Intragraft heat shock protein-60 expression after small bowel transplantation in the mouse

Intestinal Transplant Immunology and Intestinal Graft Rejection: From Basic Mechanisms to Potential Biomarkers

Intestinal transplantation (ITx) remains a lifesaving option for patients suffering from irreversible intestinal failure and complications from total parenteral nutrition. Since its inception, it became obvious that intestinal grafts are highly immunogenic, due to their high lymphoid load, the abundance in epithelial cells and constant exposure to external antigens and microbiota. This combination of factors and several redundant effector pathways makes ITx immunobiology unique. To this complex immunologic situation, which leads to the highest rate of rejection among solid organs (>40%), there is added the lack of reliable non-invasive biomarkers, which would allow for frequent, convenient and reliable rejection surveillance. Numerous assays, of which several were previously used in inflammatory bowel disease, have been tested after ITx, but none have shown sufficient sensibility and/or specificity to be used alone for diagnosing acute rejection. Herein, we review and integrate the mechanistic aspects of graft rejection with the current knowledge of ITx immunobiology and summarize the quest for a noninvasive biomarker of rejection.

What is the role of heat shock protein in abdominal organ transplantation?

Ischemia-reperfusion injury is a pathophysiological event occuring after abdominal organ transplantation, and has a significant influence on prognosis and survival of the graft. It is involved in delaying the primary function or non-functioning of the graft. The objective of this study was to provide information on heat shock protein mechanisms in ischemia-reperfusion injuries in abdominal organ transplantations, and to indicate the possible factors involved that may influence the graft outcome. Several classes of heat shock proteins are part of the ischemia and reperfusion process, both as inflammatory agonists and in protecting the process. Studies involving heat shock proteins enhance knowledge on ischemia-reperfusion injury mitigation processes and the mechanisms involved in the survival of abdominal grafts, and open space to support therapeutic future clinical studies, minimizing ischemia and reperfusion injuries in abdominal organ transplantations. Expression of heat shock proteins is associated with inflammatory manifestations and ischemia-reperfusion injuries in abdominal organ transplantations and may influence graft outcomes.

The Proteomic Signature of Intestinal Acute Rejection in the Mouse

Intestinal acute rejection (AR) lacks a reliable non-invasive biomarker and AR surveillance is conducted through frequent endoscopic biopsies. Although citrulline and calprotectin have been suggested as AR biomarkers, these have limited clinical value. Using a mouse model of intestinal transplantation (ITx), we performed a proteome-wide analysis and investigated rejection-related proteome changes that may eventually be used as biomarkers. ITx was performed in allogenic (Balb/C to C57Bl) and syngeneic (C57Bl) combinations. Graft samples were obtained three and six days after transplantation (n = 4/time point) and quantitative proteomic analysis with iTRAQ-labeling and mass spectrometry of whole tissue homogenates was performed. Histology showed moderate AR in all allografts post-transplantation at day six. Nine hundred and thirty-eight proteins with at least three unique peptides were identified in the intestinal grafts. Eighty-six proteins varying by >20% between time points and/or groups had an alteration pattern unique to the rejecting allografts: thirty-seven proteins and enzymes (including S100-A8 and IDO-1) were significantly upregulated whereas forty-nine (among other chromogranin, ornithine aminotransferase, and arginase) were downregulated. Numerous proteins showed altered expression during intestinal AR, several of which were previously identified to be involved in acute rejection, although our results also identified previously unreported proteome changes. The metabolites and downstream metabolic pathways of some of these proteins and enzymes may become potential biomarkers for intestinal AR.

Chronic Rejection After Intestinal Transplant: Where Are We in Order to Avert It?

Chronic rejection affects the long-term survival of all solid organ transplants and, among intestinal allografts, occurs in up to 10% of the recipients. The insidious clinical evolution of the chronic allograft enteropathy, the absence of noninvasive biomarkers, and the late endoscopic findings delay its diagnosis. No pharmacological approach has been proven effective, and allograft removal nowadays still represents the only available therapy. The inclusion of the liver in the visceral allograft appears to be the only intervention affecting the development of chronic rejection, as revealed by large-center studies and registry reports. A significant body of evidence emerged from the experimental setting and provided essential knowledge on the complex mechanisms behind the development of chronic allograft enteropathy. More recently, donor-specific antibodies have been suggested as an early, key element in the natural history of chronic allograft enteropathy and several novel approaches, tackling the antibody-mediated graft injury, have gained acceptance in clinical settings and are believed to impact on chronic rejection. The inclusion of a liver allograft is advocated when re-transplanting a sensitized recipient, due to its protective effect against humoral immunity. Multicenter trials are required to understand and tackle chronic rejection, and find the therapeutic answer to this clinical dilemma.

In vivo treatment of mice with heat shock protein, gp 96, improves survival of skin grafts with minor and major antigenic disparity

Immunization with high doses of heat shock protein, gp 6 given in vivo, has been shown to mediate the activation of CD4+ T cell, which in turn suppresses an ongoing CD8+ immune response. Here we demonstrate that high doses of gp 6 (HDgp 6) (100 microg given subcutaneously on days 0 and 7 following skin graft transplantation) improve survival of skin grafts with both minor and major histocompatibility. First, skin from male C57BL/6 donors was grafted onto female C57BL/6 recipients that were subsequently treated with either HDgp 6 or buffer and graft survival was monitored. At 64 days post-transplantation, graft recipients treated with HDgp 6 showed 56% graft survival compared to 10% in those treated with buffer. Further, HDgp 6 down regulates a secondary immune response as well. Skin graft obtained from a male C57BL/6 donor was transplanted to a female C57BL/6 recipient that had previously rejected a male skin graft. Recipients that were treated with HDgp 96 showed a 75% graft survival of the secondary graft at 64 days post-transplantation, whereas recipients treated with buffer rejected their secondary grafts within 37 days. Finally, the effect of HDgp 96 treatment on survival of graft with major histoincompatibility was tested. Skin grafts from female BALB/c donors were transplanted to female C57BL/6 recipients previously treated with either HDgp 96 or buffer. Although all the grafts were ultimately rejected, mice treated with HDgp96 showed a delay in the rejection as compared with buffer controls. Our findings indicate that HDgp 96 improves survival of grafts with both minor and major antigenic disparity and could lead to developing novel therapies in transplant medicine.