Abstract
Context and purpose: Organ exchange programmes are important in order to ensure organs to highly immunized kidney patients. In this case report, we describe a highly immunized patient in an acceptable mismatch program who had an unexpected positive Complement-Dependent Cytotoxicity (CDC) crossmatch with a deceased donor exchange.Main findings: Subsequent evaluation revealed donor specific antibodies characterized by serological epitopes, which included the HLA-DQα chain, were masked in the standard IgG Luminex assay unless the serum was diluted; however, the antibodies demonstrated high MFI values when the serum was pretreated with EDTA or analyzed with the C1q assay. These findings led us to evaluate the extent of masked anti-HLA-DQ antibodies that included HLADQα/ DQβ pairs rather than just the HLA-DQβ chains in 16 highly immunized patients on the kidney transplantation waiting list at our transplantation center. We determined that 25% of the patients had antibodies directed towards serological epitopes that involved the anti-HLA-DQα chain but were masked in the standard IgG assay.Principal conclusions: We conclude that masked anti-HLA-DQ antibodies directed towards serological epitopes that also involves the HLA-DQα chain are common and should be considered as they may cause a positive CDC crossmatch. Thus, donor specific HLA-DQ antibodies must be evaluated in relation to full HLA-DQα; DQβ pairs in the serological molecules of the donor.
Highlights
Donor specific human leukocyte antigen (HLA) alloantibodies (DSA) are risk factors for the development of rejection and decreased graft survival in kidney transplantation [1]
Main findings: Subsequent evaluation revealed donor specific antibodies characterized by serological epitopes, which included the HLA-DQα chain, were masked in the standard IgG Luminex assay unless the serum was diluted; the antibodies demonstrated high mean fluorescence intensity (MFI) values when the serum was pretreated with EDTA or analyzed with the C1q assay
Principal conclusions: We conclude that masked anti-HLA-DQ antibodies directed towards serological epitopes that involves the HLA-DQα chain are common and should be considered as they may cause a positive complementdependent cytotoxicity (CDC) crossmatch
Summary
Donor specific human leukocyte antigen (HLA) alloantibodies (DSA) are risk factors for the development of rejection and decreased graft survival in kidney transplantation [1]. A 51-year-old highly immunized (HI) man with terminal kidney failure secondary to hypertension was accepted in the Scandiatransplant acceptable mismatch program (STAMP) [2] for HI patients in September 2014 He received an organ offer in February 2015 with an unexpected positive B-cell crossmatch in a CDC-based assay as HLA-A;B;C, DRB1 and DQB1 mismatches were all among the predefined acceptable antigens based on the analyses performed using a Luminex SAB assay (One Lambda Inc., Canoga/Los Angeles, CA). Inhibition was defined as an MFI
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