FAS and graft versus host disease: In 2004, a clinical study conducted in humans by Socié et al., demonstrated that increased transplant-related mortality (TRM) was correlated with the expression in situ of apoptosis mediators such as TNF-α and Fas in the gastrointestinal (GI) tract during digestive GVHD, as well as increased cellular infiltration of neutrophils in target organs after allo-HSCT [51].