Secondly, somatic mutations feature prominently in the interface, whether in ALPS patients with somatic FAS mutations (largely confined to DNT cells), TLR8-GOF patients (multiple cell lineages consistent with a pluripotent stem cell origin), or patients with somatic STAT3 (and in certain cases, STAT5b) in LGL cells from T-LGLL patients (16, 32, 33, 39). The gene discussed is STAT3; the disease is T-cell large granular lymphocyte leukemia.