IgG sub-classes present different, well-defined N-glycan isomers

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All subclasses of human immunoglobulin G (IgG) have a conserved N- glycosylation site at Asn297, which is in the CH2 domain, and the specific glycan isomer attached significantly affects IgG functionality, impacting immune responses and therapeutic efficacy in medical applications. This suggests strong cellular regulation of glycosylation patterns could be valuable for the development of antibody-based therapeutics and biomarkers for disease.

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Using nano-HILIC-LC-MS/MS, Wang et al.¹ have identified unique distinctive glycosylation patterns for each IgG subclass that are only detectable when considering specific glycan isomers. They show that IgG1 and IgG3 have predominant galactosylation on their 6-branched glycans, IgG2 on the 3-branched glycans, and IgG4 exhibits a balanced profile.¹ These differences suggest the need for deeper exploration into links between the attached glycan isomer and the respective biological function. For example, IgG1 and IgG3 are recognized as activators of Fc-mediated effector mechanisms, such as ADCC, CDC, and ADCP, while IgG2 and IgG4 tend to elicit more subtle immune responses. Developing a detailed understanding of the effect of glycosylation on the function of IgG requires analytical approaches that can distinguish subtly different isomers.

The Isospec Analytics Approach: Cryo-IR Spectroscopy

At Isospec Analytics, we have developed a powerful approach to glycan isomer identification.^2-5 By measuring a cryogenic infrared (IR) spectrum of glycans inside a mass spectrometer after LC or IMS separation, we provide an intrinsic fingerprint that is unique to a particular isomer. Such an information-rich spectrum allows us to identify specific glycan isomers with absolute certainty. Moreover, in the absence of standards, assignments of glycan IR spectra can be achieved by measuring spectra of isomer-specific glycan fragments.

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To find out more about this powerful approach to glycan isomer identification, please contact us at info@isospec.bio.

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(1) Wang, W.; Maliepaard, J. C. L.; Damelang, T.; Vidarsson, G.; Heck, A. J. R.; Reiding, K. R. Human IgG Subclasses Differ in the Structural Elements of Their N-Glycosylation. ACS Central Science 2024, xx, xxxx. DOI: 10.1021/acscentsci.4c01157.

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(2) Abikhodr, A. H.; Warnke, S.; Ben Faleh, A.; Rizzo, T. R. Combining Liquid Chromatography and Cryogenic IR Spectroscopy in Real Time for the Analysis of Oligosaccharides. Anal. Chem. 2024. DOI: 10.1021/acs.analchem.3c03578.

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(3) Bansal, P.; Ben Faleh, A.; Warnke, S.; Rizzo, T. R. Multistage Ion Mobility Spectrometry Combined with Infrared Spectroscopy for Glycan Analysis. J. Am. Soc. Mass Spectrom. 2023, Article; Early Access. DOI: 10.1021/jasms.2c00361.

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(4) Ben Faleh, A.; Warnke, S.; Bansal, P.; Pellegrinelli, R. P.; Dyukova, I.; Rizzo, T. R. Identification of Mobility-Resolved N-Glycan Isomers. Anal. Chem. 2022, 94 (28), 10101-10108. DOI: 10.1021/acs.analchem.2c01181.

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(5) Dyukova, I.; Ben Faleh, A.; Warnke, S.; Yalovenko, N.; Yatsyna, V.; Bansal, P.; Rizzo, T. R. A new approach for identifying positional isomers of glycans cleaved from monoclonal antibodies. Analyst 2021, 146 (15), 4789-4795.

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