IgG2

IgG2 is one of the four human IgG subclasses. It is produced by B cells after class switch recombination and circulates in serum as a monomer. It constitutes a significant portion of total IgG and is encoded by the IGHG2 gene in the IGH locus on chromosome 14.

IgG2 antibodies have a relatively short hinge region that confers rigidity. Compared with IgG1 and IgG3, the Fc region of IgG2 binds Fc gamma receptors with lower affinity and has a reduced ability to activate the classical complement pathway via C1q.

IgG2 responses are particularly prominent to carbohydrate-based antigens, such as polysaccharide capsules of bacteria. The IgG2 response is often generated in response to T-independent antigens and supports defense against encapsulated pathogens, though high-affinity responses to protein antigens are more associated with other subclasses.

Low levels of IgG2, or selective IgG2 deficiency, can predispose individuals to recurrent infections with encapsulated bacteria and poor responses to polysaccharide vaccines. Evaluation of suspected deficiency includes measurement of IgG subclass concentrations and assessment of vaccine-specific antibody responses.

The IGHG2 gene is part of the human heavy-chain constant region cluster on chromosome 14. There are genetic variants and allotypes within the IgG2 subclass that can influence function or measurement.

In medical practice, pooled IgG therapies contain IgG2 along with other subclasses, contributing to broad protective activity.