May play a role in the immune system processes. Protects cells from FAS-, TNF alpha- and FADD-induced apoptosis without increasing expression of the inhibitors of apoptosis BCL2 and BCLXL. Seems to activate an inhibitory pathway that prevents CASP8 activation following FAS stimulation, rather than blocking apoptotic signals downstream. May inhibit FAS-induced apoptosis by preventing CASP8 processing through CFLAR up-regulation. Detected in the serum. Expressed in lymph nodes, peripheral blood leukocytes, lung, thymus and kidneys. Very weak expression detected in spleen, liver, heart, and salivary gland. Expressed in lymphoid cell lines such as Jurkat, CEM-T4, MOLT-4, HB11;19 and Reh. No expression detected in nonhematopoietic cell lines including Hep-G2, HEK293 and HeLa. Detected at high levels in chronic lymphocytic leukemia cells. By T-cell activation. The Ig-like domain is required for the anti-apoptotic ability. 'Toso' is a Japanese liquor drunk on New Year's day to celebrate long life and eternal youth.