Establishment of a Hyperacute Rejection Model of ABO-Incompatible Renal Transplantation in Nonhuman Primates

The establishment of a hyperacute rejection (HAR) model of ABO-incompatible kidney transplantation (ABOi-KTx) in nonhuman primates is of great significance for the study of the relevant clinical pathophysiological processes and related interventions in ABOi-KTx. In this study, blood group B cynomolgus monkeys were presensitized with synthetic blood group A-antigen conjugated to keyhole limpet hemocyanin (A-KLH) to boost circulating anti-A antibody levels. The serum anti-A antibody levels were measured by flow cytometry using type A human reagent red blood cells (RBCs) or monkey primary renal tubular epithelial cells (RTECs) as target cells. ABOi-KTx was performed in type B monkeys using type A monkeys as donors. After 14 days of A-KLH sensitization, 12 of 16 (75%) type B monkeys had significantly elevated anti-A antibody levels. We found that in order to avoid irregular results in the detection of blood group antibodies by flow cytometry, it was more effective to use RTECs rather than RBCs as target cells. In the absence of presensitization, ABOi-KTx in three monkeys with relatively high levels of natural anti-A antibodies did not produce HAR. However, when four Type B monkeys with significantly increased anti-A antibodies after presensitization were randomly selected as recipients for ABOi-KTx, the allografts in all four monkeys developed HAR with typical pathologic characteristics. Thus, we have successfully established a monkey model of HAR in ABOi-KTx via blood group antigen presensitization, which will be helpful for the further study of rejection, accommodation, and clinical intervention in ABOi-KTx.

The Great Ormond Street Hospital immunoadsorption method for ABO-incompatible heart transplantation: a practical technique

Traditionally, ABO-incompatible heart transplantation was accomplished using a plasma exchange technique to remove recipient plasma containing donor-incompatible anti-A/B isohaemagglutinins. However, this technique exposed patients to large volumes of allogeneic blood and blood products (up to three times the patient’s circulating volume). In 2018, we published the first reported case of an ABO-incompatible heart transplant using an intraoperative immunoadsorption technique which minimises the exposure to blood products by specifically targeting anti-A/B isohaemagglutinins. We have subsequently used this technique in all children undergoing ABO-incompatible heart transplantation and become convinced of its efficacy in this population while observing no adverse effects. This article outlines the practical details required to perform the technique in order to avoid hyperacute rejection.

P1797ACUTE RENAL GRAFT FAILURE ASSOCIATED WITH AT1 RECEPTOR ANTIBODIES : 2 CASES IN SKMC

Background and Aims Some kidney transplantation recipients with negative donor specific antibodies can develop acute rejection episodes which are difficult to treat, associated with non-HLA antibodies like angiotensin 2 type 1 receptor antibodies (AT1R Ab). The mechanism of rejection by AT1R ab involves vascular injury. Our cases are unique as the first patient got mineralocorticoid deficiency like picture unexpectedly. For the second case, hyperacute rejection cause in the first allograft was not identified and but hyperacute rejection episodes involving antibodies against endothelial cells are reported in literature. Method 2 patients received renal transplantation from life related donors in out institute developed acute rejection episodes. As part of investigations, we did non -HLA antibodies testing which came positive . Results Case 1 30 years old male, with end stage renal disease on hemodialysis . The patient had a live related renal transplant with Mismatch 1-1-1 and negative DSA. Induction with Basiliximab was initiated but changed to ATG due to delayed graft function. Kidney biopsy on day 6 post operatively showed diffuse moderate to severe acute tubular injury (up to necrosis) with glomerular intracapillary fibrin microthrombi, focal minimal peritubular capillaritis and mild glomerulitis and focal weak C4d positivity, highly suspicious for active antibody mediated rejection. The patient was treated with pulse steroids, ATG total of 7.5mg/kg, 3 sessions of Plasma exchange and IVIG 2 g/kg and 2 doses of Rituximab for his hyperacute rejection. AT1R antibodies titer was 11U/ml. MICA was negative. Losartan was initiated as a maintenance therapy.

Targeting αGal epitopes for multi-species embryo immunosurgery

Immunosurgical isolation of the inner cell mass (ICM) from blastocysts is based on complement-mediated lysis of antibody-coated trophectoderm (TE) cells. Conventionally, anti-species antisera, containing antibodies against multiple undefined TE-cell epitopes, have been used as the antibody source. We previously generated α-1,3-galactosyltransferase deficient (GTKO) pigs to prevent hyperacute rejection of pig-to-primate xenotransplants. Since GTKO pigs lack galactosyl-α-1,3-galactose (αGal) but are exposed to this antigen (e.g. αGal on gut bacteria), they produce anti-αGal antibodies. In this study, we examined whether serum from GTKO pigs could be used as a novel antibody source for multi-species embryo immunosurgery. Mouse, rabbit, pig and cattle blastocysts were used for the experiment. Expression of αGal epitopes on the surface of TE cells was detected in blastocysts of all species tested. GTKO pig serum contained sufficient anti-αGal antibodies to induce complement-mediated lysis of TE cells in blastocysts from all species investigated. Intact ICMs could be successfully recovered and the majority showed the desired level of purity. Our study demonstrates that GTKO pig serum is a reliable and effective source of antibodies targeting the αGal epitopes of TE cells for multi-species embryo immunosurgery.