Respiratory infection risk in athletes: association with antigen‐stimulated IL‐10 production and salivary IgA secretion

Abstract

The purpose of this study was to examine factors influencing susceptibility to upper respiratory tract infections (URTI) in 18-35-year-old men and women engaged in endurance-based physical activity during the winter months. Eighty individuals (46 males, 34 females) provided resting blood and saliva samples for determination of markers of systemic immunity. Weekly training and illness logs were kept for the following 4 months. Thirty subjects did not experience an URTI episode and 24 subjects experienced 3 or more weeks of URTI symptoms. These illness-prone subjects had higher training loads and had ∼2.5-fold higher interleukin (IL)-4 and IL-10 production by antigen-stimulated whole blood culture than the illness-free subjects. Illness-prone subjects also had significantly lower saliva S-IgA secretion rate and higher plasma IgM (but not IgA or IgG) concentration than the illness-free subjects. There were no differences in circulating numbers of leukocyte subtypes or lymphocyte subsets between the illness-prone and illness-free subjects. The production of IL-10 was positively correlated and the S-IgA secretion rate was negatively correlated with the number of weeks with infection symptoms. It is concluded that high IL-10 production in response to antigen challenge and low S-IgA secretion are risk factors for development of URTI in physically active individuals.

The influence of exercise training status on antigen-stimulated IL-10 production in whole blood culture and numbers of circulating regulatory T cells

“…More recently, elevations in antigen-stimulated whole blood IL-10 production have been reported in individuals engaged in high levels (~14 h/week) of moderate-vigorous endurance exercise compared with those performing relatively moderate (~5 h/week) training loads (Gleeson et al 2012). In addition to this, the authors also highlighted a significantly higher incidence of URTI episodes in those individuals performing higher training loads.…”

“…Observations from the athletic population have given support to these findings, with high training loads (Gleeson et al 2012;Nieman 1990) and intensified periods of training (Fahlman and Engels 2005) reported to be associated with a higher incidence of URTI.…”

“…From its conception in the early 1990s, the 'J' shaped curve has commonly been used to express the association between habitual physical activity level and risk of upper respiratory tract infection (URTI) (Gleeson et al 2012;Matthews et al 2002;Nieman 1994). Defined within this relationship, regular moderate exercise is seen to enhance immunosurveillance and immune function (Nieman 2000), in turn reducing the risk of such infections.…”

“…interleukin (IL)-10 and IL-4 production) may be also involved in driving this relationship (Gleeson et al 2012;Wang et al 2012). …”

Fitness level impacts salivary antimicrobial protein responses to a single bout of cycling exercise

“…Indeed, periods of intense, frequent, endurance--based training have consistently been associated with self--reported symptoms of URTI in elite--level athletes (Gleeson 2000;Gleeson and Pyne 2000;Nieman 2000). Low levels of salivary secretory Immunoglubulin A (SIgA) have been linked with an increased risk of URTI (Fahlman and Engels 2005;Gleeson et al 2012;Hanson et al 1983;Neville et al 2008) and prolonged, high--intensity exercise bouts lower both the concentration and secretion of salivary SIgA (Fahlman et al 2001;Nieman et al 2006;Steerenberg et al 1997;Tomasi et al 1982;Usui et al 2011). On the other hand, shorter exercise bouts, or low to moderate--intensity exercise, may actually increase salivary SIgA concentration and secretion (Allgrove et al 2008;Li and Gleeson 2004), indicating that mucosal immune integrity, and indeed URTI risk, is dependent on the duration and intensity of the exercise performed.…”