MECHANISMS OF IMMUNOSUPPRESSION IN MODELED MICROGRAVITY

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The major goal of this project is to elucidate the mechanisms of immune suppression induced by exposure to the environment of modeled microgravity. Extreme environments, whether of elevated temperatures, high pressure, or extreme cold, have received much attention in the past years due to the myriad living organisms that have been found under those conditions. The study of the adaptations of these organisms to their environment has provided important information for the understanding of our own basic physiological processes. A new extreme environment was unveiled when spaceflight put humans and animals in weightlessness for extended periods of time. Important physiological changes, some of considerable importance to survival, occurred in zero gravity. Immune suppression was one of them. This is manifested by a decrease in T cell proliferation and a reduced response to mitogens. The mechanisms responsible for this effect are unknown. Any instance of immune suppresssion during spaceflight puts severe constraints on the length of exposure, on the capabilities of the crew, on the resources necessary for possible containment of areas or personnel, in short, on the success of any mission involving more than a few days in space. Studies performed in vitro on the space shuttle have revealed that lymphocytes exhibit important changes in their cytoskeletal properties, which suggests that T cell activation may be compromised at the level of the T cell receptor interaction. We thus hypothesize that immunosuppresion produced in weightlessness is due to impaired T cell receptor activation due to cytoskeletal disruption. We propose to evaluate this hypothesis using T cell cultures in modeled microgravity, which is an acceptable substitute of weightlessness at normal gravity. The Specific Aims are 1: Determine the effects of modeled microgravity on T cell activation and Ca+2 signaling in the human lymphoblastoid T cell lines Jurkat and CEM, using intracellular Ca+2 measurement with fura-2. 2: Determine the effects of modeled microgravity on the expression and phosphorylation state of signaling proteins, using immunoprecipitation and Western blotting 3: Evaluate the disruption and reorganization of the T cell cytoskeleton observed during microgravity using immunofluorescence microscopy and immunoprecipitation and Western blotting. This study will provide useful information on the properties of T cell activation in microgravity that will increase our understanding of the basic molecular mechanisms underlying immune function both at normal and low gravity. It will also improve our capabilities for the treatment of immunosuppressive disorders.