Circulating anti‐glomerular basement membrane autoantibodies against α3(IV)NC1 undetectable by commercially available enzyme‐linked immunosorbent assays

Abstract

Circulating anti-GBM antibodies undetectable by ELISA could recognize cryptic and conformation-dependent epitopes restricted on α3(IV)NC1, distinct from E(A) and E(B) . Indirect immunofluorescence was necessary for antibody detection and treatment monitoring under such circumstances.

Circulating Anti–Glomerular Basement Membrane Antibodies With Predominance of Subclass IgG4 and False-Negative Immunoassay Test Results in Anti–Glomerular Basement Membrane Disease

“…Another possible explanation for false negative results is autoantibodies reacting with a different antigen or epitopes as compared with "regular" anti-GBM antibodies, that all react with two well defined epitope regions of the NC1-domain of Type IV collagen α3-chains 12 . Such findings were recently described in four Chinese patients with biopsy proven anti-GBM disease, and have been described in patients with IgA anti-GBM [13][14][15] . A better reactivity when using the non-denaturing coating conditions in two of the present cases indicate that epitope differences do contribute to the low test results in our patients.…”

Comparison of the performance of a chemiluminescence assay and an ELISA for detection of anti-GBM antibodies

“…Approximately 2-8% of patients with anti-GBM disease have been reported to be anti-GBM antibody negative by enzyme immunoassays or Western blot [10]. The antibodies of sometimes patients may recognize highly conformational epitopes, which could be found by nonreducing Western blotting, and some may bind to a chains other than a3 [5].…”

“…The confirmative feature of anti-GBM disease is the exhibition of linear deposits of immunoglobulin G (IgG) along the GBM on renal biopsy and detectable circulating antibodies against GBM by means of commercial enzyme-linked immunosorbent assay (ELISA) kits. However, there have been some cases reported with anti-GBM antibody deposition along the GBM but without positive findings for the autoantibodies by ELISA [5]. For these patients, diagnosis was difficult to confirm, and the indicator for plasmapheresis was deficient.…”

Routinely used immunoassays do not detect circulating anti‐GBM antibodies against native NC1 hexamer and EA epitope of the α3 chain of type IV collagen

“…These commercial tests, which are often automated, are considered rapid to perform, highly sensitive (>95%) and specific (>97%) . However, IIF on primate kidney tissue pretreated with 8M urea, which allows the exposure of cryptic epitopes of type IV collagen can be useful to detect anti‐GBM antibodies . Up to now, there are no relevant data comparing IIF test using urea treatment versus other immunoassays.…”