Overview

Antibody, also known as immunoglobulin (Ig), is a glycoprotein in the immunoglobulin superfamily. They are the main components of immunoglobulin in plasma. Antibodies are usually composed of some basic units, each antibody including two long (large) heavy chains and two short (small) light chains. And the light chain and heavy chain are connected by disulfide bonds [1].

Antibody is a glycoprotein in the immunoglobulin superfamily

Basic Information

Chinese name: Antibody

Foreign name: Antibody

Property: Immunoglobulin

Distribution: in the serum and other body fluids of vertebrates

Generating cells: plasma cells (effector B cells)

Composition: mainly composed of immunoglobulin [2]

Basic terminology

Immune system（Immunkörper）

Mediator receptor（Amboceptor）

Mediator（Zwischenkörper）

Material sensitive body（substance sensibilisatrice）

connector（copula）

De's body（Desmon）

White blood cell hormone（philocytase）

Medium fixed body（fixateur）

Immunoglobulin（Immunisin）[3]

classification

1. Name: IgA, number of types: 2, shape: Y type, double Y type

2. Name: IgD, number of types: 1, shape: Y-shaped

3. Name: IgE, number of types: 1, shape: Y-shaped.

4. Name: IgG, number of types: 4, shape: Y-shaped

5. Name: IgM, number of types: 1, shape: pentagonal [4].

bioactivity

(1) Combining specific antigens

(2) Activate complement

(3) Combining cells

(4) Can pass through the placenta and mucosa

(5) Has antigenicity

(6) The resistance of antibodies to physical and chemical factors is the same as that of general globulin

Type of species

The variability of structural domains

The gene loci used to encode antibodies in chromosomes have a wide range, including genes encoding various structural domains.

V (D) J recombination

Somatic Hypermutation and Affinity Maturity Process

The recombination of immunoglobulin in somatic cells, also known as V (D) J recombination, can lead to unique changes in the variable region.

Type conversion

Immunotyping is a biological process that occurs in activated B cells, allowing the cells to produce different types of antibodies such as IgA, IgE, and IgG.

Divided by affinity

If a group of antibodies have affinity for the same antigen epitope, or for different antigen epitope molecules on the same antigen, or for different antibodies on microorganisms of the same plant type, it is called a specific effect (or single effect).

Structure and homogeneity

1、 Structure

1. Antigen binding region (Fab)

2. Antigen Crystallization Region (Fc)

3. The blue heavy chain consists of a variable region (VH), followed by a constant region (CH1), a hub region, and two other constant regions (CH2 and CH3)

4. The green light chain contains a variable region (VL) and a constant region (CL)

5. Antigen binding sites

6. Hub area [5]

Antibody structure and isotype

heavy chain

There are five types of immunoglobulin heavy chains in mammals, denoted by Greek letters: α, δ, ε, γ, and μ.

light chain

The immunoglobulin light chain consists of approximately 211 to 217 amino acids and is divided into two domains, namely the constant region and the variable region.

2、 Same type

According to the number of Y monomers and the type of heavy chain, antibodies in mammals can be classified into five isotypes: IgG, IgM, IgA, IgD, and IgE. These isoforms differ in biological characteristics, functional regions, and the ability to bind to different antigens:

function

Molecular functional regions: (1) L chain functional region, (2) H chain functional region

Activation of complement

Activation of effector cells (regulatory effect)

Agglomeration and precipitation reaction

neutralizing antibody

Difference from immunoglobulin

Initially, some people used electrophoresis to prove that the activity of antibodies in serum was in the gamma globulin portion, so antibodies were collectively referred to as gamma globulin. Later, it was discovered that antibodies were not all located in the gamma region; And the globulin located in the gamma region may not necessarily have antibody activity.

In 1964, the World Health Organization held a special meeting to collectively refer to immunoglobulin (Ig), which contains antibody activity and is associated with antibodies, such as abnormal immunoglobulins present in the serum of patients with myeloma, macroglobulinemia, cryoglobulinemia, and naturally occurring immunoglobulin subunits in normal individuals. Therefore, immunoglobulin is a concept of structural chemistry, while antibodies are a concept of biological function. It can be said that all antibodies are immunoglobulins, but not all immunoglobulins are antibodies.

Variable zone and constant zone

(1) Variable region (V region)

(2) Constant region (C region)

Enzymatic fragment

1. Papain enzyme cleavage fragments

2. Pepsin enzyme cleavage fragments

Polyclonal monoclonal antibodies

polyclonal antibody

monoclonal antibody

Autoantibodies and related diseases

Anti double helix DNA: Systemic lupus erythematosus

Anti exosome complex: sclerosing myositis

Anti Ro or La protein: Systemic lupus erythematosus, infantile atrioventricular block, primary Sjogren's syndrome

Anti Smith antigen: Systemic lupus erythematosus

Antiphospholipid: Antiphospholipid syndrome

Anti single chain annealing protein or single chain binding protein: Sjogren's syndrome

Anti neutrophil cytoplasm (c-ANCA): Wagner's granulomatosis

Antineutrophilic peripheral neuropathy (p-ANCA): Microscopic polyangitis, Churg Strauss syndrome, systemic vasculitis (non-specific), nodular polyarteritis (unconfirmed)

Anti IgG (rheumatoid factor): rheumatoid arthritis

Anti centromere: scleroderma

Anti topoisomerase: scleroderma

Anti smooth muscle: chronic autoimmune hepatitis

Anti mitochondrial: Primary biliary cirrhosis

Nicotine resistant acetylcholine receptor: myasthenia gravis

Voltage controlled gate calcium ion channel: Lambert Eaton syndrome

Anti thyroid peroxidase (microsomal) Hashimoto's thyroiditis

Anti TSH receptor: Graves' disease

Anti Hu protein: paraneoplastic cerebellar syndrome

Voltage controlled gate potassium ion channel (VGKC): Borderline encephalitis

Anti-N-methyl-D-aspartate receptor (NMDA): encephalitis [6]

Related inspections

antinuclear antibody

Serum anti Japanese encephalitis virus antibody

Serum anti cytomegalovirus antibody

Serum hepatitis B antigen antibody

Serum hepatitis E antibody

Serum EB virus antibody

Blood mycoplasma antibody

Serum hepatitis B surface antibody

Serum hepatitis C antibody