P1756ANTI-ABO ANTIBODY- VERSUS ANTI-HLA ANTIBODY-INDUCED ANTIBODY MEDIATED REJECTION IN ABO-INCOMPATIBLE KIDNEY TRANSPLANT PATIENTS: RELATIVE INCIDENCE AND PHENOTYPE DIFFERENCE

Abstract

Abstract Background and Aims Antibody-mediated rejection(AMR) in ABO incompatible(ABOi) kidney transplant(KT) patients can either be due to donor-specific anti-HLA antibody(DSA) or anti-blood group antibody. The relative frequency and possible phenotype difference of these two types of AMR in ABOi KT patients have not been reported. Method Of 111 ABOi KT patients between 2007 and 2019 in our center, 15(13.5%) patients developed acute AMR diagnosed by indication biopsy. Since there is no histologic distinction between DSA- and anti-ABO-induced AMR, we assumed the causative antibody in each case based on anti-ABO level and DSA, measured in serum collected at the time of AMR. Results Of these 15 cases of acute AMR, 5 were attributable to anti-ABO(ABO-AMR) since anti-ABO titer was higher (≥16) and DSA was undetectable at the time of rejection. Five cases were attributable to DSA(DSA-AMR) since DSA was detectable and anti-ABO was lower during rejection. Another 3 cases with lower anti-ABO titer and undetectable DSA were also assumed to be DSA-induced, since this low level of anti-ABO is unlikely to cause rejection and DSA can be undetectable in DSA-induced AMR by adsorption of Ab on graft, as frequently seen in ABO-compatible patients Two cases with both higher anti-ABO titer and detectable DSA was regarded as undetermined. The onset of acute AMR was within 2 weeks in all cases(median 7.0 days) and comparable between DSA- and ABO-AMR. Initial anti-ABO titer was also not statistically different; median(range) 256(64-4096) in ABO-AMR and 64(16-256) in DSA-AMR. All the 5 patients with ABO-AMR had negative PRA before KT, whereas 5 of 8 patients with DSA-AMR had positive PRA before KT, and two DSA-AMR patients had preformed DSA before KT. There was no difference in peak creatinine and response to treatment. All the AMR were recovered by treatment and no graft was lost to rejection. No patient with ABO-AMR developed chronic AMR whereas one of DSA-AMR patients developed chronic AMR. Conclusion In summary, among 15 cases of acute AMR, 5 were ABO-AMR, 8 were DSA-AMR and 2 were undetermined. There was no difference in clinical feature between DSA- and ABO-AMR. No patient with ABO-AMR developed chronic AMR.