[48]

Space Flight Microgravity and Ground Proton Irradiation Induce an Immune Response and Tumorigenesis in the Fruit Fly, Drosophila melanogaster.  S. Bhattacharya¹, M.E. Sanchez², M. Lera³, L. Higgins¹, E. Blazevic³ and O. Marcu^{1       1}NASA Ames Research Center, ²Lockheed Martin Mission Services, ³NASA Ames Internship Program, Moffett Field, CA.

   Microgravity and radiation are two components of the space flight environment that have implications for human space exploration.  We addressed the effects of microgravity on immunity and tumor formation using the fruit fly, D. melanogaster aboard STS-121 and the effects of exposure to proton radiation in ground experiments at Loma Linda University Medical Center.  The fruit fly immunity is a model for the human innate response and allows for genetic manipulation to understand the cellular and molecular mechanism of immunity in space.  Microgravity conditions resulted in slower development, increased lethality and melanization, as general stress responses.  A very specific response was the reduced cellular immunity, reflected by a decrease in the number of blood cells in flight specimens compared to ground controls, paralleled by a reduction in the phagocytic activity at larval stages of development.  However, the humoral component of the immune response, driven by the production of antibacterial peptides, supported a general increased defense against bacterial infection.  We are currently quantifying the expression of the relevant pathways in flight vs ground samples. 

   Radiation in the space environment includes protons from galactic cosmic rays and solar events.  Proton irradiation on ground increased the incidence of melanotic tumors in the fruit fly model of human leukemia, in a dose-dependent manner.  Tumorigenesis is likely associated with blood cell differentiation and involves the Jak/STAT pathway, a modulator of cytokine signaling.  We are using the fruit fly model as a convenient tool for screening for countermeasures for radiation-induced tumors and for determining the combined effect of microgravity and radiation.

(Supported by NASA: FIT - Fly/Fungal Immunity and Tumorigenesis)