Immunoglobulin G; Purified

Immunoglobulin G (IgG) is the most prevalent immunoglobulin in serum, accounting for approximately 75% of all immunoglobulins. It is also the most prevalent immunoglobulin in extra vascular spaces. Structurally, IgG is a monomer and four subclasses exist, based on minor differences in the amino acid sequence of the constant region of the heavy chain: IgG1, IgG2, IgG3, IgG4.

Phagocytic cells, such as macrophages, monocytes, polymorphonuclear leukocytes, and some lymphocytes have Fc receptors for IgG, primarily IgG1 and IgG3. IgG binds to an antigen, then the phagocytic cell binds to the Fc region of the IgG and internalizes the IgG-antigen complex. In this manner, IgG helps rid the body of unwanted antigens.

Elevated IgG levels are found in several different types of infection, cirrhosis of the liver, hepatitis, dysproteinemia, rheumatoid arthritis, multiple myeloma conditions, among many other disorders. Low levels of IgG are noted in several conditions, such as Bence Jones proteinemia, chronic lymphoblastic leukemia, agammaglobulinemia, lymphoid aplasia, and IgA myeloma