Fas ligand, also known as FASLG, belongs to the tumor necrosis factor family and is the ligand for FAS. Both are transmembrane proteins. Interaction of FAS with this ligand is critical in triggering apoptosis of some types of cells such as lymphocytes. Defects in FASLG may be related to some cases of systemic lupus erythematosus (SLE). Recombinant human FASLG protein, fused to His-tag at N-terminus, was expressed in E.coli.