Immunoglobulin (Ig) refers to a globulin that has the activity or chemical structure of an antibody (Ab) and is similar to the antibody molecule. Immunoglobulins are a tetrapeptide chain structure consisting of two identical light chains and two identical heavy chains linked by interchain disulphide bonds. Immunoglobulins are divided into five categories, namely immunoglobulin G (IgG), immunoglobulin A (IgA), immunoglobulin M (IgM), immunoglobulin D (IgD) and immunoglobulin E (IgE).
