|Budget Amount *help
¥7,200,000 (Direct Cost : ¥7,200,000)
Fiscal Year 1996 : ¥2,700,000 (Direct Cost : ¥2,700,000)
Fiscal Year 1995 : ¥4,500,000 (Direct Cost : ¥4,500,000)
Fas antigen (Fas/CD95) is a cell surface receptor protein that mediates apoptosis-inducing signals. To assess the role of apoptosis mediated by Fas in the development and function of T lymphocytes, we generated transgenic mice overexpreesing murine Fas (mFas) specifically on T cells in the thymus and periphery. These transgenic mice possessed less CD4^+ CD8^+ and CD4^+ CD8^- T cells in the thymus than normal mice, although the numbers of the other thymocytes did not decease. In the periphery, the overexperssed mFas does not enhance the clonal deletion of activated T cells. Thus, overexpressed murine Fas on T cells was shown to play an important role in T cell development in thymus, especially in the differentiation from immature CD4^+ CD8^+ to mature CD4^+ single-positive T cells.
To analyze the function of Fas in vivo, we examined the effects of agonistic anti-Fas antibodies in mice. The intraperitoneal administration of the hamster anti-mouse Fas mAb, RK-8 which induced apoptosis both
in vivo and in vitro, did not kill adult mice, whereas those given the another hamster anti-mouse Fas mAb, Jo2, rapidly die of fulminant hepatitis with hemorrhage. Histological analyzes of mice given RK-8 indicated severe damage of the thymus and moderate damage of the spleen and liver. Most of the thymocytes and some hepatocytes underwent apoptosis within one day of administration. At day 7 after administration, the thymus was atrophied. These in vivo effects of RK-8 were transient ; the thymus was regenerated, and the liver and spleen were apparently normaal one month after injection. These results indiated that functional Fas, which introduces the death signal in vivo, is expresses on thymocytes, CD4-positive splenocytes, and some mouse hepatocytes. Then, anti-Fas mAb RK-8 was administrated into MRL-gld/gld mice, and the autoimmune mice were thoroughly recovered from glomerulonephritis, arthritis, sialadenitis, vasculitis, and lymphoadenoathy. The serum level of autoantibodies were decreased and the all therapeutic effects of RK-8 persisted for over 6 months. These findings suggest that the systemic administration of agonistic anti-Fas antibody is a useful therapeutic strategy for treating systemic autoimmune disease. Less