Structure and function of antibodies

Research lines


In this line of research, we address basic immunological issues (immunogenicity, tolerance) as well as strive to develop tools for optimizing treatment with therapeutic antibodies. The research is highly collaborative, involving different divisions of Sanquin (R, D, REA), clinical partners in Amsterdam (G. Wolbink, rheumatology, Reade; J. Killestein, neurology, VUMc; G.D'Haens, gasteroenterology, AMC) and numerous international collaborations. 

Sanquin has a unique and prominent position as centre of expertise with respect to immunogenicity of biologics, monitoring drug levels and anti-drug antibodies, and surveillance of treatment with biologics in a post-marketing setting. Service testing, for routine diagnostics as well as (phase VI) clinical trials, and diagnostic kits, is available https://www.sanquin.org/products-and-services/bioanalysis-of-biologics/index Continued development of novel assays in conjunction with exploring their clinical usefulness is key to maintain and expand this position. A major contribution to this success is the unique combination of close collaborations with clinical partners, the ability to develop assays in-house and bring them to GCLP level to support clinical trials, and a strong embedding within the basic immunological research of Sanquin. 

Biology of IgG4

IgG4 antibodies are unusual in many aspects. They develop typically only in the absence of infection, often to food antigens, or during immunotherapy, and are associated with alleviation of allergic symptoms in the latter case. Furthermore, therapeutic proteins such as FVIII or adalimumab are known to elicit antibodies in part of the patients, and these antibody responses can be highly IgG4-skewed. In these situations, blocking of the target is causing non-response, and such antibody responses are therefore undesired. The same holds true for IgG4 autoantibodies, which may play a role in pathogenesis because by binding to the target they interfere with its function, e.g. in case of autoantibodies to desmogleins in pemphigus vulgaris. 

While our understanding of the structural and functional aspects has advanced in recent years, the role of IgG4 in various diseases often remains elusive. Furthermore, the regulation of IgG4 responses is still incompletely understood. IgG4 antibody responses generally require prolonged or repeated challenge with antigen for reasons that are not yet known. This hampers both the development of protocols to swiftly induce desired IgG4 responses (e.g., to relieve allergic symptoms) as well as to avoid unwanted IgG4 responses such as those induced by therapeutic proteins. Unraveling the intricacies of IgG4 development may provide clues as how to overcome these issues. We have investigated many aspects of IgG4 biology in the past years, in particular with respect to Fab arm exchange. Furthermore, we initiated the analysis of IgG4 B cell responses, and investigated the phenotype of IgG4 memory B cells. This led to a number of interesting observations: IgG4 B cells express more FcεRII compared to IgG1 B cells, possibly resulting in an altered responsiveness to IgE-containing immune complexes. Furthermore, a Th2-like milieu is linked to a distinct pattern of expression of chemokine receptors, suggesting that IgG4 B cells are programmed to migrate differentially to lymphoid or inflamed tissue, a finding that is support by analysis of tissue samples. 

Major issues that need to be addressed include: 

  • Regulation of IgG4 B cell responses
  • Role of IgG4 in IgG4-related disease
  • Why are some autoantibodies IgG4?
  • In vivo mechanism of Fab arm exchange
  • Biological activity after Fab arm exchange

Our investigations towards the structural peculiarities of IgG4 has led to the discovery that allotypic variations in human IgG can have profound effects on the stability of these molecules; in particular, IgG3 allotypes differ fundamentally in the strength of the CH3-CH3 interactions. Although the functional consequences of these are unknown, discrepancies exist in the literature showing either superior effector functions (either complement or FcγR mediated) of IgG3 compared to IgG1, or vice versa, that may in part be related to allotype differences. Together with G. Vidarsson and J. Schuurman (Genmab), we are systematically exploring the functional consequences of human immunoglobulin allotypes. 
Furthermore, we continue our work on unraveling the biology of IgG4 antibodies and IgG4 B cell responses as part of the research on B cell biology in the group of M. van Ham, and continue our collaborations with E. Culver/E. Barnes, Oxford on IgG4-related disease.  

Antibodies to antibodies in RA

Autoantibodies are a characteristic feature of RA. These include the rheumatoid factor (RF), one of the first autoantibodies to be discovered but still poorly understood, anti-citrullinated protein antibodies (ACPAs), another heterogeneous pool of autoantibodies that bind to citrullinated proteins that likely represent neo-epitopes, and anti-hinge antibodies, which bind proteolytic fragments of IgG that may be formed during inflammation. The potential role of the different autoantibodies that have been described in RA in pathogenesis is far from clear. This may on the one hand be attributed to the heterogenic nature of these antibody responses: multiple specificities of RF, ACPAs, and anti-hinge can be distinguished, and on the other hand because these different antibodies have largely been studied in isolation, whereas two of the three types of antibodies will bind to antibodies and therefore affect the types of immune complexes that will be formed. Indeed, previous work has demonstrated that the presence of both RF and ACPA predicts a more severe disease state.

In this line of research, we aim to study the biology of auto-anti-antibodies in RA in relation to pathogenesis. On the one hand, we aim to define epitopes of RF and anti-hinge, and to fingerprint patients using multiplex-based technology. Improved characterization of the rheumatoid factor response and associated autoantibody responses in RA may be used to determine risk of onset of disease and predict severity of disease and response to treatment. Currently used assays for autoantibodies are limited in scope and specificity. The evaluation of the RF response is often limited to the measurement of serum levels of IgM-RF recognizing polyclonal human or rabbit IgG. By improving the characterization of rheumatoid factors and other autoantibodies, we will develop new diagnostic methods and stratifying tools to identify subpopulations of patients with different stages of disease, different characteristics of progression of the disease and different responses to treatment. To achieve this we will use a multiplex approach to autoantibody characterization using a 96-spot biosensor platform (IBIS). We will improve the characterization of the RF response by looking at isotype, subclass- and allotype specificity, avidity and interaction / complex formation with ACPA and other RA associated antibodies. We expect that better characterization of RF and associated autoantibodies responses will lead to a better distinction between “pathological” and “non-pathological” autoantibodies.

On the other hand, we aim to study immune complex formation of RF and anti-hinge with ACPAs, study how this affects immune activation as compared to these antibodies in isolation. We anticipate that the basic biology of rheumatoid factors cannot be understood unless in relationship with other autoantibodies and immune complex formation. If true, this hypothesis can for the first time explain the role of RF in RA.

Fab glycosylation

Besides conserved IgG Fc glycans, about 15% of serum IgG contains glycans within the variable domains. Antibodies can acquire N-linked glycans in the variable (Fab) domains during antigen-specific immune responses. These glycans have received little attention, but in recent years, a number of studies have suggested that Fab glycans may be an important feature of IgG. For instance, IVIg enriched for Fab glycans has been reported to possess altered immunomodulatory properties based on in vitro culture experiments with DCs or B cells. Therefore, we hypothesize that Fab glycans represent an essential aspect of antibody biology. In this line of research, we investigate the potential roles of Fab glycosylation in shaping the function of antibodies. 

Key publications

  • Berkhout LC, l'Ami MJ, Ruwaard J, Hart MH, Heer PO, Bloem K, Nurmohamed MT, van Vollenhoven RF, Boers M, Alvarez DF, Smith CH, Wolbink GJ, Rispens T. Dynamics of circulating TNF during adalimumab treatment using a drug-tolerant TNF assay. Sci Transl Med. 2019 Jan 30;11(477)
  • van de Bovenkamp FS, Derksen NIL, Ooijevaar-de Heer P, van Schie KA, Kruithof S, Berkowska MA, van der Schoot CE, IJspeert H, van der Burg M, Gils A, Hafkenscheid L, Toes REM, Rombouts Y, Plomp R, Wuhrer M, van Ham SM, Vidarsson G, Rispens T. Adaptive antibody diversification through N-linked glycosylation of the immunoglobulin variable region.  Proc Natl Acad Sci U S A. 2018; 115(8):1901-1906
  • l'Ami MJ, Krieckaert CL, Nurmohamed MT, van Vollenhoven RF, Rispens T, Boers M, Wolbink GJ. Successful reduction of overexposure in patients with rheumatoid arthritis with high serum adalimumabconcentrations: an open-label, non-inferiority, randomised clinical trial.  Ann Rheum Dis. 2017 211781.
  • van Schie KA, Ooijevaar-De Heer P, Kruithof S, Plasencia C, Jurado T, Pascual Salcedo D, Brandse JF, d'Haens GR, Wolbink GJ, Rispens T. Infusion reactions during infliximab treatment are not associated with IgE anti-infliximab antibodies. Infusion reactions during infliximab treatment are not associated with IgE anti-infliximab antibodies. Ann Rheum Dis. 2017 Jul;76(7):1285-1288.
  • Van Schie KA, Kruithof S, van Schouwenburg PA, Vennegoor A, Killestein J, Wolbink G, Rispens T. Neutralizing capacity of monoclonal and polyclonal anti-natalizumab antibodies: the immune response to antibody therapeutics preferentially targets the antigen binding site. J Allergy Clin Immunol. 2017, 139:1035-1037
  • Falkenburg WJ, van Schaardenburg D, Ooijevaar-de Heer P, Wolbink G, Rispens T. IgG Subclass Specificity Discriminates Restricted IgM Rheumatoid Factor Responses From More Mature Anti-Citrullinated Protein Antibody-Associated or Isotype-Switched IgA Responses. Arthritis Rheumatol. 2015 Dec;67(12):3124-34
  • Bloem K, van Leeuwen A, Verbeek G, Nurmohamed MT, Wolbink GJ, van der Kleij D, Rispens T. Systematic comparison of drug-tolerant assays for anti-drug antibodies in a cohort of adalimumab-treated rheumatoid arthritis patients. J Immunol Methods. 2015,418, 29-38
  • Van Schie KA, Hart MH, de Groot ER, Kruithof S, Aarden LA, Wolbink GJ , Rispens T. The antibody response against human and chimeric anti-TNF therapeutic antibodies primarily targets the TNF binding region. Ann. Rheum. Dis. 2015, 74, 311-314
  • Lighaam LC, Vermeulen E, Bleker Td, Meijlink KJ, Aalberse RC, Barnes E, Culver EL, van Ham SM, Rispens T. Phenotypic differences between IgG4+ and IgG1+ B cells point to distinct regulation of the IgG4 response.  J Allergy Clin Immunol. 2014 Jan;133(1):267-70.e1-6.
  • Rispens T, Ooijevaar-de Heer P, Bende O, Aalberse RC. Mechanism of immunoglobulin G4 Fab-arm exchange. J Am Chem Soc. 2011 Jul 6;133(26):10302-11