ABSTRACT
T lymphocytes and NK cells play an important role in the graft-versus-host (GVH) disease. IL-12 is known to activate both lymphocyte subpopulations. Here, we examined the effect of IL-12 on the outcome after allogenic bone marrow transplantation (allo-BMT). Experiments were performed in a major histocompatibility complex (MHC)-matched allo-BMT model from DBA/2 to BALB/c mice. We administered IL-12 subcutaneously to recipient BALB/c mice at the day of BMT and 2 days later. At a dose of 200 ng IL-12, mice died between day 4 and day 10. When 50 ng of IL-12 was administered, 50% of the animals died, at a dose of 25 ng all mice recovered. In vivo blocking experiments with antagonistic monoclonal antibodies indicated that the early lethality was mediated by FasL, IFNgamma and TNFalpha. Recognition of third party antigens by donor, but not recipient lymphocytes caused lethality. HE staining of the large intestine of IL-12 treated animals showed a severe mucosal injury associated with infiltrating lymphocytes and apoptotic bodies. In IL-12 treated mice in contrast to untreated control animals, flow cytometry analysis revealed numerous CD3+ T cells and CD11c+ dendritic cells (DC) were found in the large intestine. The interaction of T cells and antigen presenting DC might contribute to the lethality in our system. In light of these findings, the usefulness of IL-12 application for patients after BMT is rather questionable.
