Immunoglobulins are a class of proteins with antibody activity in serum and body fluids, which can be classified into five major categories, and are characterized by anti-infection, used for early diagnosis, and causing hypersensitivity reactions. 1. Immunoglobulin G: It is the most abundant immunoglobulin in human blood, which can pass the placental barrier, has antibody activity against viruses, bacteria and parasites, and has a longer duration of action in fighting infections. 2. Immunoglobulin M: It is the earliest antibody appearing in the initial humoral immune response and has the largest molecular weight and the strongest ability to activate complement, which is involved in autoimmune diseases and hypersensitivity reactions, and can also be used in the early diagnosis of infections. 3. Immunoglobulin A: it can be divided into serum type and secretion type, which mainly exists in the mucous membrane surface of respiratory tract, digestive tract, genitourinary tract and breast milk, and can participate in the immunity of local mucous membrane. 4. Immunoglobulin D: its immune function is not completely clear, it may react with certain antigens, or it may be related to hypersensitivity reaction, it is the sign of B cell differentiation and maturity. 5. Immunoglobulin E: It is the least abundant immunoglobulin in normal human serum, and it can bind to allergens and cause hypersensitivity reactions, in addition, it is also related to parasite immunity. If immunoglobulin abnormality occurs, it is recommended to consult a doctor in time to clarify the cause and follow the doctor’s instructions for treatment.