Posttransplant antibodies and fresh venous allograft failure in dogs.

Small diameter arterial reconstruction is usually achieved by use of the autologous long saphenous vein. As an alternative to this blood conduit, the venous allograft has been used with some success in the past, but is likely to be the target of an immune rejection reaction from the host. This study was designed to characterize humoral immune reactions possibly involved in the outcome of venous allografts. Ten mongrel dogs received a histoincompatible femoral vein allograft and an autograft as interposition grafts to both femoral arteries. They were investigated for donor-specific antibody development using donor splenocytes and cultured vascular endothelial cells (EC). Serum samples were collected at surgery, at 2 weeks, and every month until graft occlusion occurred. All autografts were patent at retrieval except one, and all allografts underwent thrombosis. In all dogs, donor-specific IgG development was observed that appeared specifically at 4 weeks and lasted until graft occlusion was detected. All reactive sera were cytotoxic to donor EC except one, and this reactivity was completely lost after serum absorption on donor splenocytes. This latter absorption resulted in the total loss of flow cytometric reactivity against donor EC in 3 dogs, whereas a low reactivity was still present in 4 dogs. Immunoblotting analysis showed a posttransplant reactivity against various protein bands on donor EC. Absorption of the reactive serum on donor splenocytes resulted in the loss of reactivity to proteins of approximately 40, 30, and 22 kDa in most experiments. Moreover, as demonstrated by immunofluorescence on cryostat sections of explanted grafts, IgG deposition was seen mainly in the media and the adventitia of the allografts but not in autografts. These results suggest that a donor-specific antibody response directed mainly against MHC antigens might play a role in the thrombosis of histoincompatible venous allografts, thus decreasing the patency rate.