MRL-lpr/lpr mice bear mutations in the gene encoding Fas and serve as a widely used model for autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjögren’s syndrome (SS), and autoimmune lymphoproliferation syndrome (ALPS) (10, 11). Here, FAS is linked to autoimmune lymphoproliferative syndrome.