Goat polyclonal antibody to human IgG. IgG is a monomeric immunoglobulin, with two heavy chains and two light chains. IgG can be found in blood and is the most abundant immunoglobulin, constituting 75% of serum immunoglobulins in humans. There are 4 subclasses (IgG1 (66%), IgG2 (23%), IgG3 (7%) and IgG4 (4%)) that can bind to many types of pathogens, protecting the body against them by complement activation, opsonization for phagocytosis and neutralisation of their toxins.