Serum immunoglobulins are proteins with antibody activity in the body, mainly divided into five categories, including IgA, IgG, IgM, IgD and IgE. Immunoglobulins are mainly found in blood, body fluids and tissues in the body, and when bacteria or viruses invade the body, immunoglobulins can effectively play a defensive role, so immunoglobulins have a protective function for the body. Immunoglobulins are usually referred to as IgA, IgG and IgM, and their levels in the serum reflect the level of immunoglobulins in the serum.