20 19 basic medical knowledge: analysis of the characteristics of five immunoglobulins

? 20 19 Tianjin Hospital Recruitment | Physical Examination Announcement and Publicity Summary (continuously updated)

The following are five types of immunoglobulins and their corresponding characteristics.

I. IgG

It is the main antibody component in serum and extracellular fluid, and its serum concentration from high to low is IgG 1, IgG2, IgG3 and IgG4. IgG is the main antibody produced again by humoral immune response, which has high affinity and is widely distributed in the body and has important immune function. IgG 1, IgG3 and IgG4 can cross the placental barrier. IgG 1, IgG2 and IgG4 can bind to staphylococcal protein A in their Fc segments. IgG 1 and IgG3 can effectively activate complement; Some autoantibodies and antibodies that cause type ⅱ and type ⅲ hypersensitivity also belong to IgG.

Two. Immunoglobulin m

It is the main component of BCR, and its secretory form is pentamer, which cannot penetrate the blood vessel wall and mainly exists in serum. The natural blood group antibody is IgM, and severe hemolysis will occur in blood transfusion with incompatible blood groups. IgM is the earliest antibody synthesized by individual development, and the fetus can produce IgM in the later stage of embryonic development. It is also the earliest antibody in humoral immune response and can be used for early diagnosis of infection.

Three. immunoglobulin a

It can be divided into serotype and secretory type. Serotype is haplotype, which mainly exists in serum; Secretory type is dimer, which mainly exists in milk, saliva, tears and mucosal surfaces of respiratory tract, digestive tract and reproductive tract, and participates in local mucosal immunity. Neonates are prone to respiratory and digestive tract infections, which may be related to insufficient synthesis of secretory IgA. Babies can get sIgA from breast milk, which is an important natural passive immunity.

Four. IgD

It can be divided into serotype and membrane-bound type, in which mIgD is an important part of BCR and a sign of cell differentiation and maturity.

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It is the immunoglobulin with the least content in normal human serum and has strong cytotropism, so it can cause type I hypersensitivity. In addition, IgE may be related to the anti-parasitic immunity of antibodies.

Among the above knowledge points, the examination of public institutions mainly examines the knowledge points of drawing wavy lines, and I hope everyone will focus on it. Then, in the future examination study and lesson preparation of public institutions, we should do the same type of real questions as this examination in time, understand the examination subjects, the proportion and difficulty of real questions, and arrange our review time reasonably according to the degree of real questions. Under normal circumstances, the number of questions in the immunology exam is relatively small, so when preparing for the exam, we should focus on reviewing the knowledge points that may give questions, and don't position the learning direction in a difficult, biased and strange direction. I hope the above summary will be helpful to everyone.

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