Fas is type I membrane protein, expressed on various tissue including hematopoietic cell. Its ligand (FasL), a member of the tumor necrosis factor (TNF) family, which includes two forms of a membrane-bound form and a soluble one, induces apoptosis of Fas-bearing cells through cytotoxic activity. FasL is undetectable in the serum of healthy person, whereas it is high in that from patients with T...