Intragraft localization of activated nuclear factor kappaB in recurrent hepatitis C virus disease following liver transplantation.

Nuclear factor kappaB (NF-kappaB) is activated during viral infection and is central to the regulation of host immune responses. The NF-kappaB activation status and its morphological sources were assessed by immunohistochemistry in allograft biopsy specimens of orthotopic liver transplantation patients with recurrent hepatitis C virus (HCV). Hepatocellular NF-kappaB immunostaining was detected in HCV cases compared with controls (nontransplant: P <.001; transplant: P =.006), which correlated with the number of NF-kappaB positive hepatocytes (P =.007) and contrasted to the absent to weak staining of controls (nontransplant: P =.001; transplant: P =.009). Enhanced NF-kappaB staining of cytokeratin 19-positive bile ducts and proliferating ductules in the HCV group was in contrast to controls. Intense NF-kappaB immunoreactivity was detected in CD68-positive Kupffer cells and macrophages of all HCV specimens compared with a few controls (nontransplant: P <.001; transplant: P =.001) and contrasted to the weak staining of controls (nontransplant: P <.001; transplant: P =.001). NF-kappaB-positive immunoreactivity correlated with the number of T cell receptor (TCR) alpha/beta-positive lymphocytes (P <.001), which was not observed in controls. In those HCV cases showing evidence of necroinflammatory activity (grade) and individual features of portal inflammation, periportal inflammation/piecemeal necrosis, lobular inflammation, and fibrosis (stage), higher NF-kappaB staining intensity scores within bile ducts, proliferating ductules, hepatocytes (piecemeal necrosis: P =.016; stage: P =.030), and lymphocytes (stage: P =.044) and increased number of NF-kappaB-positive cells within bile ducts, proliferating ductules (grade, lobular inflammation, piecemeal necrosis, stage: P =.022), hepatocytes, and lymphocytes were observed. Increased staining intensity and frequency of NF-kappaB-positive cells were similarly observed in HCV-positive allografts obtained from patients under tacrolimus- compared with cyclosporine-based immunosuppression. These data implicate an immunoregulatory role of intragraft NF-kappaB activation in the pathogenesis and progression of posttransplantation HCV disease recurrence.

CD40 expression on graft infiltrates and parenchymal CD154 (CD40L) induction in human chronic renal allograft rejection.

BACKGROUND: CD40-CD154 (CD40L) costimulatory signaling plays a pivotal role in the effector mechanisms of transplant graft rejection. In animal models, CD40-CD154 blockade induces long-term graft acceptance concurrent with an absence of chronic rejection (CR) lesions. Given the critical importance of CD40-CD154 interactions in the development of chronic transplant allograft rejection, the relevance of in situ CD40 and CD154 expression was assessed in human chronic renal allograft rejection. METHODS: The expression of CD40, CD154, CD68, and T-cell receptor (TCR)alpha/beta was analyzed by immunohistochemistry. Serial cryostat sections of snap-frozen core renal allograft biopsies were obtained from 30 renal transplant patients. Biopsy specimens received diagnoses of CR (N = 23) according to the Banff classification and were compared with controls (N = 7) consisting of stable allografts and normal kidney tissue. RESULTS: Striking CD40 staining of graft cellular infiltrates (P = 0.016) was observed in renal allografts with CR compared with controls. The CD40+ cellular infiltrates in CR were predominantly TCR alpha/beta + T cells and some CD68+ macrophages. These findings were contrasted by the low-level CD40 expression detected in glomeruli and tubules of CR and controls. However, glomerular induction of CD154 was observed in CR allografts (P = 0.028) as compared with controls. CD154 immunoreactivity was demonstrated on glomerular endothelial, epithelial, and mesangial cells. Moderate CD154 expression was detected on tubular epithelial cells, and only weak CD154 immunoreactivity was observed on the infiltrates in isolated CR cases. CONCLUSION: In human chronic renal allograft rejection, CD40 is expressed on graft-infiltrating cells of the T cell and macrophage compartments. CD154 expression is induced on glomerular and tubular epithelial cells during CR, demonstrating another novel source of CD154 expression. The data substantiate the potential contributory role of an interaction between CD40+ graft-destructive effector T cells and macrophages with CD154+ renal allograft parenchymal cells in the development of chronic renal allograft rejection.

CD40L (CD154) expression in human liver allografts during chronic ductopenic rejection.

The CD40-CD40L (CD154) interaction plays a pivotal role in the effector mechanisms of allograft rejection. Blockade of the CD40/CD40L costimulatory pathway prevents the development of chronic allograft rejection in several animal transplant models. The relevance of in situ CD40 and CD40L expression in human liver allografts was assessed by immunohistochemistry during ductopenic chronic rejection (CR). In CR allograft specimens (n = 8), marked CD40L expression was detected on Kupffer cells (KCs) and sinusoidal macrophages with a unique centrilobular distribution (P <.001). The CD40L+ KCs and macrophages were shown to be CD68+ after immunohistochemical analysis of serial sections with anti-CD68 monoclonal antibody. Moderate staining of vascular and sinusoidal endothelial cells and mononuclear infiltrates was observed in some CR cases. These findings were in contrast to the absence of CD40L expression in controls (n = 11) consisting of stable liver allograft and normal liver tissue specimens. Only occasional CD40 expression in some cases of CR and controls was observed. In CR, CD40L (CD154) expression is manifested on KCs and macrophages. The present novel data show another important cellular source of CD40L expression and suggest a potential role of KCs/macrophages and CD40/CD40L costimulatory interactions in the pathogenesis of chronic rejection ductopenic liver allograft.

Short-term T cell receptor directed immunotherapy induces organ specific peripheral tolerance in a strongly incompatible rat model.

We analysed the effect of selective alpha/beta-T cell elimination on allograft survival in a strongly histoincompatible DA-->LEWIS rat model by treatment of recipients with the mouse monoclonal antibody R73 two times before and seven times after transplantation. R73 induced virtually indefinite cardiac allograft survival in 44% of six-week-old LEWIS recipients, whereas donor-type skin allografts were rejected within 11 days. The remaining 56% of animals presented a mean cardiac survival time of 41 +/- 13 days. Graft prolongation was age dependent since in ten-week-old animals the survival time was only of 19 +/- 5 days (untreated controls: 7 +/- 1 days). R73 induced a rapid decrease of R73-positive T cells in the peripheral blood from 70% before treatment to 2%. From the fifth day of treatment a gradual T cell recovery was registered. The T cell marker CD5 decreased from 72% to 17% but recovered already from the second day of treatment. Determination of alpha/beta-TCR, CD3 and CD5 density on T cells during R73 therapy showed that the initial T cell decrease was due to T cell elimination, whereas modulation of alpha/beta-TCR was predominant during the following days. Anti-R73 antibodies appeared regularly during the first week of treatment and blocked R73 activity, indicating their anti-idiotypic nature. The present findings show that short-term R73 therapy is able to induce long-lasting allograft survival. This experimental model can be used to study the basis of peripheral organ specific T cell tolerance.