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IgG subclasses and allotypes: from structure to effector functions.

Frontiers in immunology (2014-11-05)
Gestur Vidarsson, Gillian Dekkers, Theo Rispens
ABSTRACT

Of the five immunoglobulin isotypes, immunoglobulin G (IgG) is most abundant in human serum. The four subclasses, IgG1, IgG2, IgG3, and IgG4, which are highly conserved, differ in their constant region, particularly in their hinges and upper CH2 domains. These regions are involved in binding to both IgG-Fc receptors (FcγR) and C1q. As a result, the different subclasses have different effector functions, both in terms of triggering FcγR-expressing cells, resulting in phagocytosis or antibody-dependent cell-mediated cytotoxicity, and activating complement. The Fc-regions also contain a binding epitope for the neonatal Fc receptor (FcRn), responsible for the extended half-life, placental transport, and bidirectional transport of IgG to mucosal surfaces. However, FcRn is also expressed in myeloid cells, where it participates in both phagocytosis and antigen presentation together with classical FcγR and complement. How these properties, IgG-polymorphisms and post-translational modification of the antibodies in the form of glycosylation, affect IgG-function will be the focus of the current review.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
IgG from sheep serum, reagent grade, ≥95% (SDS-PAGE), essentially salt-free, lyophilized powder
Sigma-Aldrich
IgG1, Kappa from murine myeloma, clone MOPC 21, purified immunoglobulin, buffered aqueous solution
Sigma-Aldrich
Anti-human IgG (1mg) KC, from mouse
Sigma-Aldrich
Human IgG, Fab Fragment, Plasma
Sigma-Aldrich
Mouse IgG1 ELISA Kit
Sigma-Aldrich
IgG from rat serum, technical grade, ≥80% (SDS-PAGE), buffered aqueous solution
Sigma-Aldrich
IgG from rat serum, reagent grade, ≥95% (SDS-PAGE), essentially salt-free, lyophilized powder
Sigma-Aldrich
IgG3, Lambda from murine myeloma, clone Y5606, purified immunoglobulin, buffered aqueous solution