Box 1. Immunoglobulin subclasses and oligosaccharide modifications

Differences in the amino acid sequences of different subclasses of IgG (IgG1 to IgG4 in humans) can affect their binding affinity for different classes of activating (pro-inflammatory) or inhibitory (anti-inflammatory) Fc receptors⁸⁸. Likewise, differences in the sequences of attached oligosaccharides may be critical for antibody function with the removal of terminal sialic acid resulting in increased anti-inflammatory activity^{89, 90}. Refinements of commercial immunoglobulin preparations with regard to IgG subclasses and oligosaccharide content may result in polyclonal immunoglobulin products with improved antiviral activity.