The use of TWEAK and Fn14 reagents to counter GVHD damage. (A) Currently, allogeneic transplant of hematopoietic stem cells (HSC) following whole body irradiation during treatment for leukemia or lymphoma blood cancer would elicit apoptotic GI cell damage through TWEAK stimulation of Fn14 receptors. (B) Use of an anti-Fn14 IgG blocking antibody (αFn14) prevents TWEAK-induced cellular damage, particularly in progenitor GI cells, which overexpress Fn14 receptor.