Radiation combined with thermal injury: induction of a radio-resistant immature myeloid cell. (118.10)

Abstract

Abstract Increasing sophistication of terrorist attacks and recent nuclear energy crises have amplified the interest in the immunobiology of radiation combined with burn injury (RCI). Burn is associated with immunosuppression and increased mortality with lower doses of ionizing radiation. We hypothesize that RCI results in reduction of immune cell populations with a decrease in serum cytokine levels. C57BL/6 female mice underwent either a 20% TBSA full thickness contact burn or sham procedure. One burn group and one sham group received a single whole body dose of 5 Gy gamma radiation. Spleens and burn draining lymph nodes (dLN) were harvested 3 and 14 days later. Flow cytometry was performed to identify adaptive and innate cells. Serum was analyzed by multiplex bead array assay. IL-1β (day3), MCP-1 and IP-10 (days 3 and 14) were significantly elevated in RCI mice when compared to all other groups. At day 14, splenic and dLN T-cells, B-cells and neutrophils were significantly decreased after irradiation and RCI when compared to sham and burn alone. In contrast, numbers and percentages of Gr.1+CD11b+ cells were significantly increased. We confirmed these were not myeloid-derived suppressor cells as they did not suppress T cell proliferation in vitro. These data suggest that while RCI depletes immune cells, there are specific cytokine alterations and induction of a population of immature myeloid-derived cells which may act as a potential target for immune countermeasures.