Role of anti-HLA antibodies in allograft rejection

Clinical Relevance of Pretransplant Testing for Anti-Human Leukocyte Antigen Antibodies in Iraqi Renal Transplant Patients

OBJECTIVES

The use of highly sensitive Luminex technology to assess the immunologic risk of renal transplant candidates have greatly added to the ability of stratifying patients and have paved the way to avoid hyperacute antibody-mediated rejection. Our aim was to understand how much the testing for pretransplant anti-HLA antibodies affects the decision for transplant and survival at 1 year posttransplant.

MATERIALS AND METHODS

From January 2014 to June 2017, 336 transplant candidates were tested by complement-dependent cytotoxicity and by the Luminex platform for anti-HLA antibodies in our nephrology and renal transplant center (The Medical City, Baghdad, Iraq). All clinical and laboratory data were noted. Our program is a living-donor, blood group-compatible donor program. All transplant patients (sensitized or not) were followed for 1 year, and the Kaplan-Meier method was used to determine survival rate.

RESULTS

Mean age of the study group was 34.07 ± 12.4 years. Of 336 transplant patients who were tested, there were 63 (18.75%) sensitized patients and 159 (47.35%) nonsensitized patients. Blood transfusion was the main cause of sensitization. Class I anti-HLA antibodies were detected in 54 of 63 sensitized patients (85.7%), and class II anti-HLA antibodies were detected in 39 of 63 sensitized patients (61.9%). Donor-specific antibodies were detected in 33/63 (52.3%). Thirteen sensitized patients (15.3%) underwent transplant. No incidences of hyperacute rejection were recorded. The 1-year survival of the nonsensitized patient group was 90%, whereas survival was 61.5% for the sensitized patient group.

CONCLUSIONS

Pretransplant testing for anti-HLA antibodies is undoubtedly useful for assessment of patient risk, to facilitate decisions regarding patient and donor selection, and to plan treatment strategies. The 1-year survival for sensitized patient was lower than for nonsensitized patients. More knowledge, experience, technology advancements, and support are needed to improve the Iraqi practice of transplanting sensitized patients.

De novo anti-HLA antibodies in renal allograft recipients: a cross-section study

BACKGROUND

The occurrence of anti-HLA antibodies plays a well established role in solid organ rejection. The development of x-MAP multiple bead technology (Luminex) has enabled more accurate detection and definition of these alloantibodies.

METHODS

In 267 kidney transplant patients with stable allograft function for ≥3 years, we analyzed the presence of anti-HLA antibodies by Luminex technology. These patients had no alloantibodies before transplantation, and the immunosuppression treatment was: tacrolimus, cyclosporine, mycophenolate mofetil, prednisone, everolimus, and/or sirolimus.

RESULTS

Fifteen of the 267 patients showed anti-HLA class I antibodies and 12 showed anti-HLA class II antibodies, Seven patients had donor-specific antibodies (DSA): 1 anti-HLA class I, 5 anti-HLA class II, and 1 with both classes. No differences were found between DSA and the use or not of any specific therapy. However, in the retrospective review, we found a higher incidence of acute rejection episodes in the immediate posttransplant period among patients who developed class II DSA than those without DSA.

CONCLUSIONS

The prevalence of patients with normal renal function who develop DSA beyond 3 years after transplantation was relatively low. Steroid or withdrawal replacement of calcineurin inhibitors with inhibitors of mammalian target of rapamycin seem to not be risk factors to increase the development of DSA. The finding that patients who developed DSA showed a higher rate of previous acute rejection episodes suggested that they should be monitored more frequently for HLA antibodies.

Clinical relevance of pretransplant human leukocyte antigen donor-specific antibodies in renal patients waiting for a transplant: a risk factor

The use of highly sensitive solid-phase antibody detection assays, including x-MAP multiple bead-based technology (Luminex), has greatly enhanced our ability to accurately detect and define very low levels of HLA antibodies. These developments have led to patients having increasing lists of antibody specificities (which may not be clinically relevant), resulting in a new "technological barrier" to transplantation in sensitized patients. Alloantibodies play a major role in all types of solid organ rejection; the presence of low-titer donor-specific antigen (DSA) identified pretransplant is associated with an increased risk of antibody-mediated rejection (AMR). However, these low-titer antibodies do not represent an absolute contraindication to transplant. Improvement in the diagnosis and treatment of AMR will allow sensitized patients with DSA to be successfully transplanted in the short term, but extended follow-up is required to ensure acceptable long-term graft survival in this group. These factors must be integrated into the decision algorithms for immunosuppressive treatment in patients at immunologic risk.