stressor with four blood draws at baseline and 30, 50, and 90 min after the onset of the stressor and anger, anxiety, and fear were assessed 10 min after task completion. Participants self-rated levels of social support within a week prior to the stressor.

RESULTS

Only anger was related to IL-6 stress reactivity-those experiencing high anger after the stressor had significant increases in IL-6. IL-6 reactivity was marginally associated with perceived support, but more strikingly, perceived support mitigated anger associations with IL-6 stress reactivity.

CONCLUSION

Supportive ties can dampen the relationship of anger to pro-inflammatory reactivity to acute stress. Implications to cardiovascular disease are discussed.

Nutritional and Physical Activity Interventions to Improve Immunity

Physical activity and nutrition are important in a healthy lifestyle with potential benefits to immunity often overlooked. Infection of the upper respiratory tract, and the associated symptoms, are the most frequent presentations to general practitioners and may have significant economic and social impact. In this review, we consider the role of physical activity and nutrition in improving immunity. Evidence suggests that regular moderate activity is particularly beneficial for immune enhancement and reducing the risk of infection. We also discuss some nutritional strategies. Unfortunately, the evidence for many is weak. Avoiding nutritional deficiencies seems the most pragmatic recommendation. This can be achieved with a balanced diet. Including a variety of fruits and vegetables may help ensure adequate intake of essential nutrients with little risk of excess intake of any single nutrient. Supplementation with individual nutrients is generally not recommended. Multinutrients may be beneficial for those with a preexisting deficiency but not if normal dietary intake is sufficient. Further benefit may be gained from some supplements including probiotics, bovine colostrum, and some plant-derived products (Echinacea, black elderberry, and some polyphenols) but only in specific situations/contexts. Individuals should consider their personal needs, use caution, and avoid the indiscriminate use of supplements.

Depressive symptoms and immune response to meningococcal conjugate vaccine in early adolescence

Research findings in psychoneuroimmunology document reliable, bidirectional linkages among psychological processes, the nervous system, and the immune system. However, available data are based almost entirely on animal and adult human studies; the application to children and adolescents is uncertain. We capitalized on the experimental leverage provided by a routine vaccination to examine the link between mood symptoms and the immune response to a vaccine challenge in early adolescence. One hundred twenty-six 11-year-olds for whom vaccine response data were available were assessed at prevaccination and 4 weeks, 3 months, and 6 months following vaccination; self-report ratings of depression and anxiety as well as measures of psychosocial and somatic risk were assessed prior to vaccine response. Analyses indicated that children's internalizing mood symptoms were associated with elevated and persistently higher antibody responses, with evidence extending to two of the four serogroups. The associations remained after controlling for multiple possible confounders (social class, body mass index, sleep, psychosocial risk, and pubertal status). The observed enhanced vaccine response associated with depressive and anxious symptoms in early adolescence may reflect an important developmental difference in immune system-brain interplay between adults and children, and it underscores the need for further developmental studies of psychoneuroimmunology.

Humoral responses to independent vaccinations are correlated in healthy boosted adults

BACKGROUND

Roughly half of U.S. adults do not receive recommended booster vaccinations, but protective antibody levels are rarely measured in adults. Demographic factors, vaccination history, and responses to other vaccinations could help identify at-risk individuals. We sought to characterize rates of seroconversion and determine associations of humoral responses to multiple vaccinations in healthy adults.

METHODS

Humoral responses toward measles, mumps, tetanus toxoid, pertussis, hepatitis B surface antigen, and anthrax protective antigen were measured by ELISA in post-immunization samples from 1465 healthy U.S. military members. We examined the effects of demographic and clinical factors on immunization responses, as well as assessed correlations between vaccination responses.

RESULTS

Subsets of boosted adults did not have seroprotective levels of antibodies toward measles (10.4%), mumps (9.4%), pertussis (4.7%), hepatitis B (8.6%) or protective antigen (14.4%) detected. Half-lives of antibody responses were generally long (>30 years). Measles and mumps antibody levels were correlated (r=0.31, p<0.001), but not associated with select demographic features or vaccination history. Measles and mumps antibody levels also correlated with tetanus antibody response (r=0.11, p<0.001).

CONCLUSIONS

Vaccination responses are predominantly robust and vaccine specific. However, a small but significant portion of the vaccinated adult population may not have quantitative seroprotective antibody to common vaccine-preventable infections.

Vaccine-induced inflammation attenuates the vascular responses to mental stress

Inflammation is associated with poorer vascular function, with evidence to suggest that inflammation can also impair the vascular responses to mental stress. This study examined the effects of vaccine-induced inflammation on vascular responses to mental stress in healthy participants. Eighteen male participants completed two stress sessions: an inflammation condition having received a typhoid vaccination and a control (non-inflamed) condition. Tumor necrosis factor-alpha and interleukin-6 (p's<.001) increased following vaccination, confirming modest increases in inflammation. Mental stress increased blood flow, blood pressure, heart rate, and cardiac output in both conditions (all p's<.001), but the blood flow response to stress was attenuated having received the vaccination compared to the control condition (p's<.05). These results further implicate the interaction between inflammation and the vasculature as a mechanism through which stress may trigger myocardial infarction.

Special issue on exercise immunology: current perspectives on aging, health and extreme performance

The aim of this special issue is to highlight outstanding exemplars of empirical research and review papers that reflect the breadth of current developments in exercise immunology. The contributions to this issue are categorized according to four major themes: (1) exercise and immune-aging; (2) the effects of acute exercise on cellular shifts and gene expression; (3) the effects of exercise on immune regulation during stress and disease; and (4) extreme performance and the impact of dietary counter measures on immunity. We discuss the papers appearing in this issue, in accordance with these major themes, and summarize their important contributions to this exciting and expanding field.

The effects of exercise on vaccination responses: a review of chronic and acute exercise interventions in humans

Vaccination programs, although feted for success in reducing infectious disease morbidity and mortality, are limited by vaccine efficacy, which is particularly problematic in populations with reduced immune function. Exercise has been identified as a behavioural factor that can improve immune function in some settings and cohorts, and therefore, in the setting of vaccination, it may serve as an adjuvant for immune responses. Here, we summarise the body of evidence that has investigated the effects of chronic or acute exercise interventions on vaccination responses. A systematic search of the literature was conducted including six major databases. Randomised control trials (RCTs), cross-sectional and observational studies that involved a variety of population samples and that employed any modality or intensity of acute exercise or chronic training prior to vaccine administration and measured any immune response were included. Twenty trials met the inclusion criteria for this review. Nine studies investigated the effect of acute exercise on the immune response to vaccination, whilst the remaining eleven studies investigated the effect of chronic exercise. Most of the current published literature suggests that exposure to either acute or chronic exercise significantly augments the immune response to vaccination. The clinical importance of this adjuvant action of exercise, if any, as well as variability in responsiveness across different cohorts, dose-response relationships and the optimal exercise modality to employ for this indication deserve further study.

Rudimentary signs of immunosenescence in Cytomegalovirus-seropositive healthy young adults

Ageing is associated with a decline in immune competence termed immunosenescence. In the elderly, this process results in an accumulation of differentiated 'effector' phenotype memory T cells, predominantly driven by Cytomegalovirus (CMV) infection. Here, we asked whether CMV also drives immunity towards a senescent profile in healthy young adults. One hundred and fifty-eight individuals (mean ± SD; age 21 ± 3 years, body mass index 22.7 ± 2.7 kg m(2)) were assessed for CMV serostatus, the numbers/proportions of CD4(+) and CD8(+) late differentiated/effector memory cells (i.e. CD27(-)CD28(-)/CD45RA(+)), plasma interleukin-6 (IL-6) and antibody responses to an in vivo antigen challenge (half-dose influenza vaccine). Thirty percent (48/158) of participants were CMV(+). A higher lymphocyte and CD8(+) count (both p < 0.01) and a lower CD4/CD8 ratio (p < 0.03) were observed in CMV(+) people. Eight percent (4/58) of CMV(+) individuals exhibited a CD4/CD8 ratio <1.0, whereas no CMV(-) donor showed an inverted ratio (p < 0.001). The numbers of CD4(+) and CD8(+)CD27(-)CD28(-)/CD45RA(+) cells were ~ fourfold higher in CMV(+) people (p < 0.001). Plasma IL-6 was higher in CMV(+) donors (p < 0.05) and showed a positive association with the numbers of CD8(+)CD28(-) cells (p < 0.03). Finally, there was a significant negative correlation between vaccine-induced antibody responses to the A/Brisbane influenza strain and CMV-specific immunoglobulin G titres (p < 0.05). This reduced vaccination response was associated with greater numbers of total CD8(+) and CD4(+) and CD8(+)CD27(-)CD28(-)/CD45RA(+) cells (p < 0.05). This study observed marked changes in the immune profile of young adults infected with CMV, suggesting that this virus may underlie rudimentary aspects of immunosenescence even in a chronologically young population.

A life-style physical activity intervention and the antibody response to pneumococcal vaccination in women

OBJECTIVE

To assess whether a life-style physical activity intervention improved antibody response to a pneumococcal vaccination in sedentary middle-aged women.

METHODS

Eighty-nine sedentary women completed a 16-week exercise (physical activity consultation, pedometer, telephone/e-mail prompts; n = 44) or control (advisory leaflet; n = 45) intervention. Pneumococcal vaccination was administered at 12 weeks, and antibody titers (11 of the 23 contained in the pneumococcal vaccine) were determined before vaccination and 4 weeks and 6 months later. Physical activity, aerobic fitness, body composition, and psychological factors were measured before and after the intervention.

RESULTS

The intervention group displayed a greater increase in walking behavior (from mean [standard deviation] = 82.16 [90.90] to 251.87 [202.13]) compared with the control condition (111.67 [94.64] to 165.16 [117.22]; time by group interaction: F(1,68) = 11.25, p = .001, η(2) = 0.14). Quality of life also improved in the intervention group (from 19.37 [3.22] to 16.70 [4.29]) compared with the control condition (19.97 [4.22] to 19.48 [5.37]; time by group interaction: F(1,66) = 4.44, p = .039, η(2) = 0.06). However, no significant effects of the intervention on antibody response were found (time by group η(2) for each of the 11 pneumococcal strains ranged from 0.001 to 0.018; p values all >.264).

CONCLUSIONS

Participation in a life-style physical activity intervention increased subjective and objective physical activity levels and quality of life but did not affect antibody response to pneumococcal vaccination.

Psychological stress and immunoprotection versus immunopathology in the skin

Stress is thought to suppress immune function and increase susceptibility to infections and cancer. Paradoxically, stress is also known to exacerbate autoimmune/proinflammatory disorders (eg, psoriasis, atopic dermatitis) that should be ameliorated by immunosuppression. Here we review studies showing that although chronic stress (lasting for weeks/months/years) can suppress/dysregulate immune function, acute stress (lasting for minutes to hours) can have immunoenhancing effects. Short-term stress experienced at the time of immune activation enhances dendritic cell, neutrophil, macrophage, and lymphocyte trafficking, maturation, and function, and has been shown to augment innate and adaptive immunity; therefore, depending on the conditions of immune activation, and the nature of the activating antigen, short-term stress can enhance the acquisition and expression of immunoprotection or immunopathology. In contrast, chronic stress suppresses or dysregulates innate and adaptive immune responses by altering the Type 1-Type 2 cytokine balance, inducing low-grade chronic increases in proinflammatory factors, and suppressing numbers, trafficking, and function of immunoprotective cells. Chronic stress also increases susceptibility to skin cancer by suppressing Type 1 cytokines and protective T cells while increasing regulatory/suppressor T cell number/function. It is important to recognize that the adaptive function of a physiological stress response is to promote survival. Stress-related neurotransmitters, hormones, and factors act as biological alarm signals that prepare the immune and other physiological systems for potential challenges (eg, wounding or infection) perceived by the brain (eg, detection of an attacker); however, this may exacerbate immunopathology (eg, psoriasis, atopic dermatitis) if the enhanced immune response is directed against innocuous or self-antigens, or if the system is chronically activated as seen during long-term stress. In view of the ubiquitous nature of stress and its significant effects on immunoprotection and immunopathology, it is important to further elucidate the mechanisms mediating both the salubrious and the harmful effects of stress, and to meaningfully translate findings from bench to bedside.

Effects of exercise on vaccine-induced immune responses

The role of exercise in health is well known; here we discuss the specific role of exercise in vaccination responses. Chronic exercise or high levels of physical activity have been shown to be related to improved vaccination responses in older adults, illustrating improved immune function, and conferring potentially significant public health benefit. Acute exercise has recently been examined as a potential adjuvant to vaccination; its promise for clinical use warrants further investigation, given current data.

Effects of massage on antibody responses after hepatitis B vaccination

OBJECTIVE

The aim of this study was to examine whether participation in a 4-week massage intervention is associated with reduced distress and enhanced antibody responses after hepatitis B vaccine in students embarking on academic examinations.

METHODS

Seventy medical student volunteers (36 women, 34 men) were randomly assigned to intervention or control groups. Baseline assessments were made of distress, health behaviors, and prevaccination antibodies to hepatitis B surface antigen. Intervention participants received weekly 45-minute massages before an examination period. At the end of the intervention and 1 week before commencing the examination period, all participants received an intramuscular hepatitis B vaccination and repeated the assessments completed at baseline. Serum antibody responses to hepatitis B surface antigen were measured at 2 and 6 weeks postvaccination.

RESULTS

Examinations were associated with increased distress in both the massage and the control groups: perceived stress (F(1,67) = 10.64, p = .002), anxiety (F(1,67) = 15.72, p < .001) and negative affect (F(1,66) = 5.80, p = .019); these increases did not differ between the massage and the control groups. Furthermore, massage was associated with lower levels of antibody to hepatitis B surface antigen after vaccination at both time points (F(1,63) = 6.29, p = .015).

CONCLUSIONS

These findings indicate that a brief massage intervention did not attenuate emotional distress during an examination period but did result in lowered antibody responses to vaccination. Further research is required to establish whether these effects were attributable to the nature of intervention (i.e., duration and type of massage) and/or its limited relevance to a healthy population confronting a relatively acute stressor such as examinations.

Acute exercise enhancement of pneumococcal vaccination response: a randomised controlled trial of weaker and stronger immune response

Acute exercise at the time of vaccination can enhance subsequent immune responses. However, the potential benefit of this effect will be its efficacy in boosting poor responses, and thus protection in at-risk populations. The current study tested the effect of exercise on the response to either a full- or half-dose Pneumococcal (Pn) vaccination to elicit stronger and weaker responses. Subjects were 133 young healthy adults, randomised to one of four groups: exercise or control task, receiving a full- or half-dose Pn vaccination. Prior to vaccination, exercise groups completed a 15 min arm and shoulder exercise task, control groups rested quietly. Antibody levels to 11 Pn strains were evaluated at baseline and 1-month. Across all participants, exercise groups showed significantly greater increase in antibody levels than control groups. When doses were compared, it emerged that those who exercised had significantly larger responses than those who rested in the half-dose group, but in the full-dose groups responses were similar. This data indicates the effectiveness of exercise as a vaccine adjuvant, particularly in weaker responses. Thus, given the potential public health benefits of no-cost behavioural intervention to enhance response to vaccination, testing in at-risk populations should be pursued.

Vaccination response following aerobic exercise: can a brisk walk enhance antibody response to pneumococcal and influenza vaccinations?

High intensity acute exercise at the time of vaccination has been shown to enhance the subsequent antibody response. This study examines whether an acute moderate intensity aerobic intervention prior to vaccination can enhance antibody response to pneumonia and half dose influenza vaccination. Sixty young (age (SD)=22.0 (6.1) years) and 60 older (age (SD)=57.5 (6.5) years) adults attended the laboratory on two separate occasions. At the first session, baseline antibody titres were determined, before participants completed either a brisk walk around campus at >55% of their age-predicted heart rate maximum, or a resting control condition, for 45 min. After the intervention, all participants received a full-dose pneumococcal vaccination and a half-dose influenza vaccination. Four weeks later, participants returned for a follow up blood sample. Multivariate ANOVA revealed an increase in total antibody titres against the influenza vaccine (F((12,106))=25.76, p<.001, η(2)=.75) and both the IgM (F((12,106))=17.10, p<.001, η(2)=.66) and IgG (F((12,106))=25.76, p<.001, η(2)=.75) antibody titres against the pneumococcal vaccine. However, there were no significant Time×Group interactions (p's all >.15), indicating that a 45 min brisk walk prior to vaccination did not affect antibody response to either the influenza or pneumonia vaccine. The results suggest that higher intensity exercise is necessary to augment antibody response to vaccination.

Coping in an intermittent swim stress paradigm compromises natural killer cell activity in rats

The effects of intermittent swim stress and stressor controllability on natural killer cell activity (NKCA) was examined. Significant decreases in splenic NKCA were observed immediately post-stress, but only when the stress was controllable. Although decreased NKCA was also observed in yoked rats subjected to the same stressor, it failed to attain statistical significance. Previous results suggest these effects are not due to corticosterone. The results suggest a cost of coping on the acute, in vitro immune measure of NKCA.

Using vaccinations to assess in vivo immune function in psychoneuroimmunology

Finding clinically relevant measures of immune function is an important challenge in psychoneuroimmunological research. Here, we discuss the advantages of the vaccination model, and provide guidance on the methodological decisions that are important to consider in the use of this technique. These include the choice of vaccination, timing of assessments, and the available outcome measures.

Acute Exercise as an Adjuvant to Influenza Vaccination

Acute exercise prior to vaccine administration can improve the immune response. Animal data are now supported by human trials, which have shown that immune responses are enhanced by a bout of acute exercise before innoculation; this effect is particularly prominent in vaccines that normally produce weak immune responses. Although there remain many aspects of this phenomenon to be investigated, including task characteristics such as duration and form of exercise, it appears that even a moderate bout of exercise of the muscles into which vaccine will be administered can enhance the antibody response. In this review, the authors will summarize the animal and human literature and discuss the investigation of potential mechanisms of acute exercise–induced immunoenhancement.

Altered human neutrophil function in response to acute psychological stress

OBJECTIVE

To examine the effects of an acute laboratory psychological stress task on neutrophil function, specifically phagocytosis of Escherichia coli and stimulated superoxide production in human neutrophils. There is mounting evidence that acute stress is associated with short-term increases in a number of immune indices.

METHODS

Participants were 40 (n = 20 females) university students (mean age, 25.9 ± 4.56 years). Blood samples to determine neutrophil function by flow cytometry were taken at the end of resting baseline, during an acute stress task, and during recovery. The stress task was a 10-minute time-pressured mental arithmetic challenge with social evaluation.

RESULTS

There was an acute increase in phagocytic ability, p = .047, η(2)p = 0.076, and a reduction of superoxide production, p = .026, η(2)p = 0.101, associated with the stress task relative to baseline.

CONCLUSION

These findings suggest that neutrophil bactericidal function may be sensitive to mental challenge tasks that provoke acute psychological stress. Further research is needed to replicate the observed psychological stress-induced changes in neutrophil function.

Understanding stress-induced immunosuppression: exploration of cytokine and chemokine gene profiles in chicken peripheral leukocytes

At present, the poultry meat and egg industry has gained a lot of ground, being viewed as a provider of a healthy alternative to red meat and other protein sources. If this trend is to be maintained, solutions must be found to improve resistance of chickens to disease, which often is weakened by stressful conditions. In poultry, stress-induced immunosuppression is manifested by failures in vaccination and increased morbidity and mortality of flocks. Currently, several modern cellular and molecular approaches are being used to explore the status of the immune system during stress and disease. It is likely that these new techniques will lead to the development of new strategies for preventing and controlling immunosuppression in poultry. Using quantitative reverse transcription-PCR assays, a broad spectrum of cytokine, chemokine, and their receptor genes can be quantified in birds and then be used as markers to assess the effects of stress on the immune system. Currently, we are investigating immune and endocrine interactions in the chicken, in particular the cells and molecules that are known to be involved in such interactions in mammals. We have evaluated the effects of corticosterone administration in drinking water on peripheral lymphocyte and heterophil cytokine and chemokine gene profiles. In particular, there seems to be effects on cytokine and chemokine mRNA expression levels in both lymphocytes and heterophils, especially expression of the proinflammatory cytokines interleukin (IL)-1beta, IL-6, and IL-18 and chemokines C-C motif, ligand 1 inflammatory (CCLi1); C-C motif, ligand 2 inflammatory (CCLi2); C-C motif, ligand 5 (CCL5); C-C motif, ligand 16 (CCL16); C-X-C motif ligand 1 inflammatory (CXCLi1); and C-X-C motif ligand 2 inflammatory (CXCLi2), which are initially upregulated and are potentially involved in modulating the adaptive immune response. A chronic treatment with corticosterone downregulates proinflammatory cytokines and chemokines, suggesting that the delayed effects of chronic stress can suppress the immune response. Messenger RNA expression levels of transforming growth factor-beta4 (TGF-beta4) are also upregulated in cortisosterone-treated birds. It appears that the balance between T-helper (Th) 1 and Th2/T regulatory cytokine production is altered in conditions associated with significant changes in plasma corticosterone concentration. Experiments are underway to decipher the cytokine and chemokine responses to vaccination and bacterial challenge on the background of stress-induced immunosuppression.

Exercise intensity does not influence the efficacy of eccentric exercise as a behavioural adjuvant to vaccination

Acute exercise prior to vaccination can improve the antibody response to influenza vaccination. However, both the optimal exercise protocol and the mechanisms underpinning this adjuvant effect remain unclear. The aim of the current study was to determine whether exercise intensity influenced the efficacy of the intervention. One hundred and sixty healthy young adults were randomly assigned to a resting control group or one of three intervention groups, who exercised at an intensity of 60%, 85%, or 110% of their pre-determined concentric one repetition maxima. The exercise groups performed 50 repetitions of the eccentric portion of both bicep curl and lateral raise movements. All participants then immediately received a reduced dose (50% recommended dose) influenza vaccine. Antibody titres to the three viral strains contained in the vaccine were measured at baseline and at 28 days post-vaccination. Compared to the control group, exercise enhanced the antibody response to the least immunogenic of the three strains (B/Florida). In addition, the exercise groups showed an augmented response to the A/Uruguay strain compared to control; however, this effect was observed only in men. The intervention had no effect on the antibody responses to the most immunogenic strain, A/Brisbane. Finally, antibody responses were unrelated to the intensity of the exercise bout. In conclusion, our findings provide further evidence of exercise as an adjuvant to enhance vaccination responses. The results further show that responses to the low-immunogenic antigens are particularly responsive to augmentation by acute eccentric exercise.

The effects of vaccine timing on the efficacy of an acute eccentric exercise intervention on the immune response to an influenza vaccine in young adults

An acute bout of exercise prior to vaccination can improve the antibody and cell-mediated responses to influenza vaccination. The mechanisms underpinning this adjuvant effect remain unclear, and further investigation to determine the optimal exercise protocol is warranted. The aim of the current study was to determine whether exercise augmented the immune response to vaccination, and whether the timing of exercise relative to vaccination affected the efficacy of the intervention. One hundred and fifty-six (76 men) healthy participants were randomly assigned to a control group or one of three intervention groups who exercised immediately, 6h or 48 h prior to administration of a standard trivalent influenza vaccine. The exercise groups performed 50 repetitions of the eccentric portion of both the bicep curl and lateral raise movements at an intensity eliciting 85% of each participant's pre-determined concentric one repetition maxima. Antigen-specific serum antibody titres were measured at baseline and 28 days post-vaccination as indicators of the humoral response. All three viral strains elicited strong antibody responses; however, eccentric exercise did not further augment any antibody responses compared to the control group. Cell-mediated immunity at 28 days post-vaccination was determined by measuring the IFN-gamma response to in vitro stimulation of the blood with whole vaccine. There were no differences in cell-mediated immunity among the groups. Although these null findings were unexpected, they are consistent with previous research showing that exercise-induced immunoenhancement was only observed when the control group had relatively poor responses. In conclusion, it is likely that the robust immune responses to the vaccine observed in this study may have limited any further immune enhancement by exercise.

Antibody response to vaccination as a marker of in vivo immune function in psychophysiological research

The hunt for novel tools to investigate empirical questions is ever present in psychophysiological research. Antibody response to vaccination has received increasing attention over recent years as a useful measure of in vivo immune function. There is now considerable evidence that the magnitude of the antibody response to vaccination is associated with a wide range of psychosocial factors. Further, there are preliminary indications that manipulating psychosocial variables, using both chronic and acute interventions, can also alter the efficacy of the vaccination. This review will discuss the theoretical and clinical relevance of the vaccine model in this context, and will address key methodological considerations for researchers considering adopting this approach. The review will also address how the strategic use of this model could help researchers further elucidate some of the remaining theoretical issues.

Dispositional optimism and stress-induced changes in immunity and negative mood

Evidence suggests that optimism may be protective for health during times of heightened stress, yet the mechanisms involved remain unclear. In a double-blind placebo-controlled study, we recently showed that acute psychological stress and an immune stimulus (Typhim-Vi typhoid vaccine) synergistically increased serum levels of interleukin-6 (IL-6) and negative mood in 59 healthy men. Here we carried out further analysis of this sample to investigate the relationship between dispositional optimism and stress-induced changes in immunity and mood. Volunteers were randomly assigned to one of four experimental conditions in which they received either typhoid vaccine or saline placebo, and then rested or completed two mental tasks. In the stress condition, optimism was inversely related to IL-6 responses, independent of age, BMI, trait CES-D depression and baseline IL-6. This relationship was present across both stress groups (combining vaccine and placebo) and was not present in the vaccine/stress group alone, suggesting that optimism protects against the inflammatory effects of stress rather than vaccine per se. Typhoid vaccine induced a significant increase in participants' circulating anti-Vi antibody levels. Stress had no effect on antibody responses overall. However, in the vaccine/stress group, there was a strong positive association between optimism and antibody responses, indicating that stress accentuated the antibody response to vaccine in optimists. Across the complete sample, more optimistic individuals had smaller increases in negative mood and less reduction in mental vigour. Together these findings suggest that optimism may promote health, by counteracting stress-induced increases in inflammation and boosting the adjuvant effects of acute stress.

A hassle a day may keep the pathogens away: The fight-or-flight stress response and the augmentation of immune function

Stress is known to suppress or dysregulate immune function and increase susceptibility to disease. Paradoxically, the short-term fight-or-flight stress response is one of nature's fundamental defense mechanisms that galvanizes the neuroendocrine, cardiovascular, and musculoskeletal systems into action to enable survival. Therefore, it is unlikely that short-term stress would suppress immune function at a time when it may be critically required for survival (e.g., in response to wounding and infection by a predator or aggressor). In fact, studies have shown that stress can enhance immune function under certain conditions. Several factors influence the direction (enhancing versus suppressive) of the effects of stress on immune function: (1) DURATION: acute or short-term stress experienced at the time of activation of an immune response enhances innate and adaptive immune responses. Chronic or long-term stress can suppress or dysregulate immune function. (2) Leukocyte distribution: compartments (e.g., skin), that are enriched with immune cells during acute stress show immuno-enhancement, while those that are depleted of leukocytes (e.g., blood), show immuno-suppression. (3) The differential effects of physiologic versus pharmacologic stress hormones: Endogenous hormones in physiological concentrations can have immuno-enhancing effects. Endogenous hormones at pharmacologic concentrations, and synthetic hormones, are immuno-suppressive. (4) Timing: immuno-enhancement is observed when acute stress is experienced during the early stages of an immune response while immuno-suppression may be observed at late stages. The type of immune response (protective, regulatory/inhibitory, or pathological) that is affected determines whether the effects of stress are ultimately beneficial or harmful for the organism. Arguments based on conservation of energy have been invoked to explain potential adaptive benefits of stress-induced immuno-suppression, but generally do not hold true because most mechanisms for immuno-suppression expend, rather than conserve, energy. We propose that it is important to study, and if possible, to clinically harness, the immuno-enhancing effects of the acute stress response that evolution has finely sculpted as a survival mechanism, just as we study its maladaptive ramifications (chronic stress) that evolution has yet to resolve.