Background
Skin rejection episodes with the need of lifelong immunosuppression limit the widespread introduction of Vascularized composite allotransplantation (VCA). Cytokine expression profiles revealed that IL-1b was highly upregulated in biopsies of rejecting skin. We investigate the effect of an IL-1b-blocker on skin rejection in a rat VCA model.
Methods
Anti-IL-1b was applied in an experimental rat hindlimb transplantation model (Brown Norway (BN) rats to Lewis (LEW) rats). Four different treatment groups included: No treatment (1); baselineimmunosuppression consisting of FK506 30 mg/kg 50 days, ALS 0.5 mL day 0 + 3 (2), baseline immunosuppression + weekly injections of Anti-IL1b subcutaneously (s.c.) into the transplanted limb (3), baselineimmunosuppression + Anti-IL1b s.c. into the contralateral, non-transplanted limb (4). End-point was rejection grade III or postoperative day 100. Graft infiltrating cells were isolated and assessed for T cell populations using flow cytometry. Skin transplantations of BN and 3rd party rats were performed in long-survivors (> 100 days) to assess for tolerance.
Results
Weekly s.c. injections of Anti-IL-1b into the transplanted limb (group 3) resulted in significant prolongation of allograft survival (mean survival 81,3 days) as compared to the control group (2) (64 days); P = < 0,05. Two limbs of the group 3 animals only showed mild signs of rejection on day 100. Weekly injections of IL-1b into the non-transplanted, contralateral hindlimb (4) also significantly prolonged allograft survival (mean survival 97,2 days) compared to group 2. 4/5 animals reached day 100 with no or only mild signs of rejection. Animals without any treatment (1) rejected on day 7,5 ± 0,5. No differences in graft infiltrating CD45+CD3+CD4 T cells, CD45+CD3+CD8+ T cells and CD3+CD4+CD25+Foxp3+ T regs were observed between groups. BN and 3rd party skin grafts transplanted in long survivors after day 100 were rejected. Gene expression of the cytokines IL-1a, IL-1b, IL-6 and TNF-a was significantly decreased in the skin of local treated animals (3) compared to untreated controls (1), but not to the other control groups (2 + 4).
Conclusions
IL-1b is a promising target for immunosuppression in extremity transplantation. Blocking IL-1b prolongs limb graft survival when given into the allograft or the contralateral limb in a rat VCA model.