Monday, September 27, 2010 2:00 PM - American Society for ...

3-ORIgM ANTIBODIES SPECIFIC TO DONOR HLA-B61 ARE ASSOCIATED WITH REJECTIONOF A KIDNEY TRANSPLANT.Qingyong Xu 1,2 , Terry Akister 1 , Donna Rich-Sperling 1 , Elly Johnson 1 , Rajni Chibbar 2 , Ahmed Shoker 3 .1 Lab Medicine, St. Paul’s Hospital, Saskatoon, SK, Canada; 2 Pathology and Lab Medicine, University ofSaskatchewan, Saskatoon, SK, Canada; 3 Saskatchewan Transplant Program, St. Paul’s Hospital,Saskatoon, SK, Canada.Aim: To investigate causes of antibody-mediated rejection (AMR) in kidney transplant without any anti-HLA IgG antibodies.Methods: To detect IgM antibodies, sera were screened with LABScreen® beads with PE-conjugated antihuman IgM as 2 nd reagent. DTT-treated, IgM-inactivated sera were used as negative control.Results: A 45 years old male received a living unrelated kidney transplant. Patient’s pre-transplantation(Tx) PRA were negative with both ELISA and Flow methods. T-AHG XM and T/B FCXM were negative,while T/B extended long incubation CDC XM were positive. Auto antibodies were excluded with negativeauto XM by CDC and flow. Tx was proceeded based on the fact that there is no IgG antibody to donorHLA pre-Tx. Eighteen to 24 hours after Tx, urine volume dropped precipitously, serum creatinine rose bythree fold. A biopsy confirmed severe AMR. The patient was treated with thymoglobulin, MMF,immunoadsorption, IVIG, and achieved excellent graft function. We hypothesize that IgM anti-HLAantibodies cause positive extended CDC XM and are associated with AMR. T/B extended CDC XM arepositive with serum collected when patient was rejecting the transplant. T-AHG XM is negative and thereare no anti-HLA IgG antibodies by ELISA and Luminex methods. The positive T/B extended CDC XMbecome negative when serum IgM is heat-inactivated. This indicates that IgM antibodies may cause thepositive CDC XM. IgM anti HLA class I antibodies were found in the pre-Tx serum with LABScreenmixed antigen beads. With IgM SAB, antibodies to B7, B27, B60, B61, B73, and B81 are found in theserum pre-Tx and when the transplant was rejected. IgM donor specific antibodies to B61 is present pre-Tx(MFI=1564) and is elevated when the transplant is rejected (MFI=2439), but is very low when the kidneytransplant functions well (MFI=359) (MFI=359).Conclusions: Donor-specific anti-HLA IgM antibodies are able to cause AMR in kidney transplant.4-ORPOSITIVE VIRTUAL CROSSMATCH (VXM), NEGATIVE FLOW CROSSMATCH (FXM): ACASE OF ANTIBODY (Abs) TO DENATURED ANTIGEN (dAg).Manish J. Gandhi, Nancy A. Ploeger, Steven R. DeGoey. Mayo Clinic, Rochester, MN, USA.Aim: Donor specific antibodies(DSA) identified by solid phase assay(SpA) are used to screen donors byperforming VXM as a surrogate for XM. We present a case of positive VXM and negative FXM.Methods: 29 yr patient for combined heart/lung transplant (Tx) had positve VXM as SpA demonstratedDSA to HLA-B44 (MFI=13,486). Retrospective T & B-FXM were negative. Possible reasons andinvestigation for the same are: 1. HLA-Abs is allele specific Donor typing confirmed DSA. 2.Error inperforming FXM Repeat testing with historical sample & spleenic cells: negative 3.Error in performingSpA Unlikely as historical Abs profile similar to current result 4.Non-HLA Abs directed to beads/reagents.Unlikely as Abs profile similar using a different product from same manufacturer and a differentmanufacturer.Results: As the SpA have some proportion of dAg, Abs to the dAg was considered.SpA beads were acidtreated(AT) to denature antigens. AT beads with positive control demonstrated a significant decrease inMFI values:[figure1]AT and untreated beads with patient demonstrated similar Abs profiles:[figure2]Datademonstrate Abs specificity is to dAg.Conclusions: Clinical significance of positive VXM and negative FXM is unknown. Post-Tx patient wasstable and biopsies in the past 13 months are normal.