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Countermeasure For Space Flight Effects On Immune System: Nutritional Nucleotides   A.D. Kulkarni1, K. Yamauchi1, A. Sundaresan1,2, G.T. Ramesh3, N. R. Pellis41Department of Surgery, Univ. of Texas Health Science Center, 2USRA/NASA, 3Texas Southern University, 4JSC/NASA, Houston.

   Microgravity and its environment have adverse effects on the immune system. We examined the effects of supplemental dietary nucleotides on immune function in ground-based in vivo anti-orthostatic tail-suspended (AOS) mice and in vitro (bioreactor BIO) analogs of microgravity. Methods: BALB/c mice were divided into the following three groups: group housed, single isolation, and AOS. Mice were fed either control chow or chow supplemented with RNA or Uracil. Immune function was assessed by in vivo popliteal lymph node proliferation (PLN), in vitro phytohemagglutinin (PHA)-stimulated proliferation of splenocytes and cytokine production. BIO splenocytes were cultured in vitro with/without PHA, a nucleoside/nucleotide mixture (NS/NT) or uridine. The cell proliferation and cytokine assays were carried out. Results: PLN response was significantly suppressed in AOS mice (P<0.05) and was restored by RNA and Uracil supplemented diets. Splenocytes from AOS mice had decreased PHA stimulated proliferation, decreased IL-2 and IFN-g cytokine levels (P<0.05). These responses were restored by RNA and Uracil diets. In BIO cultures, PHA response was suppressed significantly, and Uridine and NS/NT restored the proliferative responses. Mechanisms of immune restoration in microgravity analogs, including CNS mediated effects and their implications for addressing the NASA's CRP and CRL maps in areas of nutrition and immunology areas will be presented.  Conclusion: In the microgravity analog environment of AOS and BIO, supplemental nucleotides and especially Uracil/Uridine have up-regulating and immunoprotective effects with potential as a countermeasure to the observed immune dysfunction in true microgravity.(Supported by NASA-NCC-8-168)