IGHG3 and infection: Its function is to bind many types of pathogens such asviruses, bacteria and fungi, and protect the body from infection.[6]IgG subclass proportions are tightly controlled within a narrow range:IgG1 (60 - 65%); IgG2 (20 - 25%); IgG3 (5 - 10%); and IgG4 (3 - 6%)of total IgG.