Effect of Bed Rest with Amino Acid Supplementation on Cell-Mediated Immune Response in Healthy Men: Indications for Immune Status of Astronauts

Space flight can induce changes in human physiological systems including adverse effects on immune function. Due to enormous variability in flight conditions and restricted access to space flights, there is a lack of reproducible data and consistent results. Microgravity is one of the causes implicated in the deterioration of the immune response after space flight. In this human study, we used bed rest (BR) to simulate the effects of microgravity and weightlessness experienced in space on cell-mediated immune response. Healthy men aged 30–55 y were randomized into a timed feeding (AA, N=7, used as control) and two experimental groups: resistance training (RT, N=12) and AART (N=12). All men received an essential amino acid supplement and were subjected to 28 days of strict bed rest and 14 days of recovery. The RT and AART groups received resistance training with different supplement feeding times (RT-3 hrs post exercise, AART-5 minutes pre exercise). There were no statistically significant time or time∗group effects on delayed-type hypersensitivity (DTH) response after BR. Similarly, there were no significant differences in changes in lymphocyte proliferation between groups after BR or after recovery. This model of weightlessness did not result in blunted immune response in this subject population. Supported by USDA contract # 58-1950-9-001, NSBRI-NPFR00301, GCRC M01 RR000054.