Spaceflight effects on T lymphocyte distribution, function and gene expression

Gridley DS, Slater JM, Luo-Owen X, Rizvi A, Chapes SK, Stodieck LS, Ferguson VL, Pecaut MJ. Spaceflight effects on T lymphocyte distribution, function and gene expression. J Appl Physiol 106: 194-202, 2009. First published November 6, 2008; doi: 10.1152/japplphysiol.91126.2008.-The immune system is highly sensitive to stressors present during spaceflight. The major emphasis of this study was on the T lymphocytes in C57BL/6NTac mice after return from a 13-day space shuttle mission (STS-118). Spleens and thymuses from flight animals (FLT) and ground controls similarly housed in animal enclosure modules (AEM) were evaluated within 3-6 h after landing. Phytohemagglutinin-induced splenocyte DNA synthesis was significantly reduced in FLT mice when based on both counts per minute and stimulation indexes ( P < 0.05). Flow cytometry showed that CD3(+) T and CD19(+) B cell counts were low in spleens from the FLT group, whereas the number of NK1.1(+) natural killer (NK) cells was increased ( P < 0.01 for all three populations vs. AEM). The numerical changes resulted in a low percentage of T cells and high percentage of NK cells in FLT animals ( P < 0.05). After activation of spleen cells with anti-CD3 monoclonal antibody, interleukin-2 (IL-2) was decreased, but IL-10, interferon-gamma, and macrophage inflammatory protein-1 alpha were increased in FLT mice ( P < 0.05). Analysis of cancer-related genes in the thymus showed that the expression of 30 of 84 genes was significantly affected by flight ( P < 0.05). Genes that differed from AEM controls by at least 1.5-fold were Birc5, Figf, Grb2, and Tert (upregulated) and Fos, Ifnb1, Itgb3, Mmp9, Myc, Pdgfb, S100a4, Thbs, and Tnf (downregulated). Collectively, the data show that T cell distribution, function, and gene expression are significantly modified shortly after return from the spaceflight environment.