原理免疫球蛋白(Ig)是具有抗体活性和结构相似的血清球蛋白。Ig的基本结构是四条肽链,二轻二重,肽链之间由二硫键相联结。各种Ig的轻链相同,但重链则不同。根据重链的抗原结构,可将Ig分为:IgG、IgA、IgM、IgD,和IgE五种。用木瓜酶处理,可将Ig分子裂解为氨基端二个Fab片段[(Fab)_2]与一个Fe片段。Fab是抗体与抗原结合的区域,一个Ig分子有二个Fab,所以抗体是二价的。Fe部分和Ig的其他特性(如结合补体,通过胎盘,亲细胞性和代谢特点等)有关(表1)。从表1还可看到正常健康人血清中Ig有一定含量,但在患某种疾病(如慢性感染、变态反应病、 Principle Immunoglobulins (Ig) are serum globulin that have antibody activity and structure. Ig’s basic structure is four peptide chain, two light and two, the peptide chain by the disulfide bond association. The various light chains of Ig are the same, but the heavy chains are different. According to the heavy chain antigen structure, Ig can be divided into: IgG, IgA, IgM, IgD, and IgE five. With papain enzyme, the Ig molecule can be cleaved into two amino acid terminal Fab fragment [(Fab) _2] and an Fe fragment. Fabs are the area where an antibody binds to an antigen, two Fabs per Ig molecule, so the antibody is bivalent. Fe and other Ig features (such as binding to complement, through the placenta, pro-cellular and metabolic characteristics, etc.) (Table 1). Table 1 can also be seen in normal healthy human serum Ig in a certain amount, but suffering from a disease (such as chronic infection, allergic disease,