Stress, suspension and resistance to infection.

Immune function is altered in stressful situations, including space flight. This may result in increased risk of infection. Antiorthostatic suspension has been used to study the effects of space flight-like conditions on immunity. The mechanisms of promoting infection in stressful situations have not been defined, but catecholamines could play a role. In the present study gram negative bacteria grown with catecholamines showed enhanced bacterial growth compared to controls. Additionally, antiorthostatically suspended mice infected with Klebsiella pneumoniae showed decreased survival compared to restrained or normally caged controls. Therefore, stress-induced enhanced bacterial growth and immunosuppression could play a role in suspension-induced enhanced mortality due to infection.