Serum protein types refer to the genetic polymorphisms of proteins in the serum, which is the liquid portion of blood containing proteins, organic substances, inorganic salts, and water. Key serum protein types include immunoglobulins, serum enzymes, and complement proteins. Among these, immunoglobulins exhibit the most significant genetic polymorphisms, mainly seen in allotypes, which are variations in the amino acid sequences of the C regions of immunoglobulin heavy and light chains. These variations arise from mutations in the genes encoding immunoglobulins, leading to differences in antigenicity among individuals. Human immunoglobulin allotypes include Gm, Am, and Km, associated with IgG, IgA, and the κ chain, respectively. In addition to immunoglobulins, serum enzymes and complement proteins also exhibit genetic polymorphisms, affecting enzyme activity, stability, and complement function, which are important for understanding individual immune differences and disease susceptibility.