False Positive Class II HLA Antibody Reaction Due to Antibodies Against Denatured HLA Might Differ Between Assays: One Lambda vs. Immucor

Dear Editor, The Luminex human leukocyte antigen (HLA) single-antigen bead assay (SABA) was developed as a sensitive and specific assay to detect HLA antibodies [1]. However, false positive reactions may occur in the SABA due to the effect of medications such as high-dose intravenous immunoglobulin, anti-thymocyte globulin, and anti-CD20 or the presence of antibodies against denatured HLA [1]. Several approaches to overcome this issue have been proposed, including the use of a pretreatment reagent that adsorbs non-specific antibodies or drugs and acid treatment to distinguish specific antibodies against denatured class I HLA [2]. The use of acid treatment and iBead (singleantigen flow bead) has largely resolved the problem caused by antibodies against denatured class I HLA [2, 3]. However, there is no method for distinguishing antibodies against denatured class II HLA. Antibodies against denatured class II HLA have been detected at a frequency of 11% in healthy male donors [4]. Pan-HLA-DR reactivity is a pattern typically observed in the presence of antibodies against denatured class II HLA [5]. Another study found allelic bead reactions with HLA-DRB1*09:01, DRB3*01:01, DRB3*02:02, DRB3*03:01, DPB1*02:01, DPB1*20:01, and DPB1*28:01 for antibody reaction against denatured class II HLA [6]. Here, we report a case of false positive reaction with an antibody against denatured class II HLA, which showed different reactivities in screening and while using identification beads and SABA kits from different manufacturers. This study was approved by the Institutional Review Board of Severance Hospital, Seoul, Korea (4-2019-0984). A 52-year-old female with end-stage renal disease caused by membranous nephropathy visited Severance hospital for her first kidney transplant in April 2016. She had no history of transfusion or desensitization, such as high-dose intravenous immunoglobulin, anti-thymocyte globulin, or anti-CD20, and her pregnancy history was unknown. The patient did not provide informed consent specific to this study but did provide consent for the test and signed a comprehensive agreement on the potential use of the donated sample for research purposes. Genomic DNA was extracted from the peripheral blood using the QuickGene-Mini80 DNA Isolation System (Fujifilm, Tokyo, Japan). HLA typing was performed without delay using Lifecodes HLA SSO Typing Kits (Immucor Transplant Technology, Stamford, CT, USA), which revealed HLA-A*11, *33; B*27, *54; DRB1*08, *14, DQB1*05, *08. The result of the initial