43-P

Abstract

Detection of preformed donor specific alloantibodies (DSA) with Luminex Single Antigen assay led to the common observation that individuals without history of pregnancy, transfusion or transplantation could have “natural” anti-HLA antibodies (Ab). We retrospectively analyzed the risk of antibody-mediated rejection (AMR) and graft outcome in two groups of kidney transplant recipients with “natural” DSA present at time of transplantation: 21 patients received a post-transplantation desensitization protocol and 20 patients a standard protocol. We compared them to a third group of 26 patients with preformed “non-natural” DSA within same range of MFI, treated with post-transplant desensitization. Sera from the day of transplantation were tested for class I and II DSA by Luminex LABScreen® Single Antigen (One-Lambda Inc., CA, USA), beads showing a mean fluorescence intensity (MFI) >500 were considered positive. Patients with natural Ab were similar regarding number of HLA mismatches, class of DSA and MFI of the immunodominant DSA (iDSA).The MFI of the natural iDSA ranged from 500 to 3267. In the “non-natural” group, the mean number of DSA per patient (1.9 ± 1.3 versus 1.4 ± 0.8 in the two natural groups, p =0.07), as well as theMFI of iDSA by selection, were similar in the patients with non-natural and natural DSA . At one year in patients with natural DSA, the incidence of acute AMR was 10.0%, whatever the immunosuppressive regimen, and was similar to that observed in patients with “non-natural” DSA (15.4%, p=0.47). In patients with natural or non-natural DSA, glomerular filtration rate was similar and screening biopsies showed a low frequency of microvascular inflamation (g+ptc > 1 in 9.1 and 13.0% of cases, respectively), and no transplant glomerulopathy. Graft and patient survival were 100% whatever the group. In conclusion, patients with natural DSA are able to mount AMR but with a favorable one-year outcome, similar to that observed in patients with “non-natural” DSA.