42-P IMMUNE-RELATED PATTERN IN PEDIATRIC RENAL (PR) PATIENTS IS ASSOCIATED WITH FALSE POSITIVES (FP)IN SOLID PHASE FLOW PANEL REACTIVE ANTIBODY ASSAY (SPA). Chee Loong Saw 1, David Blank 2, RoseDjiana 2, Allan Tulli 2, Cathy McIntyre 1, Barbara Iozzo 3, Lorraine Bell 3. 1 HLA Lab Division of Hematology,McGill University Health Centre, Montreal, QC, Canada; 2 Division of Biochemistry, McGill University HealthCentre, Montreal, QC, Canada; 3 Division of Nephrology, Montreal Children Hospital, Montreal, QC, Canada.

Aim: To evaluate the factors that cause FP in SpA in PR patients (pts)(Fig. 1) as we suspected them to beimmune-related.

Methods: Immunohematologic profiles of 3 pts with FP were compared with 2 pts without FP. The normalcontrols were selected based on normal negative SpA. All patients were non-sensitized at the time serum wasdrawn. Serum samples were evalueted by SpA and IgE assay. Relative eosinophils and other immunologicinformation was correlated. Attempt to absorb the immune factor using latex beads was made.

Results: Data is summarized in Table 1. After transplant, patient #1 began immunosuppression and thathas resulted in normal eosinophil count and IgE and SpA screen. Other patients are either not transplantedor are evaluated for zero PRA serum. PF in SpA is hypothetically immune-related. Since no clear parameterwas implicated, we evaluated the pattern and found that FP may be associated with high eosinophil countand high IgE. Nevertheless FP is not seen in SpA screen of adult patients with elevated IgE, a situation thattends to be associated with allergies (data not shown). A possibility is that IgE has nonspecific binding toSpA latex beads that could be partially treated with bead absorption (Fig. 1).[figure1][figure2]

Conclusions: The factors that cause FP in SpA are different in PR pts than adults and need further study.

78 Abstracts / Human Immunology 74 (2013) 51–173

43-P OUTCOME OF KIDNEY TRANSPLANTATIONS PERFORMED WITH PREFORMED ‘‘NATURAL’’ DONOR SPECIFICANTIBODIES. Caroline Suberbielle 1, Antoine Sicard 2, Lucile Amrouche 2, Maryvonnick Carmagnat 1, EricThervet 3, Michel Delahousse 4, Christophe Legendre 2, Dominique Charron 1, Renaud Snanoudj 2. 1 LaboratoireRegional d’Histocompatibilite ‘‘Jean Dausset’’, Hopital Saint Louis, Paris, France; 2 Service de Nephrologie,Hopital Necker, Paris, France; 3 Service de Nephrologie, Hopital Georges Pompidou, Paris, France; 4 Service deNephrologie, Hopital Foch, Suresnes, France.

Aim: Detection of preformed donor specific alloantibodies (DSA) with Luminex Single Antigen assay led tothe common observation that individuals without history of pregnancy, transfusion or transplantation couldhave ‘‘natural’’ anti-HLA antibodies (Ab).

Methods: We retrospectively analyzed the risk of antibody-mediated rejection (AMR) and graft outcome intwo groups of kidney transplant recipients with ‘‘natural’’ DSA present at time of transplantation: 21 patientsreceived a post-transplantation desensitization protocol and 20 patients a standard protocol. We comparedthem to a third group of 26 patients with preformed ‘‘non-natural’’ DSA within same range of MFI, treatedwith post-transplant desensitization. Sera from the day of transplantation were tested for class I and IIDSA by Luminex LABScreen� Single Antigen (One-Lambda Inc., CA, USA), beads showing a mean fluorescenceintensity (MFI) >500 were considered positive.

Results: Patients with natural Ab were similar regarding number of HLA mismatches, class of DSA and MFIof the immunodominant DSA (iDSA).The MFI of the natural iDSA ranged from 500 to 3267. In the ‘‘non-nat-ural’’ 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 oneyear in patients with natural DSA, the incidence of acute AMR was 10.0%, whatever the immunosuppressiveregimen, and was similar to that observed in patients with ‘‘non-natural’’ DSA (15.4%, p=0.47). In patientswith natural or non-natural DSA, glomerular filtration rate was similar and screening biopsies showed alow frequency of microvascular inflamation (g+ptc > 1 in 9.1 and 13.0% of cases, respectively), and no trans-plant glomerulopathy. Graft and patient survival were 100% whatever the group.

Conclusions: 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.

Abstracts / Human Immunology 74 (2013) 51–173 79