Background: Regulatory T-cells (Treg) are natural suppressors of autoimmunity. Previous studies indicate that immunosuppressive drugs, especially calcineurin-inhibitors, may interfere with Treg homeostasis. Inflammatory bowel disease (IBD) can relapse or develop de novo after liver transplantation. IBD is associated with a relative deficiency of Treg. The aim of this study was to determine the effect of long-term immunosuppression on the presence of Treg in the noninflamed colonic mucosa of liver transplant recipients.
Methods: Colonic biopsies of normal mucosa of 36 liver transplant recipients on different types of immunosuppression and 11 controls were studied. Treg marker Foxp3 and Treg products transforming growth factor-β (TGF-β) and interleukin-10 (IL-10) were studied by quantitative polymerase chain reaction (Q-PCR) and immunohistochemistry. TGF-β-induced Smad-protein 3 and 7 were studied by Q-PCR.
Results: No significant differences between controls and patients were observed in IL-10, TGF-β, and Smad expression. Mucosal Foxp3 mRNA levels and Foxp3+CD3+ cells were significantly reduced in transplant recipients using prednisone/azathioprine/tacrolimus compared with controls but no direct relationship between Foxp3 expression and 1 specific drug was detected.
Conclusions: These results challenge the hypothesis that calcineurin-induced reduction of Treg or TGF-β expression predisposes nontransplanted tissue to inflammation, but indicate that combined immunosuppression hampers Treg development in the intestine.
(Inflamm Bowel Dis 2007)