CYTOKINE PRODUCTION BY THYMIC ADHERENT CELLS DURING RADIATION-INDUCED THYMIC LYMPHOMAGENESIS

CYTOKINE PRODUCTION BY THYMIC ADHERENT CELLS DURING RADIATION-INDUCED THYMIC LYMPHOMAGENESISAsako Nagayasu1,2, Shizuko Kakinuma2, Mayumi Nishimura2, Izumi Tanaka3, Hiroshi Ishihara3, Yoshiro Kobayashi1, Yoshiya Shimada2(1Dept .Biomol. Sci., Facul. Sci., Toho Univ., 2Low Dose Radiat. Effects Project. NIRS., 3Redox Regul. Res. Group, NIRS)\nCytokines produced by thymic macrophages regulate the normal development of thymocytes. These cytokines are also considered to influence the development of thymic lymphomas. The aim of this study was to elucidate the cytokine production by thymic macrophages during thymic lymphomagenesis. Five-weeks-old female B6 mice were irradiated with whole-body X-rays once a week for 4 consecutive weeks. Onset of thymic lymphoma was detected 12 weeks after the last exposure. The adherent cells isolated from thymi, which consisted of mostly macrophages as determined by phagocytosis of latex beads and staining with F4/80, were examined for cytokine production. It turned out that significant increase in the expression of IL1alpha, IL11, IL12p40 and IL13 was apparent 2 days after each irradiation. Interestingly, re-expression of these cytokines was observed again 2 weeks after the last exposure, when the pre-lymphoma cells appeared. TNFalpha production was significantly reduced 12 weeks after the last exposure, when the onset of neoplastic enlargement of thymi took place. The role of these cytokines in lymphomagenesis will be discussed4th International Workshop of Kyoto T Cell Conferenc