Toso, also known as Fas Apoptotic Inhibitory Molecule 3 (FAIM3). Toso is expressed by lymphoid and hematopoietic cells and is up-regulated by T-cell activation. Toso expressing cells have increased resistance to Fas-, FADD-, and TNFalpha-induced apoptosis. Toso is membrane bound, and is thought to directly bind to FADD, disrupting DISC formation and thus inhibiting caspase-8 activation. Toso is a potential proto-oncogene, and could be a therapeutic target for use in the treatment of autoimmune diseases. Despite its predicted molecular weight, Toso often migrates at 60kD in SDS PAGE.