Expanded CD3+TcRαβ+CD4-CD8- double negative T-cells (DNT) are a hallmark of ALPS patients who can also present elevated plasma biomarkers including interleukin-10 (IL-10), soluble FasL (sFasL) (diminished in patients with defect in FASL) and vitamin B12 (9). Here, FASLG is linked to autoimmune lymphoproliferative syndrome.