Salivary immunoglobulin A (sIgA) as a biomarker of immune suppression following the combat fitness assessment

SIgA is a potential biomarker for stress. The usual day-to-day and within day variation in sIgA amongst a group of healthy Army reservists was estimated and the acute response of sIgA to moderate intensity exercise (Combat Fitness Assessment) undertaken in both cool-dry and hot-humid conditions was determined. The results indicate that thermal and cardiovascular strain resulting from moderate intensity exercise in hot-humid conditions suppresses sIgA for at least 24 hours post-exercise. Salivary sIgA exhibits a wide biological variation which casts some doubt on its usefulness as a biomarker, however because sIgA has been shown to be sensitive to dietary restriction, alcohol consumption, loss of body mass, fatigue and negative emotions in previous studies and now heat-induced cardiovascular strain, further work is warranted to develop this biomarker.