Evaluation of the highly sensitized transplant recipient

HLA sensitisation: can it be prevented?

Human leukocyte antigen (HLA) sensitisation occurs after transfusion of blood products and transplantation. It can also happen spontaneously through cross-sensitisation from infection and pro-inflammatory events. Patients who are highly sensitised face longer waiting times on organ allocation programmes, more graft rejection and therefore more side effects of immunosuppression, and poorer graft outcomes. In this review, we discuss these issues, along with the limitations of modern HLA detection methods, and potential ways of decreasing HLA antibody development. We do not discuss the removal of antibodies after they have developed.

Immunosuppression following heart transplantation: prospects and challenges

Immunosuppression after heart transplantation has significantly reduced the incidence of cellular rejection and improved patient outcomes with the routine use of calcineurin inhibitors. Antimetabolites and proliferation signal inhibitors add to the improvement in patient outcomes, particularly with respect to the reduced burden of cardiac allograft vasculopathy. Patients with antibody sensitization are potentially at higher risk of postoperative complications. Sensitized patients are undergoing heart transplantation with increased frequency, in part due to the emergence of ventricular assist device use as a bridge to heart transplantation. Despite improvements in immunosuppressive therapies, many challenges face physicians and patients, which will further refine and improve care of the post-heart transplant patient.

Identification of endothelial cell surface antigens encoded by genes other than HLA. A combined immunoprecipitation and proteomic approach for the identification of antigens recognized by antibodies against endothelial cells in transplant recipients

It has been known for some time that transplant recipients may have antibodies to endothelial cells which are not detected on lymphocytes. However, little progress has been made in the analysis of these endothelial antigens. In the present experiments we have attempted to characterize endothelial cell surface antigens to which antibodies were produced during graft rejection. We have used a panel of endothelial cells from umbilical cord veins and found that antibodies with a polymorphic pattern in the panel appeared to correlate with transplant failure of kidney allografts and with the development of transplant-related coronary artery disease (TCAD) in heart transplant recipients. Among 39 patients with kidney allografts, 21 were negative for antibodies to endothelial cells and did well and 18 were positive and had frequent transplant loss (p=0.001). In 18 patients with TCAD and 20 patients of a comparator group without TCAD, association of coronary disease with endothelial cell antibodies was observed (p<0.02). To characterize the endothelial antigens responsible for these serologic reactions we performed immunoprecipitation of reactive antibodies with the corresponding endothelial cell surface antigens, followed by protein identification of the target antigens. Nine proteins were identified in these experiments, 5 were non-polymorphic and appeared to represent autoantigens. Four of the isolated proteins appeared to be polymorphic. They were the Human Major Histocompatibility Complex class I chain-related gene A (MICA), already known to be associated with antibody production and graft failure, human keratin 1, a protein known to be polymorphic and expressed on the surface of endothelial cells, eukaryotic translation initiation factor (EIF) 2A and ErbB3-binding protein 1. The possible role of keratin 1 and the other antigens in allograft rejection requires further investigation.

Treatment update of sensitized pediatric kidney transplant recipients: a review

Sensitization of recipients is an increasing problem in children. Some case series in children exist comparing the diverse desensitizing protocols. These protocols include intravenous immunoglobulin, cytomegalovirus immune globulin, plasmapheresis, and some adjunctive therapies such as rituximab. Desensitizing protocols have advantages and disadvantages. Clinical trials are required to determine suitable protocols for sensitized pediatric recipients. We performed a systematic review of these protocols in children. A massive search was done in PubMed, Embase, and the Cochrane library system. The results of these studies are compared.

The use of the calculated panel-reactive antibody and virtual crossmatch in heart transplantation

PURPOSE OF REVIEW

Alloantibodies to human leukocyte antigens (HLAs) in patients awaiting heart transplantation are associated with prolonged wait time to transplant, increased risk of posttransplant rejection and cardiac allograft vasculopathy, and decreased survival. Solid-phase assays to determine antibody presence have allowed for the development of a calculated panel-reactive antibody to denote unacceptable antigens. The virtual crossmatch allows for the comparison of recipient HLA antibodies to prospective donor HLA antigens to safely match a patient to an appropriate donor without a prospective crossmatch.

RECENT FINDINGS

Expansion of the donor pool and decreased waiting time for heart transplant may be impacted by further assessment of the functional status of alloantibodies and novel means for desensitization. Sensitized patients who receive left ventricular assist device (LVAD) as a bridge to cardiac transplant appear to have similar postoperative 1-year outcomes compared with nonsensitized patients.

SUMMARY

Antibody sensitization poses an additional hurdle to patients awaiting heart transplantation. Functional antibody assessment, placement of a LVAD as bridge to cardiac transplant, and novel means of desensitization may impact a sensitized patient's ability to safely undergo heart transplantation.