There are four types of immunoglobulins in rats: IgA, IgE, IgM and IgG. Immunoglobulin G (IgG) is the most important form of immunoglobulin in serum, accounting for about 75% of the total content of immunoglobulins in serum, and it mainly participates in the recognition and elimination of pathogens and toxic substances, and has antiviral, antimicrobial agent, and immunomodulatory functions. IgG is a macromolecular glycoprotein with a molecular weight of 150 kDa, consisting of two light chains and two heavy chains, each of which is linked by a disulfide bond. is a macromolecular glycoprotein with a molecular weight of 150 kDa, consisting of two light chains and two heavy chains, each of which is connected to the other by a disulfide bond, forming a tetrameric quaternary structure. The resulting tetramer forms two identical hemispheres that together form a Y-like structure. The amino terminus, with its highly variable amino acid composition, is involved in antigen binding, whereas the constant portion of the C-terminus is involved in complement binding, placental passage, and cell membrane binding. In the rat, the IgG class is further divided into four subclasses: IgG1, IgG2a, IgG2b, and IgG2c.