Since leukemic T-LGL are able to spontaneously produce INF-γ and to secrete TNF-α upon stimulation, a cytokine-related increase of Fas expression on CD34+ BM precursors is likely to occur in BM of neutropenic LGLL patients, leading to a Fas-mediated apoptosis of myeloid or erythroid progenitors [48,49,50]. This evidence concerns the gene FAS and T-cell large granular lymphocyte leukemia.