However, none of the ALPS patient cases has shown to have germline homozygous or heterozygous mutations in the E163 and E271 of FASLG. Based on our His-tagged FasL and tandem FasL studies, it is evident that both E163 and E271 are highly dominant mutations that totally abolish the Fas cytotoxic signaling. This evidence concerns the gene FASLG and autoimmune lymphoproliferative syndrome.