Dissection of effector pathways in the host-versus-graft response to bone marrow transplantation

We have dissected the role of the primary cytotoxic pathways Fas-FasL and perforin-granzyme in host-versus-graft reactions after allogeneic bone marrow transplantation. Sublethally irradiated female recipient mice deficient for FasL (B6.gld) or perforin (B6.prf-/-) were transplanted with bone marrow from B6 male donors. Donor engraftment in B6.prf-/- recipients was higher when compared with B6.gld, particularly when assessed by in vivo killing, demonstrating the importance of the perforin pathway over the Fas-FasL pathway. In the absence of both pathways, however, donor bone marrow engraftment was not fully restored identifying a role for an additional pathway(s) in the host-versus-graft response.