Basketball exercise and secretory immunoglobulin A

Acute and chronic effects of physical exercise on IgA and IgG levels and susceptibility to upper respiratory tract infections: a systematic review and meta-analysis

This systematic review and meta-analysis aimed at evaluating acute and chronic effects of physical exercise on IgA and IgG levels, as well as its relationship with the susceptibility to develop upper respiratory tract infections (URTI). This systematic review and meta-analysis was conducted and reported in accordance with PRISMA statement. A systematic search of PubMed, Web of Science, and EMBASE was performed in July 2020. This systematic review and meta-analysis included studies in which participants performed acute exercise or chronic physical training and were subjected to analyses of URTI incidence and concentrations of IgA and IgG. The selected studies for systematic review were divided into the following three groups: (I) trials that evaluated the effects of acute exercise in sedentary subjects, (II) trials that evaluated the effects of acute exercise in athletes/trained individuals, and (III) trials that evaluated the effects of chronic physical training on the incidence of URTI, as well as on the levels of IgA and IgG. Acute exercise increases the IgA levels in trained subjects but does not affect its levels in untrained subjects. Such increase in IgA levels induced by acute exercise is greater in trained individual that performed ultramarathon. On the other hand, chronic physical training reduces IgA levels in both trained and untrained subjects, does not change IgA levels in non-military subjects, besides from not affecting IgG levels. The present systematic review and meta-analysis indicates that acute exercise positively influences IgA levels in trained individuals, being this effect pronounced when a strenuous exercise such as ultramarathon is executed. Chronic physical training, in turn, does not affect IgG levels.

Salivary secretory immunoglobulin A variation between female varsity athletes and nonathletes

OBJECTIVES

Exercise can lead to changes in immune function. To further investigate this relationship, we examined possible differences in salivary secretory immunoglobulin A (sIgA) secretion rates among female college athletes and nonathlete students. We predicted that athletes would have higher sIgA secretion rates than nonathletes and show greater declines in sIgA during the study period as intensive exercise training continued.

METHODS

We recruited 52 female participants aged 18-22 years (13 swimmers, 20 runners, and 19 nonathletes). We collected two saliva samples from each participant: baseline and a second sample 2 weeks later. Additionally, participants reported minutes of cardiovascular activity performed per week and completed a survey that included a modified Profile of Mood States and the Undergraduate Stress Questionnaire.

RESULTS

We found no significant differences in mean salivary sIgA secretion rates between athletes and nonathletes. Salivary sIgA significantly increased between sample collections for both groups, with nonathletes exhibiting a greater increase in sIgA than athletes. Cardiovascular activity was not associated with sIgA secretion rates. Illness status was a significant positive predictor of sIgA secretion rates.

CONCLUSIONS

Cardiovascular activity did not predict salivary sIgA secretion rates in this sample of female college students, and athletes did not show significantly different sIgA secretion rates than nonathletes. Together, these findings suggest that exercise may not be associated with altered immune function in well-nourished college-aged women. The increase in secretion rates among both athletes and nonathletes suggests that additional factors shared by both groups may have led to increases.

Salivary Biomarkers and Training Load During Training and Competition in Paralympic Swimmers

Context: Stress responses in athletes can be attributed to training and competition, where increased physiological and psychological stress may negatively affect performance and recovery. Purpose: To examine the relationship between training load (TL) and salivary biomarkers immunoglobulin A (IgA), alpha-amylase (AA), and cortisol across a 16-wk preparation phase and 10-d competition phase in Paralympic swimmers. Methods: Four Paralympic swimmers provided biweekly saliva samples during 3 training phases—(1) normal training, (2) intensified training, and (3) taper—as well as daily saliva samples in the 10-d Paralympic competition (2016 Paralympic Games). TL was measured using session rating of perceived exertion. Results: Multilevel analysis identified a significant increase in salivary immunoglobulin A (sIgA: 94.98 [27.69] μg·mL−1), salivary alpha-amylase (sAA: 45.78 [19.07] μg·mL−1), and salivary cortisol (7.92 [2.17] nM) during intensified training concurrent with a 38.3% increase in TL. During the taper phase, a 49.5% decrease in TL from the intensified training phase resulted in a decrease in sIgA, sAA, and salivary cortisol; however, all 3 remained higher than baseline levels. A further significant increase was observed during competition in sIgA (168.69 [24.19] μg·mL−1), sAA (35.86 [16.67] μg·mL−1), and salivary cortisol (10.49 [1.89] nM) despite a continued decrease (77.8%) in TL from the taper phase. Conclusions: Results demonstrate that performance in major competition such as Paralympic games, despite a noticeable reduction in TL, induces a stress response in athletes. Because of the elevated stress response observed, modifications to individual postrace recovery protocols may be required to enable athletes to maximize performance across all 10 d of competition.

Realising the Potential of Urine and Saliva as Diagnostic Tools in Sport and Exercise Medicine

Accurate monitoring of homeostatic perturbations following various psychophysiological stressors is essential in sports and exercise medicine. Various biomarkers are routinely used as monitoring tools in both clinical and elite sport settings. Blood collection and muscle biopsies, both invasive in nature, are considered the gold standard for the analysis of these biomarkers in exercise science. Exploring non-invasive methods of collecting and analysing biomarkers that are capable of providing accurate information regarding exercise-induced physiological and psychological stress is of obvious practical importance. This review describes the potential benefits, and the limitations, of using saliva and urine to ascertain biomarkers capable of identifying important stressors that are routinely encountered before, during, or after intense or unaccustomed exercise, competition, over-training, and inappropriate recovery. In particular, we focus on urinary and saliva biomarkers that have previously been used to monitor muscle damage, inflammation, cardiovascular stress, oxidative stress, hydration status, and brain distress. Evidence is provided from a range of empirical studies suggesting that urine and saliva are both capable of identifying various stressors. Although additional research regarding the efficacy of using urine and/or saliva to indicate the severity of exercise-induced psychophysiological stress is required, it is likely that these non-invasive biomarkers will represent "the future" in sports and exercise medicine.

Influence of carbohydrate ingestion on salivary immunoglobulin A following resistance exercise

Background

Heavy exercise stresses immune function, however carbohydrate (CHO) supplementation has been shown to attenuate the decline in some measures of immune function after exercise. The purpose of the study was to investigate the impact of CHO supplementation on salivary immunoglobulin A (s-IgA) levels, interleukin 2 (IL-2), and interleukin 5 (IL-5), following an acute bout of resistance exercise (RE).

Methods

Ten resistance trained male collegiate athletes (21±2 yr; 174±6 cm, 80±11kg, 14%±4% fat) performed RE consisting of four exercises (leg press, lat pull-downs, bench press, and leg curls). Volunteers performed four sets of 10 repetitions at 65% of 1-RM, with 2 min rest between sets for all exercises. Subjects consumed either CHO beverage (1 g•kg^-1 body weight) or placebo (P) prior to, during, and after RE (randomized, double blind design). Saliva and venous blood were collected pre-, post- and 90 min post-exercise.

Results

No change occurred in s-IgA from rest relative to osmolality or as a secretion rate (p > 0.05). IL-2 levels were unchanged by exercise in both trials (time effect p = 0.342). IL-5 was significantly (time effect p = 0.04) decreased between rest (1.55 ± 0.07 pg•ml^-1) and 90 min post-exercise (0.96 ± 0 .11 pg•ml^-1), with no difference between treatments (group x time effect p = 0.610). There was no time-by-treatment interaction (p < 0.05) observed between CHO and P treatments for s-IgA or IL-5.

Conclusion

IL-5 decreases after RE, but s-IgA and IL-2 levels remain stable. CHO ingestion prior to-, during or following RE did not appear to alter salivary immune responses.

Concentrations of salivary testosterone, cortisol, and immunoglobulin A after supra-maximal exercise in female adolescents

The aim of this study was to examine the effect of supra-maximal exercise on circulating concentrations of salivary testosterone, salivary cortisol, and salivary immunoglobulin A in female adolescents. Nineteen apparently healthy females aged 15-16 years participated in this study. All participants completed 668 s sprints, interspersed with 30 s recovery intervals on a cycle ergometer. Salivary testosterone, cortisol, and immunoglobulin A samples were taken before and 5 min after exercise. Experimental procedures continued over two mornings, at least 3 h after a light breakfast. Participants refrained from performing any strenuous physical activity for at least 24 h prior to the exercise test. None of the participants were engaged in a structured training programme. The group mean (± s) for peak power output was 562 ± 113.0 W. Female adolescents recruited for this study showed no changes in salivary testosterone, cortisol or immunoglobulin A following repeated bouts of supra-maximal cycling (P > 0.05). To date, there has been a paucity of information concerning adolescents' hormonal and mucosal immune function responses to supra-maximal exercise. Our data provide further guidance with regard to physical activities and sports prescription for female adolescents. Further research, on a larger sample of females, is required to elucidate the physiological significance of these findings.

Salivary cortisol and immunoglobulin A responses during golf competition vs. practice in elite male and female junior golfers

The purpose of this study was to investigate the stress and immune responses to a competition in elite male and female junior golfers. Six male (16.2 +/- 1.4 years) and 6 female junior golfers (16.4 +/- 1.1 years) completed salivary collections during competition vs. practice rounds on 2 different days. Salivary samples were collected on 4 occasions (rest, before, during, and after rounds). Salivary cortisol and IgA were measured for stress and immune responses, respectively. Our results were as follows: (a) Salivary cortisol level was higher in competition than practice in male golfers (p = 0.009) but it was similar in female golfers. In male golfers, salivary cortisol level was higher before a round than at rest (p = 0.029), but it was higher after rounds than at rest (p = 0.016) in female golfers. (b) Salivary IgA was elevated during competition than during practice rounds in male golfers (p = 0.019), but not in females (p = 0.152). Salivary IgA was not significantly different among salivary collection times although it tended to be elevated during and after rounds for both male and female golfers. In conclusion, salivary cortisol and IgA were elevated during golf competition compared with practice in male junior golfers, but they were not in female golfers. Furthermore, salivary cortisol was higher before a round than rest in men, but it was higher after a round than rest in women. Both male and female junior golfers, however, showed similar salivary IgA responses during golf. Our results suggest that sex might play a role on stress and immune responses during a game of golf in elite junior golfers.

Immune Response to Resistance Exercise

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

Imunoglobulina A salivar (IgA-s) e exercício: relevância do controle em atletas e implicações metodológicas

O objetivo do presente estudo é realizar uma análise e discussão dos principais achados envolvendo o comportamento da imunoglobulina A salivar (IgA-s) em relação ao estímulo do exercício e evidenciar a importância de seu controle em atletas. O exercício físico é um importante modulador das características do sistema imune, sobretudo do comportamento da IgA-s, componente fundamental na proteção de infecções do trato respiratório superior (ITRS). No entanto, a relação direta entre baixas concentrações de IgA-s e ITRS precisa de mais evidências para ser confirmada. As concentrações de IgA-s durante e logo após um exercício intenso diminuem, deixando o indivíduo mais suscetível à infecção, porém, atletas envolvidos em atividades extenuantes não são clinicamente imunodeficientes, comparados com indivíduos sedentários. Essas modificações são transitórias, com retorno aos valores normais após aproximadamente 48 horas de repouso. A razão dessas alterações não é clara, mas se apresenta multifatorial: elevação de hormônios estressores; fatores nutricionais; ação de espécies reativas de oxigênio; e estresse psicológico. Apesar do efeito transitório das alterações provocadas nos elementos do sistema imune frente ao exercício, observa-se diferença na variabilidade da IgA-s em populações com diferentes níveis de condicionamento. Diferenças metodológicas - como o protocolo de exercício, o método de coleta, armazenamento e manipulação da saliva, a forma de expressão da IgA-s, o nível de hidratação, o controle da dieta, a sazonalidade do período de competição, a aclimatação entre outros fatores - devem ser levadas em consideração para comparação entre os estudos. Além disso, ajudam a explicar, em parte, os resultados adversos envolvendo exercício moderado e os intermitentes, em que se encontram aumento, redução e até ausência de alteração nos níveis de IgA-s. Investigações de elementos inovadores, como os toll-like receptors, e o avanço tecnológico podem colaborar para aumentar as evidências sobre o tema.

Resistance exercise sessions do not provoke acute immunosuppression in older women

It has been suggested that elderly people are more susceptible to infectious diseases because of immunosenescence. The well-described transient immunosuppressive effect of exercise may increase health risks in such populations. Although resistance training has been recommended to older individuals, little is known regarding its acute effects on immune indexes. This study examined the acute effects of resistance exercise sessions performed at different intensities (50 vs. 80% of one-repetition maximum [1RM]) on salivary immunoglobulin A (IgA), total leukocytes, lymphocytes and their subsets, and the cortisol levels of older women. Fifteen physically independent elderly women (mean age = 67.5 +/- 3.9 years) underwent, in a randomized manner, two experimental sessions comprising resistance exercise for the major muscular groups or one control session without exercise. Session 1 consisted of two sets of 13 repetitions at 50% 1RM, whereas session 2 consisted of two sets of eight repetitions at 80% 1RM. Blood and saliva samples were collected at rest, immediately after, and at 3 and 48 hours after the completion of the sessions. Blood cortisol, total leukocytes, lymphocytes and their subpopulations, and salivary IgA were measured by standard techniques. Overall, resistance exercise sessions failed to provoke significant decline on the examined immune function indexes. Instead, resistance exercise sessions induced significant elevation in salivary IgA levels, but this was not observed after the control session. Also, experimental sessions did not induce significant elevations in blood cortisol. It was concluded that resistance exercise sessions performed at 50 or 80% of 1RM do not present suppressive effects on the studied immune parameters. Conversely, a transient elevation was observed in salivary IgA levels, which requires support in future investigations. Taken together, the observed results suggest that elderly women can engage in resistance training programs without negative acute effects on the studied parameters of the immune system.

Exercise enhances vaccine-induced antigen-specific T cell responses

Regular moderate exercise has been proposed to enhance immune function, but its effects on immunity and their consequences have not been well studied. Mice without (AL) or with access (AL+EX) to voluntary running wheels were vaccinated with a model antigen (ovalbumin (OVA)) via intranasal or subcutaneous routes to target the mucosal and systemic immune compartments, respectively. EX enhanced OVA-specific CD4(+) T cell cytokine production and proliferation in all lymphoid organs examined without changes in cell distribution in any organ. These results suggest that coupling moderate exercise with vaccination may enhance vaccine efficacy for the prevention and/or therapy of numerous diseases.

Mucosal IgA and URTI in American college football players: a year longitudinal study

PURPOSE

The purpose of this study was: (a) to evaluate secretory immunoglobulin A (s-IgA) over a 12-month time period in college football players, and (b) to assess which of the commonly used standard methods of reporting s-IgA, either alone or in combination, serves as the best predictor of incidence of upper respiratory tract infection (URTI).

METHODS

One hundred college-aged males (75 varsity college football athletes, 25 nonfootball controls) were studied at eight points over a 12-month period. Resting mucosal IgA, protein and osmolality levels were determined from saliva using established procedures. In addition, incidence of URTI over the 12-month study duration was calculated from completed standard research logs. Repeated-measures ANOVA were conducted on the dependent variables and eight separate stepwise multiple regression analyses were conducted to predict the dependent variable "number of colds" by the independent variables, s-IgA, saliva flow rate, secretion rate of s-IgA, protein, s-IgA:protein, osmolality and s-IgA:osmolality at each data collection point.

RESULTS

There was a significant main effect for group, time, and the group x time interaction for s-IgA, the secretion rate of s-IgA, and the number of colds. In the regression model, the only variable that made a significant contribution to the variance at all time points was the secretion rate of s-IgA.

CONCLUSION

These findings suggest that a season of training in American football results in a significant decrease in both s-IgA and the secretion rate of s-IgA as well as an increase in the incidence of URTI. Among the various methods commonly employed to express s- IgA levels, the secretion rate of s-IgA may be the most useful clinical biomarker to predict the incidence of URTI.

Effects of physical activity, body fat, and salivary cortisol on mucosal immunity in children

This study examined relationships among physical activity, body composition, and stress- and immunity-related variables in fifth grade children (10-11 yr) in Southern Ontario. The 29 boys and 32 girls, who participated in the study, performed a 20-m shuttle run for prediction of aerobic fitness. Bioelectrical impedance was used to assess relative body fat. Standardized questionnaires were used to determine physical activity-related variables and frequency of upper respiratory tract infection (URTI). Resting saliva samples were collected and tested for resting cortisol and resting secretory immunoglobulin A (SIgA). Subjects wore a pedometer for 48 h to estimate their average total distance traveled per day. SIgA was significantly correlated with reported URTIs but was not related to salivary cortisol, physical activity, fitness level, or relative body fat. Children who spent more time in sport activities and had higher aerobic fitness reported fewer "sick" days. Children with body fat higher than 25% reported significantly (P < 0.05) more sick days than the rest of the cohort. There were no gender differences in SIgA, URTI frequency, and cortisol levels. The test-retest reproducibility for salivary cortisol was 0.66 (P < 0.01), whereas long-term SIgA reproducibility was nonsignificant for repeated measurements taken after 6 wk. Resting secretory immunity was not strongly related to fitness and physical activity, but there was evidence that reduced physical activity and excess body fat can result in higher URTI incidence.

Salivary IgA response to prolonged exercise in a cold environment in trained cyclists

PURPOSE

The purpose of the present study was to determine the effect of a prolonged bout of exercise in freezing cold conditions on saliva immunoglobulin A (s-IgA) responses in endurance-trained males.

METHODS

Using a randomized cross-over design, 15 trained male cyclists cycled for 2 h on a stationary ergometer at 70% VO(2max) in an environmental chamber on one occasion at a temperature of -6.4 +/- 0.1 degrees C (cold) and on another occasion at a temperature of 19.8 +/- 0.2 degrees C (control). Trials began at 12:30 h to avoid the fall in s-IgA concentration that occurs during the morning hours. Unstimulated whole-saliva samples were collected over a 2-min period at preexercise, postexercise, and 2-h postexercise. The s-IgA concentration was determined using a sandwich-type ELISA method.

RESULTS

Saliva flow rate decreased postexercise by 31%, returning to preexercise levels by the 2-h postexercise collection (main effect of time: < 0.01). The decrease in saliva flow rate postexercise in the control trial (39% compared with 22% on cold trial) approached significance (interaction: = 0.08) and may have accounted for the corresponding increase in s-IgA concentration postexercise in the control trial (s-IgA concentration: control preexercise; 91 +/- 12; postexercise; 110 +/- 13 mg x L(-1); < 0.05). Saliva IgA secretion rate decreased postexercise by 19.5% returning to preexercise levels by 2-h postexercise measure (main effect of time: < 0.05).

CONCLUSIONS

These data show that performing a bout of prolonged exercise results in a reduction in s-IgA secretion rate. Additionally, these data demonstrate that performing prolonged exercise in freezing cold conditions does not influence saliva flow rate or s-IgA secretion rate responses to prolonged exercise.

Circadian effects on the acute responses of salivary cortisol and IgA in well trained swimmers

OBJECTIVE

To examine whether time of day significantly affects salivary cortisol and IgA levels before and after submaximal swimming.

METHODS

Fourteen male competitive swimmers (mean (SD) age 18 (3.2) years) volunteered to participate in the study. In a fully randomised, cross over design, each subject performed 5 x 400 m front crawl at 85 (1.2)% of their seasonal best time (277 (16) seconds), with one minute rest between each 400 m, at 0600 and 1800 hours on two separate days. Timed, unstimulated saliva samples were collected before and after exercise. Saliva samples were analysed for cortisol and IgA by radioimmunoassay and single radial immunodiffusion respectively.

RESULTS

Significant time of day effects (am and pm respectively) were observed in IgA concentration (0.396 (0.179) v 0.322 (0.105) mg/ml, p<0.05), IgA secretory rate (0.109 (0.081) v 0.144 (0.083) mg/min, p<0.01), and saliva flow rate (0.31 (0.23) v 0.46 (0.22) ml/min, p<0.001) before exercise (all values mean (SD)). Differences in cortisol levels before exercise (1.09 (0.56) v 0.67 (0.94) microg/dl) approached significance (p = 0.059). The exercise protocol did not significantly affect IgA concentration and secretory rate (p>0.05) but, in comparison with values before exercise, caused significant alterations in cortisol (p<0.01) and saliva flow rate (p<0.01). There was no significant interaction effect of time of day by exercise on any salivary variables measured (p>0.05). However, most of the values of the salivary variables before exercise were significantly inversely related to their exercise induced response (p<0.05).

CONCLUSION

These results suggest a significant circadian variation in the variables measured before exercise, without showing a significant effect on their acute responses to exercise.

Carbohydrate and fluid intake affect the saliva flow rate and IgA response to cycling

PURPOSE

The purpose of this study was to examine the effect of regular CHO beverage ingestion and restricted fluid intake on various salivary parameters during prolonged cycle exercise.

METHODS

In a randomized block design, 15 recreationally active men cycled for 2 h at 60% VO2max on three occasions, separated by 1 wk. On the CHO and placebo (PLA) treatments, subjects consumed either a glucose (60 g x L(-1)) or placebo drink before (400 mL), during (150 mL every 15 min), and after (400 mL) the exercise. On the restricted fluid intake (RFI) treatment subjects were given a total of 200 mL of placebo fluid to take as desired every 15-min during the exercise. Timed, unstimulated saliva samples were collected preexercise, at 1, 1.5, and 2 h of exercise and at 1 h postexercise. Blood samples were obtained from a subset of 8 subjects preexercise, postexercise, and at 1 h postexercise.

RESULTS

Postexercise plasma glucose levels were 18% and 20% lower on the PLA and RFI treatments, respectively, compared with the CHO treatment (P < 0.01). Saliva flow rates were significantly higher on the CHO treatment compared with the RFI treatment at 1.5 h and 2 h of exercise (P < 0.01 and P < 0.05, respectively). Salivary IgA (s-IgA) concentration was significantly lower on the CHO treatment compared with the RFI treatment throughout the exercise (P < 0.05). No other differences were seen between treatments for either saliva flow rate or s-IgA concentration. Neither s-IgA secretion rate, alpha-amylase activity, nor alpha-amylase secretion rate were affected by treatment.

CONCLUSIONS

These findings suggest that CHO and fluid intake influence the s-IgA and saliva flow rate response to prolonged submaximal exercise.

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

The present review examines the effects of exercise on mucosal immunity in recreational and elite athletes and the role of mucosal immunity in respiratory illness. Habitual exercise at an intense level can cause suppression of mucosal immune parameters, while moderate exercise may have positive effects. Saliva is the most commonly used secretion for measurement of secretory antibodies in the assessment of mucosal immune status. Salivary IgA and IgM concentrations decline immediately after a bout of intense exercise, but usually recover within 24 h. Training at an intense level over many years can result in a chronic suppression of salivary immunoglobulin levels. The degree of immune suppression and the recovery rates after exercise are associated with the intensity of exercise and the duration or volume of the training. Low levels of salivary IgM and IgA, particularly the IgA1 subclass, are associated with an increased risk of respiratory illness in athletes. Monitoring mucosal immune parameters during critical periods of training provides an assessment of the upper respiratory tract illness risk status of an individual athlete. The mechanisms underlying the mucosal immune suppression are unknown.

Saliva composition and exercise

Little attention has been directed toward identifying the changes which occur in salivary composition in response to exercise. To address this, our article first refers to the main aspects of salivary gland physiology. A knowledge of the neural control of salivary secretion is especially important for the understanding of the effects of exertion on salivary secretion. Both salivary output and composition depend on the activity of the autonomic nervous system and any modification of this activity can be observed indirectly by alternations in the salivary excretion. The effects of physical activity (with reference to factors such as exercise intensity and duration, or type of exercise protocol) on salivary composition are then considered. Exercise might indeed induce changes in several salivary components such as immunoglobulins, hormones, lactate, proteins and electrolytes. Saliva composition might therefore be used as an alternative noninvasive indicator of the response of the different body tissues and systems to physical exertion. In this respect, the response of salivary amylase and salivary electrolytes to incremental levels of exercise is of particular interest. Beyond a certain intensity of exercise, and coinciding with the accumulation of blood lactate (anaerobic threshold or AT), a 'saliva threshold' (Tsa) does indeed exist. Tsa is the point during exercise at which the levels of salivary alpha-amylase and electrolytes (especially Na+) also begin to rise above baseline levels. The occurrence of the 2 thresholds (AT and Tsa) might, in turn, be attributable to the same underlying mechanism, that of increased adrenal sympathetic activity at high exercise intensities.

Oral microbial ecology and the role of salivary immunoglobulin A

In the oral cavity, indigenous bacteria are often associated with two major oral diseases, caries and periodontal diseases. These diseases seem to appear following an imbalance in the oral resident microbiota, leading to the emergence of potentially pathogenic bacteria. To define the process involved in caries and periodontal diseases, it is necessary to understand the ecology of the oral cavity and to identify the factors responsible for the transition of the oral microbiota from a commensal to a pathogenic relationship with the host. The regulatory forces influencing the oral ecosystem can be divided into three major categories: host related, microbe related, and external factors. Among host factors, secretory immunoglobulin A (SIgA) constitutes the main specific immune defense mechanism in saliva and may play an important role in the homeostasis of the oral microbiota. Naturally occurring SIgA antibodies that are reactive against a variety of indigenous bacteria are detectable in saliva. These antibodies may control the oral microbiota by reducing the adherence of bacteria to the oral mucosa and teeth. It is thought that protection against bacterial etiologic agents of caries and periodontal diseases could be conferred by the induction of SIgA antibodies via the stimulation of the mucosal immune system. However, elucidation of the role of the SIgA immune system in controlling the oral indigenous microbiota is a prerequisite for the development of effective vaccines against these diseases. The role of SIgA antibodies in the acquisition and the regulation of the indigenous microbiota is still controversial. Our review discusses the importance of SIgA among the multiple factors that control the oral microbiota. It describes the oral ecosystems, the principal factors that may control the oral microbiota, a basic knowledge of the secretory immune system, the biological functions of SIgA, and, finally, experiments related to the role of SIgA in oral microbial ecology.

Effect of exercise on milk immunoglobulin A

The major immunoglobulin (Ig) in human secretions is IgA. The immune properties of breast milk are well documented; however, the immunological influence of maximal exercise has not been established. The objective of this study was to investigate the role that exercise has on breast milk IgA and IgA subclasses. Breast milk was collected from 17 lactating women (4.6 +/- 2.3 months postpartum) before and after randomized exercise and control periods. The exercise treatment was a maximal graded treadmill test (VO2max = 30.3 +/- 5.7 mL x min-1 x kg-1). Milk was collected at rest, the breasts were emptied, and samples obtained 10, 30, and 60 min following either exercise or 30-min control rest periods. IgA concentrations were established by enzyme-linked immunosorbent assay. The results indicated that samples taken 10 and 30 min after the exercise period had significantly lower (P < or = 0.05) milk IgA concentrations (21.0 +/- 1.8 and 21.8 +/- 1.4 microg x mL-1, respectively) than the corresponding control resting samples (52.8 +/- 3.5 and 79.3 +/- 7.7 microg x mL-1). The exercise samples were similar to the control samples at 60 min (134.0 +/- 24.6 and 116.0 +/- 15.4 microg x mL-1, respectively), indicating that by 1 h, milk IgA production had recovered. The IgA1 data showed a similar significant decrease (P < or = 0.05) at 10 min postexercise, which also returned to control concentrations by the 30- and 60-min collection intervals. There was no significant change in the milk IgA2 concentrations at any of the time points studied. Milk IgA concentrations increased significantly in both exercise and resting control groups after the breasts were emptied, suggesting that breast emptying stimulated milk IgA synthesis. The results provide evidence that exercise alters milk IgA and IgA1 concentrations for 10-30 min after exhaustive exercise, but recovers by 1 h, and provide additional support for exercise effects on the mucosal immune system.

Salivary levels of immunoglobulin A in triathletes

We investigated whether the physical exercise of an olympic distance triathlon affected the salivary IgA excretion of triathletes, as a biomarker for mucosal immune defence. 42 triathletes participated in the study. It was found that the salivary flow rate was decreased significantly after the race, thereby resulting in a significant reduction of the total salivary IgA output. The salivary IgA concentration (mg IgA/ml) did not differ, but expressed as total salivary protein, a significant reduction was observed. This was on the account of the salivary protein concentration (mg protein/ml), which was significantly increased. In contrast to the IgA secretion, the salivary amylase activity was increased significantly after the race. Therefore, our data suggest that the exercise of a triathlon may decrease the level of IgA-mediated immune protection at the mucosal surface. As triathletes may during the race be exposed to micro-organisms present in the swimming water, a decreased IgA-mediated immunity during the race may pose triathletes at an increased risk of infections.

Saliva and marathon running

The aim of this study was to follow changes in saliva and serum after strenous prolonged exercise. Twenty individuals, three women and 17 men, 24-62 years old, well-trained but not at elite level, participating in the Stockholm Marathon, were selected for the study. Two of the subjects broke the race after 20 km. Three samples of saliva were collected, i.e. (i) just before the race, (ii) directly after the race, and (iii) 1 h after the race. Paraffin-stimulated whole saliva, resting non-stimulated whole saliva and citric acid-stimulated parotid saliva were investigated. In all three types of saliva, there was a decrease in secretion rate and only 14 of the 18 participants could produce resting non-stimulated whole saliva directly after the race. The salivary concentration of chloride, phosphate, potassium, amylase, hexosamine, sialic acid and salivary peroxidase were significantly higher after than before the race. There were no significant changes in salivary pH and buffer capacity. The total protein concentration was increased in all types of saliva after the race. To conclude, there were several changes in the saliva composition just after the marathon, but most of the values were back to baseline after 1 h of rest. However, the values for sodium, calcium, phosphate, salivary peroxidase, amylase and salivary IgA were still elevated 1 h after the race.

Infection in athletes

Coaches and athletic team physicians have provided anecdotal information and case studies to support their beliefs that athletes may be unusually prone to illness during strenuous training or competition. Many athletes, in contrast, believe that physical activity improves their resistance to infectious disease. However, it is generally agreed that the stress of competition may make athletes temporarily more susceptible to infectious illness. A review of the literature shows that upper respiratory tract infections and skin infections are more prevalent in top level athletes than in the general population, particularly during periods of intensive training. Exercise induced changes occur in both the innate and adaptive components of the immune system; however, the relative importance of each component is unknown. Strenuous exertion and contact sports may compromise host defence both by reducing physical protection and by impairing immunosurveillance. Skin lacerations, vigorous sweating and maceration of the dermis impair the defence normally provided by the skin surface. In addition, adverse changes in soluble and cellular components of the immune system can increase susceptibility to infection. Persistence with strenuous training during an infectious illness can have deleterious effects; not only is athletic performance impaired, but the severity of the disease process can be augmented.