Comparison of Sensitivity of Immunocomplex Capture Fluorescence Analysis for Detecting Donor-specific Anti-HLA Class II Antibodies in Kidney Transplant Patients

Abstract

Background: Immunocomplex capture fluorescence analysis (ICFA) detects donor-specific antihuman leukocyte antigen (HLA) antibodies (DSA), but the detection sensitivity of HLA class II antibodies using conventional ICFA is as low as 57%. The aim of the study was to improve the detection sensitivity of HLA class II antibodies by ICFA, and compare the ICFA results with the Luminex single-antigen bead test.

Methods: Six DSA-negative kidney transplant donors and recipient pairs and 10 HLA class II DSA-positive pairs were included in the study. The detection sensitivity of modified ICFA was compared with conventional ICFA, and the ICFA results were compared with the Luminex single-antigen bead test.

Results: The index value of modified ICFA was higher than that of conventional ICFA. The cutoff value of conventional ICFA was 30,686 (MFI), which was improved to 19,405 using modified ICFA. Regarding the HLA-DQ antibody, 5 samples found to be positive by Luminex single-antigen bead testing were all negative using modified ICFA. The reason for this discrepancy could be related to: (1) the difference in detection sensitivity; (2) the difference in HLA antigen surface expression between naive lymphocytes and synthetic beads; or (3) the structure of synthetic HLA DQ antigen on the Luminex single-antigen beads.

Conclusion: The index value of the modified ICFA was higher than that of conventional ICFA, and the detection sensitivity of HLA class II antibodies was improved by modified ICFA. Further assessment is necessary to clarify the reasons for divergence between ICFA and Luminex single-antigen bead test results.