Intragraft and Systemic Immune Parameters Discriminating Between Rejection and Long-Term Graft Function in a Preclinical Model of Intestinal Transplantation.

BACKGROUND: The pathology and diagnosis of acute and chronic rejection in intestinal transplantation (ITX) are far from being completely understood. We established models of acute and chronic intestinal graft rejection and analyzed peripheral and intragraft immune responses. METHODS: We performed ITX from Dark Agouti into Lewis rats applying single-dose tacrolimus (TAC) at varying concentrations. Graft histology and immunohistology were assessed on postoperative day (POD)7, 14, and 45. Intragraft and peripheral gene expressions of inflammatory and anti-inflammatory markers and lipopolysaccharide binding protein (LBP) plasma as well as alloantibodies were measured simultaneously. RESULTS: A 1-mg TAC resulted in acute rejection and recipient death; 3 mg and 5 mg prolonged survival and led to severe or moderate chronic rejection, respectively, with 50% of the 5-mg TAC recipients surviving the observation period. Consequently, we observed severe infiltration on POD7 in untreated and 1-mg TAC recipients compared with minor histological alterations in 3 and 5 mg TAC groups. Only 5-mg TAC treatment prevented accumulation of CD4+ T cells and ED1+ macrophages over the entire observation period. Peripheral and intragraft expressions of T cell activation inhibitor-mitochondrial were stable in long-term surviving 5-mg TAC recipients but declined before acute or chronic rejection in 1 and 3 mg TAC recipients. In contrast, LBP levels increased during acute and chronic rejections. CONCLUSIONS: We studied acute and chronic rejections in a preclinical model of ITX, which recapitulates clinical findings and highlights the importance of monitoring peripheral T cell activation inhibitor-mitochondrial expression, LBP levels, and antidonor antibodies for revealing rejection.

Non-HLA Antibodies May Accelerate Immune Responses After Intestinal and Multivisceral Transplantation.

BACKGROUND: Non-HLA alloantibodies and autoantibodies are involved in allograft rejection in kidney and heart transplantation. Their role in intestinal transplantation has not yet been described. We examined the development of antiangiotensin II type I receptor antibodies (anti-AT1R) and antiendothelin type A receptor antibodies associated with the clinical course and histopathological findings of intestinal transplantation recipients. METHODS: Thirty-seven patients underwent intestinal or multivisceral transplantation. Non-HLA antibodies (non-HLAabs) were screened in 29 transplant recipients. Antibody-levels greater than 12 U/L were considered positive and were evaluated retrospectively regarding rejection episodes. RESULTS: Twenty patients developed anti-AT1R and/or antiendothelin type A receptor antibodies (non-HLAabs group), 9 did not (control group). The non-HLAabs group had a higher rate of allograft rejection than controls (80% vs 55%), especially a higher rate of antibody-mediated rejections (55% vs 11%, P < 0.01) with detection of donor-specific anti-HLAabs. All rejection episodes in the non-HLAabs group appeared around the time of positive non-HLAabs detection. Five patients had acute cellular rejections at the time of non-HLAabs development, 4 had viral infections. CONCLUSIONS: Our data suggest that antibody-mediated mechanisms targeting antigens beyond HLA may trigger and accelerate immune responses. Given the possibility of pharmacologic targeting of non-HLA receptors, future studies will focus on the explanation of mechanisms how non-HLAabs may enhance rejection and affect long-term allograft survival.