Graft versus host disease in a rat small bowel transplant model after T-cell depleted donor specific bone marrow infusion

Low cytoreductive regimen of irradiation associated to unmodified bone marrow infusion (UBM) does not prevent the occurrence of graft versus host disease (GVHD) after transplant. PURPOSE: In this study we evaluated the potential advantages of a long-term immunossupression and T-cell depleted bone marrow infusion (TCDBMI) in preventing the occurrence of GVHD after small bowel transplantation (SBTx). METHODS: Heterotopic SBTX was performed with Lewis rats as recipients and DA as donors and distributed into 5 groups according to the irradiation, duration of immunossupression and the use of UBM or TCDBMI: G1 (n=6), without irradiation and G2 (n=9), G3 (n=4), G4 (n=5) and G5 (n=6) was given 250 rd of irradiation. Groups 1,2,4 and G3 and 5 were infused with 100 x 10(6) UBM and TCDBM respectively. Animals in G1, 2, 3 were immunossupressed with 1mg/ FK506/Kg/IM for 5 days and G4 and G5 for 15 days. Anti CD3 monoclonal antibodies and immunomagnetic beads were used for T-cell depletion.Animals were examined for rejection, GVHD, chimerism characterization and ileal and skin biopsies. RESULTS: Minimal to mild rejection was observed in all groups; however, GVHD were present only in irradiated groups. Long-term immunossupression changed the severity of GVHD in G4 and G5. Rejection was the cause of death in G1 while GVHD in G2, 3, 4 and 5, not avoided by the use of TCDBMI. Total chimerism and T-cell chimerism was statistically higher in irradiated groups when compared to G1. CONCLUSION: Extended immunossupression associated to low dose of irradiation decrease the severity of GVHD, not avoided by the use of TCDBMI