Detecting donor-specific antibodies: the importance of sorting the wheat from the chaff

Human leukocyte antigen(HLA)compatibility is very important for successful transplantation of solid organs.In this paper,we focused on the humoral arm of immunity in the clinical setting of organ transplantation:how HLA antibodies develop,how they can be detected,and what they can do to injure organ transplants.Specifically,we explore the technical perspectives of detecting donor-specific antibodies(DSA)in HLA laboratories,and use real-life clinical cases to explain the principles.Currently there are many tools in our HLA antibody detection toolbox:conventional cytotoxicity cross match,flow cross match,and solid phase assays using beads conjugated with single or multiple HLA antigens.Single antigen bead(SAB)assay is the most sensitive tool available for detecting HLA antibodies and assessing the immunological risk for organ transplant.However,there are intrinsic limitations to solid-phase assays and they are prone to both false negativity and importantly,false positivity.Denatured antigens on single antigen beads might be the most prominent source of false positive reactivity,and may have been underestimated by many HLA experts.No single assay is perfect and therefore multiple methods,including the less sensitive assays,should be employed to determine the clinical relevance of detected HLA antibodies.Thoughtful process,including knowledge of HLA systems,cross reactivity,epitopes,and the patient's clinical history should be employed to correctly interpret data.The clinical team should work closely with HLA laboratories to ensure accurate interpretation of information and optimal management of patients before and after organ transplantation.

The impact of alloantibodies directed against the second donor on long-term outcomes of repeat liver transplantation

Background:Despite reports that associate donor specific antibody(DSA)with rejection after liver transplantation,grafts are still allocated according to blood group(ABO)but not human leukocyte antigen(HLA)compatibility,possibly due to the absence of an easily discernible clinical association between adverse recipient outcome and DSA.Re-transplantation provides a test environment where the presence of preformed DSA is prevalent and its effect on outcome should be apparent.Methods:All patients undergoing a second liver transplantation with available pre-operative serum were included with the exception of ABO incompatible or multiple organ transplants.Banked sera were tested for anti-HLA antibodies with Luminex-based solid phase assays.Anti-HLA antibodies to the second donor(D2SA)were determined using antibodies specificity and HLA typing of 2nd liver donor.Results:Preformed HLA antibodies directed to second liver transplantation(D2SA)were found in 31(39%)of the 79 patients that were included in the study.Primary and re-transplantation characteristics were similar in both subgroups except first graft survival which was significantly shorter in recipients who are negative for D2SA.Mean survival of the second graft was similar in D2SA+and D2SA?cohorts[8.55(range,0.01–24.74)vs.7.56(range,0–23.53)years respectively,P=0.574].Mean patient survival after 2nd liver transplantation was similar in D2SA+and D2SA?cohorts[9.11(range,0.01–24.74)vs.8.10(range,0–23.53)years respectively,P=0.504].Subgroup univariate analysis demonstrated no detrimental effect of class,locus,or strength of D2SA on survival of the second liver transplant.In multivariate cox regression model,neither class I D2DSA(HR=1.101,P=0.92)nor class II D2SA(HR=1.74,P=0.359)were significant risks of graft failure.Conclusions:Presence of D2SA was not found to be associated with inferior outcomes in this retrospective cohort study of liver re-transplantation suggesting that changes to the allocation system are not required.