Modification of rejection by polyethylene glycol in small bowel transplantation

The use of polyethylene glycol (PEG) in preservation solutions has been associated with a decreased incidence of rejection in clinical and experimental organ transplantation. In this study, we examined the effect of PEG with different molecular configurations on rejection of small bowel allografts in the rat. Male ACI and LEW rats were used as donors and recipients, respectively. Orthotopic small bowel transplantation was performed using the following preservation solutions: lactated Ringer's solution (n = 7), University of Wisconsin solution (n = 7), University of Wisconsin solution without hydroxyethyl starch (sUW; n = 7), sUW with PEG20M (n = 9), sUW with PEG8000 (n = 6), and sUW with PEG20L (n = 7). No immunosuppression was given. In orthotopic small bowel transplantation, only groups with a high molecular weight PEG, PEG20M and PEG20L, demonstrated longer survival (P < 0.01 and P < 0.001, respectively) and delayed onset of unkempt appearance (P < 0.05 and P < 0.001, respectively). In heterotopic small bowel transplantation, sUW was compared with sUW with PEG20L. Rejection occurred later and its progression was slower in the sUW with PEG20L than in the sUW alone. Our observations suggest that the onset and progression of rejection after small bowel transplantation were influenced by the molecular weight and configuration of the PEG molecule. The mechanism is unclear, but high molecular weight PEG appears to reduce or change the immunogenicity of the small bowel allograft.