Effects of combined stress during intense training on cellular immunity, hormones and respiratory infections.
OBJECTIVE
This study was designed to determine immune and hormonal changes and their relationship with the incidence of upper respiratory tract infections (URTIs) during an extremely stressful military training (3 weeks of physical conditioning followed by a 5-day combat course with energy restriction, sleep deprivation and psychological stress).


METHODS
Blood samples were collected from 21 cadets (21 +/- 2 years old) before training and after the combat course for analysis of leukocyte and lymphocyte subpopulations, serum cytokines [interleukin-6 (IL-6), IL-1beta and IL-10], and hormones [catecholamines, cortisol, leptin, total insulin-like growth factor I (IGF-I), prolactin, dehydroepiandrosterone sulfate (DHEAS) and testosterone]. Symptoms of URTI were recorded from health logs and medical examinations during training.


RESULTS
After the combat course, total leukocyte and neutrophil counts were significantly increased while total lymphocytes were unchanged. In lymphocyte subsets, NK cells were reduced (p < 0.01), while CD4+ and CD19+ (B) cells were increased. Levels of IL-6 were increased (p < 0.01), while those of IL-1beta and IL-10 were unchanged. Norepinephrine and dopamine levels were increased, while those of cortisol were reduced. Levels of leptin, testosterone, prolactin and total IGF-I were reduced, while those of DHEAS were increased. The incidence of URTI increased during the training (chi(2) = 53.48, p < 0.05). After training data analysis showed a significant correlation between URTIs and NK cells (p = 0.0023). Training-induced changes in immune and hormonal parameters were correlated.


CONCLUSIONS
Blood NK cell levels are related to increased respiratory infections during physical training in a multistressor environment. The training-induced decreases in immunostimulatory hormone levels may have triggered immunosuppression.
Gomez-Merino
Danielle
D
Department of Physiology, IMASSA, Brétigny-sur-Orge, France. dgomez@imassa.fr
Drogou
Catherine
C
Chennaoui
Mounir
M
Tiollier
Eve
E
Mathieu
Jacques
J
Guezennec
Charles Yannick
CY
D000328:Adult; D016175:B-Lymphocyte Subsets / Q000276:immunology; D031204:Caloric Restriction / Q000523:psychology; D002395:Catecholamines / Q000097:blood / Q000276:immunology / Q000378:metabolism; D016207:Cytokines / Q000097:blood / Q000276:immunology / Q000378:metabolism; D015536:Down-Regulation / Q000276:immunology; D006728:Hormones / Q000097:blood / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000276:immunology / Q000378:metabolism; D007030:Hypothalamo-Hypophyseal System / Q000276:immunology / Q000378:metabolism; D007108:Immune Tolerance / Q000276:immunology*; D007111:Immunity, Cellular / Q000276:immunology; D007694:Killer Cells, Natural / Q000276:immunology; D008297:Male; D008889:Military Personnel; D015213:Neuroimmunomodulation / Q000276:immunology; D005082:Physical Exertion / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology* / Q000523:psychology; D012141:Respiratory Tract Infections / Q000097:blood / Q000276:immunology* / Q000523:psychology; D012892:Sleep Deprivation / Q000276:immunology; D013312:Stress, Physiological / Q000097:blood / Q000150:complications* / Q000276:immunology*; D013315:Stress, Psychological / Q000276:immunology; D015854:Up-Regulation / Q000276:immunology
D002395:Catecholamines; D016207:Cytokines; D006728:Hormones; D006854:Hydrocortisone