HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Data Supplement Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Rispens, T. Articles by Aalberse, R. C. Search for Related Content PubMed PubMed Citation Articles by Rispens, T. Articles by Aalberse, R. C. Pubmed/NCBI databases Substance via MeSH

Human IgG4 Binds to IgG4 and Conformationally Altered IgG1 via Fc-Fc Interactions

Theo Rispens^1,*,, Pleuni Ooievaar-De Heer^*,, Ellen Vermeulen^*,, Janine Schuurman, Marijn van der Neut Kolfschoten^*, and Rob C. Aalberse^*,

^* Sanquin Research, Amsterdam, The Netherlands; Landsteiner Laboratory, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands; and Genmab, Utrecht, The Netherlands

The Fc fragment of IgG4 can interact with the Fc fragment of another IgG molecule. This interaction is a confounding factor when measuring IgG4 rheumatoid factor levels. Recently, we demonstrated that half-molecules of IgG4 can exchange to form a bispecific Ab. We expected these two phenomena to be related and investigated the physicochemical aspects of IgG4 Fc-Fc interactions. We found that IgG4 is >99% monomeric by size-exclusion chromatography; therefore, IgG4 Fc-Fc interactions in the fluid phase (if any) would be short-lived. However, ¹²⁵I-labeled IgG4 does bind to IgG1 and IgG4 coupled to a solid phase. By contrast, IgG1 does not bind to coupled IgG4. Furthermore, conditions that induce partial unfolding/dissociation of the CH3 domains enhance IgG4 Fc binding, suggesting that Fc binding is primarily CH3 mediated. IgG4 slowly associates with both IgG4 and IgG1 coupled to a biosensor chip. Remarkably, subsequent dissociation was much faster for IgG4 than for IgG1. Moreover, after binding of an IgG4 mAb to Sepharose-coupled Ag, we observed additional binding of IgG4 with irrelevant specificity, whereas similar binding was not observed with Ag-bound IgG1. We propose that the IgG4-IgG4 Fc interaction resembles an intermediate of the Fab-arm (half-molecule) exchange reaction that is stabilized because one of the IgG4 molecules is coupled to a solid phase. By contrast, IgG4 Fc recognizes IgG1 only after a conformational change that renders CH3(IgG1) accessible to an interaction with the CH3(IgG4). Such Fc interactions may enhance Ag binding of IgG4 in vivo.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ Address correspondence and reprint requests to Dr. Theo Rispens, Sanquin Blood Supply Foundation, Plesmanlaan 125, 1066 CX, Amsterdam, The Netherlands. E-mail address: T.Rispens{at}sanquin.nl

² Abbreviations used in this paper: RA, rheumatoid arthritis; RF, rheumatoid factor; HP-SEC, high-performance size-exclusion chromatography; CNBr, cyanogen bromide; GSH, glutathione; RU, response unit; SPR, surface plasma resonance.

³ The online version of this article contains supplemental material.