Biology subjects

Barendregt, A.

Publications and source records attributed to Barendregt, A..

3 recordsLinked to original sources

bioRxiv2026

IgG4 antibody repertoire diversity is stable over several years in health and autoimmune disease

Despite its relative anti-inflammatory nature, IgG4 is involved in a variety of pathological conditions such as autoimmune disease and cancer. To investigate whether the IgG4 repertoire presents any abnormalities in diseases where IgG4 autoantibodies predominate, we charted longitudinal IgG4 repertoires in health, in an IgG4-mediated autoimmune disease (AID; muscle-specific kinase myasthenia gravis (MuSK MG)), and in IgG1/IgG3 mediated AIDs (acetylcholine receptor (AChR) MG and Lambert-Eaton myasthenic syndrome (LEMS). In total, we assessed 218 samples of 69 donors using mass spectrometry-based antibody repertoire analysis, covering a timespan of up to eight years. Despite being superficially inconspicuous in clonal diversity and abundances, we detected a slightly elevated number of IgG4 clones in MuSK MG patients compared to healthy donors. Notably, this observation did not coincide with drastic repertoire changes during treatment, suggesting that a large portion of the IgG4 repertoire is not significantly affected by common MuSK MG treatment regimens. Comparing the IgG4 antibody repertoires of all donors, we found that they were exceptionally unique for each individual. Against what would be expected in the case of a constantly adapting antibody repertoire, a large portion of the IgG4 clones remained stable without any further maturation. This observation even extended to patients receiving B cell depleting or IgG modulating treatments. Our findings suggest that a dominating fraction of the IgG4 pool may be produced by long-lived plasma cells, which are unaffected by disease or medical interventions.

immunology↗

bioRxiv2023

CD5L is a canonical component of circulatory IgM

Immunoglobulin M (IgM) is an evolutionary conserved key component of humoral immunity, and the first antibody isotype to emerge during an immune response. IgM is a large (1 MDa), multimeric protein, for which both hexameric and pentameric structures have been described, the latter additionally containing a joining (J) chain. Using a combination of single-particle mass spectrometry and mass photometry, proteomics and immunochemical assays, we here demonstrate that circulatory (serum) IgM exclusively exists as a complex of J-chain-containing pentamers covalently bound to the small CD5 antigen-like (CD5L, 36 kDa) protein. In sharp contrast, secretory IgM in saliva and milk is principally devoid of CD5L. Unlike IgM itself, CD5L is not produced by B cells, implying that it associates with IgM in the extracellular space. We demonstrate that CD5L integration has functional implications, i.e., it diminishes IgM binding to two of its receptors, the Fc{micro}R and the polymeric Immunoglobulin receptor (pIgR). On the other hand, binding to Fc{micro}R as well as complement activation via C1q seem unaffected by CD5L integration. Taken together, we redefine the composition of circulatory IgM as a J-chain containing pentamer, always in complex with CD5L.

molecular biology↗

bioRxiv2022

Humans have distinct repertoires of IgA1

The most abundant immunoglobulin present in the human body is IgA1. It has the highest concentrations at the mucosal lining and in biofluids such as milk and is the second most abundant class of antibodies in serum. We assessed the structural diversity and clonal repertoire of IgA1-containing molecular assemblies longitudinally in human serum and milk from three donors using a mass spectrometry-based approach. IgA-containing molecules purified from serum or milk were assessed by the release and subsequent analysis of their Fab fragments. Our data revealed that serum IgA1 consists of two distinct structural populations, namely monomeric IgA1 ([~] 80%) and dimeric joining (J-) chain coupled IgA1 ([~] 20%). Also, we confirmed that IgA1 in milk is present solely as secretory (S)IgA, consisting of two ([~] 50%), three ([~] 33%) or four ([~] 17%) IgA1 molecules assembled with a J-chain and secretory component (SC). Interestingly, the serum and milk IgA1-Fab repertoires were distinct between monomeric, and J-chain coupled dimeric IgA1. The serum dimeric J-chain coupled IgA1 repertoire contained several abundant clones also observed in the milk IgA1 repertoire. The latter repertoire had little to no overlap with the serum monomeric IgA1 repertoire. This suggests that human IgA1s have (at least) two distinct origins; one of these produces dimeric J-chain coupled IgA1 molecules, shared in human serum and milk, and another produces monomeric IgA1 ending up exclusively in serum.

immunology↗