title: 21 Days head-down bed rest induces weakening of cell-mediated immunity - Some spaceflight findings confirmed in a ground-based analog.
abstract: Several studies indicate a weakening of cell-mediated immunity (CMI) and reactivation of latent herpes viruses during spaceflight. We tested the hypothesis that head-down bed rest (HDBR), a ground-based analog of spaceflight, mimics the impact of microgravity on human immunity. Seven healthy young males underwent two periods of 3 weeks HDBR in the test facility of the German Aerospace Center. As a nutritional countermeasure aimed against bone demineralisation, 90 mmol potassium bicarbonate (KHCO(3)) was administered daily in a crossover design. Blood samples were drawn on five occasions. Whole blood was stimulated with antigen i.e. Candida albicans, purified protein derivative (PPD) tuberculin, tetanus toxoid and Cytomegalovirus (CMV) (CMV-QuantiFERON). Flow cytometric analysis included CD4(+)CD25(+)CD127(-)FOXP3(+) regulatory T cells (Tregs), γδ T cells, B cells, NK cells and dendritic cells. In one of the two bed rest periods, we observed a significant decrease in production of interleukin-2 (IL-2), interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) following phytohemagglutinin (PHA) stimulation, with a rapid normalization being observed after HDBR. The cytokine levels showed a V-shaped pattern that led to a relativeTh2-shift in cytokine balance. Only three individuals responded to the specific T cell antigens without showing signs of an altered response during HDBR, nor did we observe reactivation of CMV or Epstein-Barr virus (EBV). Of unknown significance, dietary supplementation with KHCO(3) counteracted the decrease in IL-2 levels during HDBR, while there was no impact on other immunological parameters. We conclude that discrete alterations in CMI may be induced by HDBR in selected individuals.
authors.affiliation: Department of Medicine, Randers Regional Hospital, Denmark. jenskels@rm.dk
authors.forename: Jens
authors.initials: J
authors.lastname: Kelsen
authors.forename: Lars Erik
authors.initials: LE
authors.lastname: Bartels
authors.forename: Anders
authors.initials: A
authors.lastname: Dige
authors.forename: Christian Lodberg
authors.initials: CL
authors.lastname: Hvas
authors.forename: Petra
authors.initials: P
authors.lastname: Frings-Meuthen
authors.forename: Gisela
authors.initials: G
authors.lastname: Boehme
authors.forename: Marianne Kragh
authors.initials: MK
authors.lastname: Thomsen
authors.forename: Morten
authors.initials: M
authors.lastname: Fenger-Grøn
authors.forename: Jens Frederik
authors.initials: JF
authors.lastname: Dahlerup
mesh_terms: D000328:Adult; D001510:Bed Rest; D003141:Communicable Diseases / Q000453:epidemiology; D018592:Cross-Over Studies; D016207:Cytokines / Q000276:immunology; D000939:Epitopes / Q000276:immunology; D005434:Flow Cytometry; D005858:Germany / Q000453:epidemiology; D018475:Head-Down Tilt / Q000502:physiology*; D006801:Humans; D007111:Immunity, Cellular / Q000187:drug effects / Q000276:immunology*; D015994:Incidence; D008297:Male; D009747:Nutritional Physiological Phenomena / Q000187:drug effects; D010835:Phytohemagglutinins / Q000494:pharmacology; D015203:Reproducibility of Results; D013026:Space Flight; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology; D013997:Time Factors; D014780:Viruses / Q000187:drug effects / Q000276:immunology; D018544:Weightlessness Countermeasures; D018474:Weightlessness Simulation / Q000009:adverse effects*
chemical_list: D016207:Cytokines; D000939:Epitopes; D010835:Phytohemagglutinins