Exposure of humans to space flight conditions results in immune responses. The contribution of these changes in the immune system to alterations in resistance to infection and tumors remains to be fully established. The head down tilt bed rest model has been established as valid for studying the effects of space flight conditions on functional dynamic immune responses such as cytokine production. The proposed study is designed to determine the effects of bed rest on immune responses of subjects. The overall hypothesis to be tested is: maintenance of subjects in the head down tilt bed rest model will result in suppression of functional immune responses and enhance susceptibility to infection. The specific aims of the proposed study are: to determine the effects of maintenance of subjects in the head down tilt bed rest model on functional immune responses, and resistance to infection. The effects of bed rest on immune function and control of viral infections will be correlated to space flight.
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Blood, urine and saliva samples were obtained from bed rest subjects prior to, at intervals during, and after completion of 60 days of head-down tilt bed rest. Leukocyte blastogenesis, cytokine production and virus reactivation were assessed. The ability of the subjects to respond appropriately to immunization with the neoantigen bacteriophage fX-174 was also determined.
Blood cells from three male subjects were challenged with either concanavalin A (a mitogen that stimulates T-lymphocyte division) or lipopolysaccharide (a mitogen that stimulates B lymphocyte division). After incubation, tritiated thymidine was added to the cells, and enhanced incorporation is an indication of lymphocyte blastogenesis. Urine samples were assayed for the presence of human polyomavirus gene sequences.
Over the course of bed rest, concanavalin A-induced T cell blastogenesis appeared to change. The change began immediately after the start of bed rest, and persisted throughout bed rest. Values returned to normal after bed rest.
Lipopopolysaccharide-induced B cell blastogenesis appeared to follow a similar pattern. One subject excreted polyomavirus JCV in each of eight urine samples. The amount of virus fluctuated from one collection to the next, and there was no correlation between duration of bedrest and the viral load to the urine.
Shearer, W.T., Ochs, H.D., Lee, B.N., Cohen, E.N., Reuben, J.M., Cheng, I., Thompson, B., Butel, J.S., Blancher, A., Abbal, M., Aviles, H., Sonnenfeld, G. Immune responses in adult female volunteers during bed-rest model of space flight: antibodies and cytokines. J. Allergy Clin. Immunol.
123, 900-905, 2009.[
Sonnenfeld G, Avilesa H, Butel JS, Shearer WT, Nieself D, Pandyaf U, Allen C, Ochsg HD, Blancher A, Abbal M.
Bed Rest and Immunity. Acta Astronautica
Volume 60, Issues 4-7, February-April 2007, Pages 234-236.
Herpesvirus 3, human/physiology
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Crew health and performance is critical to successful human exploration beyond low Earth orbit.
The Human Research Program (HRP) investigates and mitigates the highest risks to human health
and performance, providing essential countermeasures and technologies for human space exploration.
Risks include physiological and performance effects from hazards such as radiation, altered gravity,
and hostile environments, as well as unique challenges in medical support, human factors,
and behavioral health support. The HRP utilizes an Integrated Research Plan (IRP) to identify
the approach and research activities planned to address these risks, which are assigned to specific
Elements within the program. The Human Research Roadmap is the web-based tool for communicating the IRP content.
The Human Research Roadmap is located at: https://humanresearchroadmap.nasa.gov/
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