INFLUENCE OF SPACEFLIGHT ON THE PRODUCTION OF INTERLEUKIN-3 AND INTERLEUKIN-6 BY RAT SPLEEN AND THYMUS-CELLS

Six adult male Sprague-Dawley rats were flown on the 7-day US space sh uttle mission STS-54. After flight, the spleen and thymus from each an imal were assayed for the capacity to secrete the cytokines interleuki n-3 (IL-3) and IL-6. Spleen and thymus cells (5 X 10(6)/ml) were incub ated for 48 h in the presence of 5 mu g/ml of concanavalin A or 2 mu g /ml of bacterial lipopolysaccharide to stimulate the production of IL- 3 and IL-6. IL-3 activity was measured using the IL-3/colony-stimulati ng-factor-dependent cell line 32D. IL-6 activity was measured using th e IL-6-dependent cell line 7TD1. Spleen and thymus cells harvested fro m flown rats secreted significantly higher titers of biologically acti ve IL-3 compared with ground control rats. Spaceflight significantly e nhanced IL-6 production by thymus, but not spleen, cells. The results of this study demonstrate that spaceflight can enhance the production of certain cytokines by cells of the immune system.