Case reportCase Report: Binding of a Clinically Relevant Human Leukocyte Antigen–DQα–Specific Antibody in a Kidney Graft Recipient is Inhibited by Donor-Type Human Leukocyte Antigen–DQβ Chain
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Case Description
A 34-year-old woman received her first renal allograft from a blood type–identical deceased donor in 2010. The patient type was HLA-A2,30(19); B18,44(12); DRB1*03; DQB1*02 and the donor type was HLA- A3,32(19); B44(12),57(17); DR07, 12; DQB1*03:01,03:03.
In pretransplantation serum of the patient, no HLA class I or class II antibodies were detected using complement-dependent cytotoxic (CDC) technique. Pretransplantation CDC crossmatch was negative against both T cells and B cells.
During
Methods
HLA antibodies in posttransplantation serum of the patient were detected with the Luminex single-antigen bead assay LABScreen. HLA-coated beads enabled identification of Immunoglobulin G (IgG) alloantibody specificities against HLA-A,-B,-C,-DRB1,-DQA1,-DQB1 antigens. The threshold for a positive response was set at a mean fluorescence intensity (MFI) of 1000.
High-resolution DQA1/DQB1 typing was done with single specific primer-polymerase chain reaction technique. The patient type was HLA-
Results
The Luminex assay on the 23-month posttransplantation serum of the patient revealed anti-DQ2 autoreactive antibodies (MFI 12,000–18,000) when using beads with the serological equivalent of HLA-DQβ. Considering both DQβ and DQα chains, the strongly reactive anti-DQ2 antibodies bound only to beads with recipient-type DQβ chains in combination with nonself DQα chains. The patient had no anti-DQ2 antibodies against the beads with self-type DQα/DQβ.
Examining DQβ chains and their serological
Discussion
Herein, we have demonstrated a surprising binding of an anti-HLA DQ antibody dependent on similarity to donor DQα chain and to recipient DQβ chain.
The Luminex analysis revealed anti-DQ7 and anti-DQ9 reactivity examining only the DQβ chains and their serological equivalents. The patient had antibodies against all beads coated with donor-identical DQα chains, so examining the DQβ as well as the DQα chains, the patient had broadly reactive DSAs. This indicates that the serological nomenclature is
Acknowledgments
We thank the staff at the Tissue Typing Laboratory for their technical assistance.
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