Takehiro Yatomi

Essential roles of the Fas-Fas ligand pathway in the development of pulmonary fibrosis.

The Fas ligand is predominantly expressed in activated T lymphocytes and is one of the major effector molecules of cytotoxic T lymphocytes and natural killer cells. Previously, we found excessive apoptosis of epithelial cells and infiltrating lymphocytes expressing Fas ligand mRNA in the lung tissue of bleomycin-induced pulmonary fibrosis in mice. Here we demonstrated that the administration of a soluble form of Fas antigen or anti-Fas ligand antibody prevented the development of this model and that lpr and gld mice were resistant against the induction of pneumopathy. These results suggest that the Fas-Fas ligand pathway plays an essential role in the development of pulmonary fibrosis and that preventing this pathway could have therapeutic value in lung injury and fibrosis.

Acute Toxicity of an Anti-Fas Antibody in Mice

By histopathologic examination of various organs in 3 normal strains, C3H/HeN, ICR, and DBA/1J, of mice treated intravenously once with anti-Fas antibody (Jo2), we failed to determine any target organ, except the liver, responsible for the acute lethality induced by the Fas/anti-Fas antibody interaction. However, we could show the presence of Fas-mediated apoptosis in other organs aside from the liver and normal mouse strain differences in susceptibility to anti-Fas antibody. Among these strains, C3H/HeN was the most susceptible to the antibody, followed by ICR and DBA/1J. We observed Fas-mediated apoptosis in the liver, spleen, thymus, lymph nodes, Peyers patch, intestine, skin, coagulation glands, ovary, uterus, and vagina in all 3 strains and additionally in the epididymides and seminal vesicles in the DBA/1J strain. We also demonstrated that Fas-mediated apoptosis of small lymphocytes in the mantle zone of splenic lymphatic follicles preceded that of the hepatocytes or thymic cells. Since cellular damage was most severe in the liver among all the apoptotic organs in the 3 mouse strains, liver injury induced by anti-Fas antibody is speculated to play a significant role in the death.

Serum levels of soluble Fas ligand in patients with acute and fulminant hepatitis : relationship with soluble Fas, tumor necrosis factor α and TNF receptor-1

We measured the serum levels of soluble Fas ligand (sFasL) using a newly developed ELISA system in patients with acute hepatitis (AH), acute severe hepatitis (ASH) and fulminant hepatitis (FH). In addition, we also evaluated the relationship between the serum levels of sFasL, soluble Fas (sFas), soluble tumor necrosis factor α (sTNFα), and soluble TNF receptor-1 (sTNFR1). The median serum sFasL level was significantly increased in patients with acute liver disease compared to that in normal subjects; however, there were no significant differences among patients with AH, ASH, and FH. The serum sFasL levels varied according to the cause of hepatitis and were particularly high in patients with hepatitis A viral infection. On the other hand, the median serum sFas level was also significantly increased in patients with acute liver disease compared to that in normal subjects; however, there were no significant differences among patients with the three clinical forms or various causes of hepatitis. The serum sFasL levels decreased rapidly following improvement in liver functions, whereas the serum sFas levels decreased more gradually and remained abnormally high even at follow-up. The serum sFasL levels were not correlated with the levels of serum transaminases or sFas, but were significantly correlated with those of sTNFα (r=0.483, P<0.001) and sTNFR1 (r=0.324, P<0.05). On the other hand, serum sFas levels were significantly correlated with those of sTNFR1 (r=0.319, P<0.05) alone. Our results suggest that the serum sFasL level increases in the acute phase of hepatitis and the level varies according to the cause of hepatitis. Our findings also suggest that the Fas-FasL system and cytokine networks may be closely associated with early process of hepatic necrosis.

Lack of Correlation Between Clinical Characteristics and Serum Soluble Fas Ligand Levels in Patients with Multiple Myeloma

Multiple myeloma is characterized by the accumulation of malignant plasma cells in the bone marrow and rarely cured by chemotherapy. Villunger et al. showed that the neoplastic plasma cells express Fas ligand (FasL), which transmits a signal of apoptosis upon ligation to Fas, and suggested that the FasL suppresses the T-cells activated against malignant cells, resulting in escape from tumour immunity. We examined serum soluble FasL (sFasL) levels in 35 multiple myeloma patients to evaluate the correlation between sFasL levels and clinical characteristics. The serum sFasL levels were not affected by the disease status, serum monoclonal protein levels, or other prognostic factors. We could not determine whether the expression of FasL is involved in the poor clinical course of the disease.