title: Microgravity inhibits resting T cell immunity in an exposure time-dependent manner.
abstract: BACKGROUND
  Decline immune function is well documented after spaceflights. Microgravity is one of the key factors directly suppressing the function of immune system. Though T cell immune response was inhibited by microgravity, it is not clearly whether activation would be inhibited after a pre-exposure of microgravity on T lymphocytes at the resting state.
  
  
  METHODS
  We herein investigated the response ability of resting CD4⁺ and CD8⁺ T cells experiencing pre-exposure of modeled microgravity (MMg) for 0, 8, 16 and 24 hrs to concanavalin A (ConA) stimulation. The phenotypes and subsets of immune cells were determined by flow cytometry.
  
  
  RESULTS
  Both CD4⁺ and CD8⁺ T cells with an MMg pre-exposure exhibited decreased expressions of activation-markers including CD25, CD69 and CD71, inflammatory cytokine secretion and cell proliferation in response to ConA compared with T cells with 1g controls in an MMg exposure time- dependent manner. Moreover, short term MMg treatment caused more severe decreased proliferation in CD4⁺ T cells than in CD8⁺ T cells.
  
  
  CONCLUSIONS
  MMg can directly impact on resting T cell subsets. CD4⁺ T cells were more sensitive to the microgravity inhibition than CD8⁺ T cells in respect of cell proliferation. These results offered new insights for the MMg-caused T cell functional defects.
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Haiying
authors.initials: H
authors.lastname: Luo
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Chongzhen
authors.initials: C
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Meifu
authors.initials: M
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D049109:Cell Proliferation / Q000187:drug effects; D003208:Concanavalin A / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D013997:Time Factors; D014893:Weightlessness / Q000009:adverse effects*
chemical_list: D016207:Cytokines; D003208:Concanavalin A
keywords: Immune response; T cells; microgravity; proliferation; spaceflight.