Intragraft Expression of Messenger RNA for Interleukin-6 and Tumor Necrosis Factor-α Is a Predictor of Rat Small Intestine Transplant Rejection

Detection of rejection after small intestine transplantation (SIT) is difficult, relying largely on histopathology. The purpose of this study was to determine if the intragraft expression of messenger RNA (mRNA) for interleukin-2 receptor (IL-2R), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF) correlated with rejection in a unidirectional, heterotopic rat SIT model. Graft samples were obtained on postoperative day (POD) 3, 5, 7, 8, 9, 10, 12, and 14. After staining, formalin-fixed samples were blindly evaluated for rejection. Reverse transcriptase polymerase chain reaction (rtPCR) using primers specific for β-actin, IL-2R, IL-6, and TNF was performed on liquid nitrogen-frozen samples. Semiquantitation was accomplished using radionuclide incorporation and beta-scintillation counting. Intestinal histopathology in all isografts (ISO) and POD 3 allografts (ALLO) was normal. Rejection progressed in ALLO from mild on POD 5 to severe by POD 8. rtPCR analysis revealed constitutive expression of IL-2R mRNA in both ISO and ALLO. TNF and IL-6 demonstrated significant increases in mRNA expression in ALLO compared to ISO beginning on POD 5. In summary, intragraft expression of IL-2R mRNA demonstrated late up-regulation in ALLO which did not correlate with rejection. TNF and IL-6 mRNA expression predicted rat SIT rejection. rtPCR analysis of TNF and IL-6 may serve as a useful diagnostic adjunct for rat SIT rejection.