Terms about structure and function of antibodies

  1. Antibody

An antibody refers to a protective protein produced by the body due to stimulation of an antigen. It is a large Y-shaped protein secreted by plasma cells (effector B cells) that is used by the immune system to identify and neutralize foreign substances such as bacteria, viruses, etc. Antibodies can recognize a unique feature of a particular foreign object (an antigen).

  1. Antibody engineering

Antibody engineering refers to the process of transforming and reassembling antibody genes by using recombinant DNA and protein engineering techniques, expressing antibody molecules after transfecting appropriate recipient cells, or modifying antibody molecules by cell fusion or chemical modification. These antibody engineered antibody molecules are novel antibody molecules that are reassembled according to human design, which can retain (or increase) the specificity and major biological activity of natural antibodies, remove (or reduce or replace) irrelevant structures.

  1. Immunoglobulin (lg)

An immunoglobulin has an antibody activity and similar chemical structure to an antibody.

  1. Functional region

The H chain and L chain of the lg molecule can be folded into several spherical structures by intrachain disulfide bonds, and each spherical structure consists of 110 amino acids, which has a certain physiological function and is called a functional region, also called the domain.

  1. Variability

The variability of a position is the ratio of the number of different amino acids present at that position to the frequency of occurrence of the most frequently occurring amino acid residues at that position.

  1. Immunoglobulin superfamily (IGSF)

IGSF is a collection of molecules containing immunoglobulin folded structurally-like functional region. Most members of the lg molecular superfamily are cell membrane surface molecules.

  1. Classification according to the antigen characteristics of immunoglobulin

1) Isotype: refers to the antigen specificity of antibodies shared by all individuals in the same species, present in the constant region. Isotype antigen specificity varies by species, mainly including lg class, industry, type and business type.

2) Allotype: refers to the different antigen specificity of lg molecules between individuals of the same genus. As a genetic marker, there is a constant region of lg.

3) Unique type: each antibody forms an antigen specificity specific to the antibody molecule produced by the cell clone. It is determined by the difference in the amino acid sequence of the VH or VL variable region. It is closely related to the specificity of the antibody-binding antigen.

  1. CDR epitopes

VH and VL are tightly bound together to form a dense globular structure, which becomes the Fv segment. The six CDRs are located at the N-terminus of the Pv segment and are called CDR surfaces, ie, antigen binding sites.

  1. Binding force

The combination of antigen and antibody depends on electrostatic attraction, hydrogen bonding, van der Waals force, etc., and requires suitable temperature, pH, ionic strength and intact antibody. This combination is reversible.

  1. Antibody-dependent cell cytotoxicity (ADCC)

The antibody molecule binds to the surface of the target cell and can be combined with the Fc receptor on the surface of the killer cell to promote the pair. The killing effect of target cells is called ADCC. Mononuclear macrophages, neutrophils and NK cells have ADCC effect.