Sentinel Skin Allograft—A Reliable Marker for Monitoring of Composite Tissue Transplant Rejection

Previous studies have demonstrated that composite tissue transplants such as limbs reject more slowly than skin transplants. This has led to the hypothesis that a simultaneous skin graft may act as an effective marker of limb rejection. The aim of this study was to test the predictive value of a sentinel skin graft as a marker of rejection, using a hind limb transplantation model in rats. Lewis rat recipients received hind limb transplants alone from a Brown Norway donor (control; n = 15) or combined with a full-thickness 15 cm2 sentinel skin graft (n = 45). All animals received drug therapy (tacrolimus, mycophenolate mofetil, and prednisone) for 6 weeks; then, treatment was ceased entirely. Rejection of the skin graft and limb skin was assessed both by visual and histologic grading systems. Detectable visual rejection (grade 1) was observed earlier in the sentinel skin graft than in the limb skin (P < .0005); the clearest visual rejection (grade 2) appeared earlier in the sentinel skin graft (P < .005). The average histologic grade for early rejection of the skin graft was 1.46 and 1.08 for the limb skin (P < .05). These findings confirmed a visual and histologic delay in the rejection of limb skin compared with a distant sentinel skin graft. Skin grafts transplanted simultaneously with hind limbs may be a useful marker of early rejection.