TY  - JOUR
AU  - Doroshenko, Anastasia
AU  - Reimers, Matthias
AU  - Sawers, Gary
AU  - Schlaf, Gerald
PY  - 2026
DA  - 2026/09/22
TI  - Detection of Complement-Fixing Anti-HLA Antibodies by C3d-Detecting Luminex Technique. Is There Any Additional Diagnostic Value Not Available Through the Use of Standard Single Antigen Antibody Specification?
JO  - OBM Transplantation
SP  - 277
VL  - 10
IS  - 03
AB  - Donor-specific antibodies (DSA) directed against human leukocyte antigens (HLA) are regarded as the principal cause of graft failure, including allograft loss. Especially cytotoxic, i.e., complement-fixing, antibodies have long been classified as clinically highly deleterious in the context of graft failure. The complement-dependent cytotoxicity assay (CDC), performed in cell-tray analyses, has been used to define these antibodies for more than 40 years, but generally lacks sensitivity. Due to its limited resolution, which does not exceed the single-donor level, it also cannot specify distinct antigens, especially in highly immunized patients. About fifteen years ago, this problem was overcome by broadly established Luminex-based single-antigen specification assays (SAB), which identify antibodies directed against recombinant single HLA antigens. To specify complement-fixing antibodies of postulated higher clinical relevance, these assays were supplemented by two commercial kits, initially by the C1q assay and later by the C3d assay. Here, we used the C3d assay to investigate serum from 74 selected patients on kidney waiting lists, which represent three groups, each with increasing levels of immunization/panel-reactive antibodies (%PRA): (i) with only anti-HLA class I antibodies (n = 24); (ii) with only anti-HLA class II antibodies (n = 21); and (iii) with combined anti-HLA class I and class II antibodies (n = 29). Our data show that C3d assay-defined cytotoxicity, especially for anti-HLA class I antibodies, strongly correlates with the mean fluorescence intensity (MFI). Anti-HLA class I antibodies appear cytotoxic when corresponding SAB MFI values exceed 6,000 to 7,000, whereas below this threshold cytotoxicity does not appear. Dilution experiments showed that cytotoxic antibodies could be converted to non-cytotoxic antibodies simply by falling below this threshold MFI value. In contrast, anti-HLA class II antibodies with cytotoxicity-defining threshold MFI-values between 1,500 and 2,000 differ by having a higher proportion of non-cytotoxic antibodies that even lie above these MFI-values. Nevertheless, we conclude that due to strong correlations with SAB MFI-values (Pearson correlation coefficients of 0.69 for HLA-class I and 0.63 for HLA-class II), there is insufficient clinical applicability to justify the considerable amount of work involved, and especially the high associated costs, for routine use of the C3d assay.
SN  - 2577-5820
UR  - https://doi.org/10.21926/obm.transplant.2603277
DO  - 10.21926/obm.transplant.2603277
ID  - Doroshenko2026
ER  -