Donor-specific human leukocyte antigen antibodies in intestinal transplantation. Curr Opin Organ Transplant. 2014;19:261-266. [PMID: 24811437 DOI: 10.1097/mot.0000000000000078]

Impacts of donor-specific anti-HLA antibodies and antibody-mediated rejection on outcomes after intestinal transplantation in children

AMR is a risk factor for graft failure after SBTx. We studied impact of DSAs and AMR in 22 children transplanted between 2008 and 2012 (11 isolated SBTx, 10 liver inclusive Tx, and one modified multivisceral Tx). Three patients never developed DSA, but DSAs were found in seven in the pre-Tx period and de novo post-Tx in 19 children. Pathology revealed cellular rejection (15/19), with vascular changes and C4d+. Patients were treated with IV immunoglobulins, plasmapheresis, and steroids. Rescue therapy included antithymocyte globulins, rituximab, eculizumab, and bortezomib. Pathology and graft function normalized in 13 patients, graft loss occurred in two, and death in seven. At the end of the follow-up, 15 children were alive (68%), 13 with functioning graft (59%). Prognosis factors for poor outcome after Tx were the presence of symptoms at AMR suspicion (P +.033). DSAs were often found following SBTx, mostly de novo. Resistant ACR or severe AMR is still difficult to differentiate, with a high need for immunosuppression in both. DSAs may precede development of severe disease and pathology features on the graft: relationship and correlation need to be better investigated with larger groups before and after Tx.

Successful Rescue of Late-onset Antibody-mediated Rejection 12 Years After Living-donor Intestinal Transplantation: A Case Report

BACKGROUND

Antibody-mediated rejection (ABMR) has recently surfaced as a potential form of graft dysfunction after intestinal transplantation.

METHODS

We present a case of an intestinal transplant recipient who developed late-onset ABMR 12 years after living-donor transplantation. An 18-year-old male recipient with a history of extensive intestinal resection secondary to acute bowel volvulus exhibited an excellent baseline immune profile for transplantation, including ABO-identical and HLA-haploidentical to the donor; a negative cross-match with a panel reactive antibody of 3.0%.

RESULTS

Post-transplantation immunosuppression consisted of tacrolimus, mycophenolate mofetil (MMF), and prednisone within the first year, followed by tacrolimus and MMF in the second year, and maintenance with tacrolimus monotherapy thereafter. The recipient experienced a single episode of indetermined acute cellular rejection 3 months after transplantation. Since then, he did not require any parenteral nutrition and had completely reintegrated with society. Twelve years later, the patient developed persistent diarrhea associated with transplant biopsy diffuse C4d deposition and circulating donor-specific antibodies. After the use of rituximab and intravenous immunoglobulin, the recipient stabilized 17 years after transplantation with complete recovery of intestinal mucosal damage.

CONCLUSION

Late-onset ABMR can emerge after transplantation and must be considered a possible cause of graft dysfunction in long-term intestinal transplantation survivors.

Intestine Transplantation Across a Positive Crossmatch With Preformed Donor-Specific Antibodies

BACKGROUND

We describe our experience using a modified protocol for immunosuppression for intestine transplantation across a positive crossmatch. Patients who underwent transplantation in 2013 were evaluated over a 12-month period for rejection and infectious events with comparison to procedure-matched controls on our standard protocol of immunosuppression.

PATIENTS AND METHODS

We used a modified protocol for intestine and multivisceral transplantation for patients with a positive flow crossmatch. In addition to our standard protocol, patients with positive crossmatch were given rituximab and intravenous immunoglobulin (IVIg) preoperatively. DSA was sent for clinical evaluation at monthly intervals. Patients were screened for rejection by endoscopic evaluation.

RESULTS

Four patients underwent transplantation within a single year across a positive crossmatch. Two received isolated intestine transplants and 2 had multivisceral transplantation (MVT). During the 12-month follow-up, 1 patients had an episode of severe acute cellular rejection, which was managed with increased immunosuppression. None of the patients had episodes of cytomegalovirus infection. One patient developed major infection and 3 patients developed minor bacterial infections. Among procedure-matched controls with negative final crossmatch on standard management (no preoperative rituximab or IVIg), 2 developed mild acute cellular rejection and 2 developed minor infections. One developed cytomegalovirus viremia with invasion to the colonic mucosa.

CONCLUSIONS

We report our protocol for immunosuppression for IT and MVT across a positive crossmatch. This allowed transplantation despite the presence of a positive crossmatch, with low rejection rates but potentially increased risk for major infections compared to the negative crossmatch controls on our standard protocol.

Intestinal Transplant Inflammation: the Third Inflammatory Bowel Disease

Intestinal transplantation is the most immunologically complex of all abdominal organ transplants. Understanding the role both humoral and innate and adaptive cellular immunity play in intestinal transplantation is critical to improving outcomes and increasing indications for patients suffering from intestinal failure. Recent findings highlighting the impact of donor-specific antibodies on intestinal allografts, the role of NOD2 as a key regulator of intestinal immunity, the protective effects of innate lymphoid cells, and the role of Th17 in acute cellular rejection are reviewed here.

Updates on antibody-mediated rejection in intestinal transplantation

Antibody-mediated rejection (ABMR) has increasingly emerged as an important cause of allograft loss after intestinal transplantation (ITx). Compelling evidence indicates that donor-specific antibodies can mediate and promote acute and chronic rejection after ITx. However, diagnostic criteria for ABMR after ITx have not been established yet and the mechanisms of antibody-mediated graft injury are not well-known. Effective approaches to prevent and treat ABMR are required to improve long-term outcomes of intestine recipients. Clearly, ABMR after ITx has become an important area for research and clinical investigation.

The Role of Natural Killer Cells in Humoral Rejection

Antibody-mediated rejection (AMR) has been identified among the most important factors limiting long-term outcome in cardiac and renal transplantation. Therapeutic management remains challenging and the development of effective treatment modalities is hampered by insufficient understanding of the underlying pathophysiology. However, recent findings indicate that in addition to AMR-triggered activation of the classical complement pathway, antibody-dependent cellular cytotoxicity by innate immune cell subsets also promotes vascular graft injury. This review summarizes the accumulating evidence for the contribution of natural killer cells, the key mediators of antibody-dependent cellular cytotoxicity, to human AMR in allotransplantation and xenotransplantation and illustrates the current mechanistic conceptions drawn from animal models.

Intestinal transplantation: The anesthesia perspective

Intestinal transplantation is a complex and challenging surgery. It is very effective for treating intestinal failure, especially for those patients who cannot tolerate parenteral nutrition nor have extensive abdominal disease. Chronic parental nutrition can induce intestinal failure associated liver disease (IFALD). According to United Network for Organ Sharing (UNOS) data, children with intestinal failure affected by liver disease secondary to parenteral nutrition have the highest mortality on a waiting list when compared with all candidates for solid organ transplantation. Intestinal transplant grafts can be isolated or combined with the liver/duodenum/pancreas. Organ Procurement and Transplantation Network (OPTN) has defined intestinal donor criteria. Living donor intestinal transplant (LDIT) has the advantages of optimal timing, short ischemia time and good human leukocyte antigen matching contributing to lower postoperative complications in the recipient. Thoracic epidurals provide excellent analgesia for the donors, as well as recipients. Recipient management can be challenging. Thrombosis and obstruction of venous access maybe common due to prolonged parenteral nutrition and/or hypercoaguability. Thromboelastography (TEG) is helpful for managing intraoperative product therapy or thrombosis. Large fluid shifts and electrolyte disturbances may occur due to massive blood loss, dehydration, third spacing etc. Intestinal grafts are susceptible to warm and cold ischemia and ischemia-reperfusion injury (IRI). Post-reperfusion syndrome is common. Cardiac or pulmonary clots can be monitored with transesophageal echocardiography (TEE) and treated with recombinant tissue plasminogen activator. Vasopressors maybe used to ensure stable hemodynamics. Post-intestinal transplant patients may need anesthesia for procedures such as biopsies for surveillance of rejection, bronchoscopy, endoscopy, postoperative hemorrhage, anastomotic leaks, thrombosis of grafts etc. Asepsis, drug interactions between anesthetic and immunosuppressive agents and venous access are some of the anesthetic considerations for this group.

Current understanding of alloimmunity of the intestinal graft

PURPOSE OF REVIEW

This review focuses on the known mechanisms of alloimmunity that occur after transplantation and what is being done in order to improve graft and patient survival, particularly in the long term.

RECENT FINDINGS

The presence of mismatched antigens and epitopes might relate directly to the development of de-novo donor-specific antibodies (DSA), and thus, rejection. In an abdominal wall transplant, the skin graft could be the first to show signs of rejection. The epithelial or endothelial cells are the main targets in acute and chronic rejection, respectively. Possible therapeutical targets are gut homing T cells and cells of the innate immune system. Chimerism development might mostly occur in isolated lymph nodes, but also in the epithelium, particularly after transplantation of bone marrow mesenchymal stromal cells.

SUMMARY

Ischemia-reperfusion, surgical injury, and bacterial translocation trigger the innate immune system, starting acute rejection. Interaction between donor and recipient immune cells generate injury and tolerance, which occur mostly in secondary lymphoid organs, lamina propria, and epithelium. Chronic rejection mostly affects the endothelial cells, generating graft dysfunction. DSA increase the risk of graft rejection both acutely and chronically, and the liver protects against their effects. Induction therapies deplete lymphocytes prior to implantation, and maintenance therapies inhibit T-cell expansion. Rejection rates are the lowest when depleting drugs and a combination of interleukin 2 receptor blockade, inhibition of T-cell expansion, and steroids are used as maintenance therapy. Chimerism and tolerogenic regiments that induce Tregs and prevent the development of DSA are important treatment goals for the future.