Xiaohai Zhang

Optimizing transplantation of sensitized heart candidates using 4 antibody detection assays to prioritize the assignment of unacceptable antigens.

BACKGROUND The virtual crossmatch relies on the assignment of unacceptable antigens (UAs) to identify compatible donors. The purpose of our study was to identify an algorithm for assignment of UAs such that a negative complement-dependent cytotoxicity (CDC) crossmatch and concomitant negative or weakly positive flow cytometric crossmatch (FXM) are obtained. METHODS We used 4 antibody methods: (1) Luminex single antigen (LSA), (2) LSA with a 1:8 serum dilution, (3) C1q LSA, and (4) CDC panel. The UAs were prioritized in the following order: (1) all C1q+/CDC+, (2) LSA 1:8 >7,500 median fluorescence intensity, and (3) LSA >10,000 median fluorescence intensity. RESULTS Of 295 heart transplants that were performed at our center, 69 (23%) recipients had detectable human leukocyte antigen specific antibody at the time of transplant. All donor specific antibodies (DSAs) were avoided for 44 of 69 (64%) (DSA-). There were 25 recipients who had DSA at the time of transplant: 12 (48%) had negative FXM (DSA+/FXM-), and 13 (52%) had positive T-cell and/or B-cell FXM (DSA+/FXM+). Lower freedom from antibody-mediated rejection was observed for the DSA+/FXM+ group compared with the DSA- group (p < 0.0001). DSA remained detectable after transplant in the sera of 14 recipients, and de novo DSA was detected in 32 recipients. Freedom from antibody-mediated rejection was comparable for both groups (p = 0.53) but was lower than the DSA- group (p < 0.0001). Survival was comparable for all groups at 1,200 days post-transplant. CONCLUSIONS Strategic prioritization of UA assignment has allowed transplantation of highly sensitized patients across the DSA barrier with survival rates comparable to DSA- heart transplant recipients.

A 3-Center study reveals new insights into the impact of Non-HLA antibodies on lung transplantation outcome

Background The presence of antibodies to angiotensin type 1 receptor (AT1R) and endothelin type A receptor (ETAR) is associated with allograft rejection in kidney and heart transplantation. The aim of our study was to determine the impact of AT1R and ETAR antibodies on graft outcome in lung transplantation. Methods Pretransplant and posttransplant sera from 162 lung recipients transplanted at 3 centers between 2011 and 2013 were tested for antibodies to AT1R and ETAR by the enzyme-linked immunosorbent assay (ELISA) assay. Clinical parameters analyzed were: HLA antibodies at transplant, de novo donor-specific antibodies (DSA), antibody-mediated rejection (AMR), acute cellular rejection, and graft status. Results Late AMR (median posttransplant day 323) was diagnosed in 5 of 36 recipients with de novo DSA. Freedom from AMR significantly decreased for those recipients with strong/intermediate binding antibodies to AT1R (P = 0.014) and ETAR (P = 0.005). Trends for lower freedom from acute cellular rejection were observed for recipients with pretransplant antibodies to AT1R (P = 0.19) and ETAR (P = 0.32), but did not reach statistical significance. Lower freedom from the development of de novo DSA was observed for recipients with antibodies detected pretransplant to AT1R (P = 0.054), ETAR (P = 0.012), and HLA-specific antibodies (P = 0.063). When the pretransplant antibody status of HLA-specific antibody (hazard ratio [HR], 1.69) was considered together with either strong binding to AT1R or ETAR, an increased negative impact on the freedom from the development of de novo DSA was observed (HR, 2.26 for HLA antibodies and ETAR; HR, 2.38 for HLA antibodies and ETAR). Conclusions These results illustrate the increased negative impact when antibodies to both HLA and non-HLA antigens are present pretransplant.

Comprehensive assessment for serum treatment for single antigen test for detection of HLA antibodies

The single antigen test is widely used in the field of transplantation to determine the specificity of HLA antibodies. It will be beneficial to standardize the procedure of the single antigen test among HLA laboratories. It is not uncommon that single antigen testing on native sera fails to detect antibodies with very high concentrations. It has been shown that cleavage products of activated complement components may mask strongly binding antibodies in single antigen testing. To overcome inhibition by the activated complement products, sera are pretreated with ethylenediaminetetraacetic acid (EDTA), dithiothreitol (DTT), or heat inactivation before single antigen testing. However, no studies have been published to systemically compare the impact of these treatments on single antigen testing. The aim of this study is to understand the different effects these treatments may have on single antigen test results. We found that mean fluorescence intensity (MFI) obtained from sera treated with EDTA and heat inactivation were nearly identical, while DTT treatment was less potent to remove the inhibition. In addition, sera dilution did not further increase MFI of antibodies after EDTA treatment. Our results provide guidance to choose a pretreatment reagent for single antigen testing, and to compare studies obtained from laboratories using different treatments.

Non-human leukocyte antigen-specific antibodies in thoracic transplantation.

Purpose of reviewDevelopment of donor human leukocyte antigen (HLA)-specific antibodies is associated with graft loss, yet the role of non-HLA antibodies in solid organ transplant needs to be further defined. It is suggested that HLA antibodies and non-HLA antibodies collaborate together to impact graft outcome. This review focuses on the latest findings on antibodies against these non-HLA antigens in thoracic organ transplant. Recent findingsThese non-HLA antigens include signaling proteins expressed on the cell surface, such as angiotensin II type 1 receptor (AT1R), endothelin type A receptor, and structure proteins, such as myosin, vimentin, and K&agr;1 tubulin, and extracellular matrix protein collagen. Antibodies against these antigens may impact the allograft in different ways. Although these non-HLA antibodies can damage the allograft through complement-mediated or cell-mediated cytotoxicity, antibodies against AT1R and endothelin type A receptor can also alter the endothelial cell function by activating intracellular signals. The presence of these non-HLA antibodies may predispose the patient to develop HLA-specific antibodies. Recently, it has been shown patients with AT1R antibodies pretransplant have a higher chance to develop de-novo donor-specific HLA antibodies. SummaryThe findings suggest it is important to stratify the patients immunologic risk by assessing both the HLA and non-HLA-specific antibodies.

Revealing a new mode of sensitization induced by mechanical circulatory support devices: Impact of anti-AT1R antibodies

Increased levels of angiotensin II type 1 receptor (AT1R) antibody have been shown to be associated with allograft rejection. This study aims to determine the rate of development of antibody to AT1R after mechanical circulatory support device (MCS) implantation, and if the development of strong binding AT1R antibodies is associated with survival.

Impact of Non-Human Leukocyte Antigen-Specific Antibodies in Kidney and Heart Transplantation

The presence of donor human leukocyte antigen (HLA)-specific antibodies has been shown to be associated with graft loss and decreased patient survival, but it is not uncommon that donor-specific HLA antibodies are absent in patients with biopsy-proven antibody-mediated rejection. In this review, we focus on the latest findings on antibodies against non-HLA antigens in kidney and heart transplantation. These non-HLA antigens include myosin, vimentin, Kα1 tubulin, collagen, and angiotensin II type 1 receptor. It is suggested that the detrimental effects of HLA antibodies and non-HLA antibodies synergize together to impact graft outcome. Injury of graft by HLA antibodies can cause the exposure of neo-antigens which in turn stimulate the production of antibodies against non-HLA antigens. On the other hand, the presence of non-HLA antibodies may increase the risk for a patient to develop HLA-specific antibodies. These findings indicate it is imperative to stratify the patient’s immunologic risk by assessing both HLA and non-HLA antibodies.

Overview of Transplantation Immunobiology

The immune system protects us from infection by recognizing pathogens, and destroying or containing them. The immune system can be categorized into two branches: the innate immune system and adaptive immune system. The innate immune system and adaptive immune system are not completely independent systems. Instead, there is crosstalk at multiple levels and collaboration with each other to mount immune response to pathogens. The processes that initiate transplant-directed alloimmune responses are mediated by components unrelated to organ transplantation but rather are developed from a system that maintains the integrity against various pathogens. Exposure to pathogens such as viruses, bacteria, fungi and protozoa first countered by the innate immune system composed of inflammatory cells, usually granulocytes, which include neutrophils, eosinophils, basophils, and mast cells. A second important cellular component of the innate immune response includes the monocytes, macrophages, and dendritic cells, which can take up and process exogenous materials. Also included in the cellular innate immune response are the γδ and natural killer (NK) cells, which can kill virally infected cells without prior sensitization [1]. These same cells survey the periphery including transplanted organs with usually a slower response than that observed in innate immune responses against pathogens.