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Clinical and Vaccine Immunology, October 2008, p. 1523-1528, Vol. 15, No. 10
1071-412X/08/$08.00+0 doi:10.1128/CVI.00065-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Enterprise Advisory Services Inc., Houston, Texas,1 Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts,2 School of Public Health, University of Texas Health Science Center, Houston, Texas,3 NASA Johnson Space Center, Houston, Texas4
Received 5 February 2008/ Returned for modification 28 March 2008/ Accepted 21 August 2008
Astronauts live and work in relatively crowded, confined environments on the Space Shuttle and the International Space Station. They experience a unique set of stressors that contribute to a diminishment of many immune responses. This study investigated the ability of the shuttle crew members' monocytes to respond to gram-negative endotoxin that they could encounter during infections. Blood specimens were collected from 20 crew members and 15 control subjects 10 days before launch, 3 to 4 h after landing, and 15 days after landing and from crew members during their annual medical examination at 6 to 12 months after landing. When challenged with gram-negative endotoxin, the crew member's monocytes collected at all three time points produced lower levels of interleukin-6 (IL-6) and IL-1β and higher levels of IL-1ra and IL-8 compared to those of control subjects. Cytokines were assessed by measuring the number of cells positive for intracellular cytokines. These values returned to normal 6 to 12 months after landing, except for IL-1ra, which was still higher (five- to sixfold) than in controls. This phenomenon was accompanied by an increased expression of Toll-like receptor 4 and decreased expression of CD14 on the crew members' monocytes at all time points. There were also increased levels of the lipopolysaccharide binding protein in the plasma of the crew members 3 to 4 h and 15 days after landing. This study shows that spaceflight-associated factors (in-flight and preflight) modulate the response of monocytes to gram-negative endotoxins.
Published ahead of print on 3 September 2008.
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