THE FAS DEATH FACTOR

Fas ligand (FasL), a cell surface molecule belonging to the tumor necr osis factor family, binds to its receptor Fas, thus inducing apoptosis of Fas-bearing cells. Various cells express Fas, whereas FasL is expr essed predominantly in activated T cells. In the immune system, Fas an d Fast are involved in down-regulation of immune reactions as well as in T cell-mediated cytotoxicity. Malfunction of the Fas system causes lymphoproliferative disorders and accelerates autoimmune diseases, whe reas its exacerbation may cause tissue destruction.