FAS and autoimmune lymphoproliferative syndrome: Mutations in the gene encoding the TNF-family receptor Fas (CD95, TNFRSF6) have been linked to autoimmunity for more than 20 years through the discovery of dominant-negative mutations in Fas in autoimmune lymphoproliferative syndrome (ALPS, MIM 601859) and a retrotransposon insertion disrupting Fas expression in the lpr mouse strain3, 4, 5, 6.