Operation Everest II: Alterations in the Immune System at High Altitude

摘要

The authors investigated the effects of progressive hypobaric hypoxia simulating an ascent to 25,000 ft (7,620m) over 4 weeks on immune function. Multiple simultaneous in vitro and in vivo immunologic parameters were obtained from 7 subjects at sea level, 7,500 ft (2,286m), and 25,000 ft during a decompression chamber exposure. PHA stimulated thymidine uptake and protein synthesis in mononuclear cells were reduced at extreme altitude. An increase in monocytes without changes in B cells or T cell subsets was also observed by flow cytometry analysis. Plasma IgM and IgA but not IgG levels were increased at altitude, whereas PWM stimulated in vitro IgG, IgA and IgM secretion was unchanged. In vitro PHA stimulated interferon production and NK cytotoxicity did not change statistically but large inter-subject differences were observed during exposure to 25,000 ft. Nasal wash IgA and lysozyme levels, and serum antibodies to nuclear antigens were not influenced by altitude exposure. These results suggest that T cell function is blunted during exposure to severe hypoxemia, whereas B cell function and mucosal immunity are not. While the mechanism of altered in vitro immune responsiveness following exposure to various environmental stressors has not been elucidated in humans, hypoxia may induce immune dysfunction as suggested by in vitro immune effector cell function assays.