The variable domain is a region in which the immunoglobulin light chain and the heavy chain vary greatly near the N-terminal amino acid sequence. An immunoglobulin refers to an animal protein having antibody activity. It is mainly found in plasma and is also found in other body fluids, tissues and some secretions. Most of the immunoglobulins in human plasma are present in gamma globulin (gamma-globulin). Immunoglobulins can be classified into five classes: IgG, IgA, IgM, IgD, and IgE. It consists of two identical light chains and two identical heavy chains and is an important class of immune effector molecules.
The basic structure of the Ig molecule consists of a tetrapeptide chain consisting of two identical light chain chains of smaller molecular weight (L chain) and two identical heavy chain heavy chains (H chains). The L chain and the H chain are disulfide-bonded to form a tetrapeptide chain molecule, a monomer called an Ig molecule, which is a basic structure constituting an immunoglobulin molecule. It is known that the H chain of IgG, IgA and IgD in each of the five immunoglobulins has one variable region (VH) and three constant regions (CH1, CH2 and CH3) in total.
The main function of Ig is to combine with antigens (including foreign and self) to effectively remove foreign bodies such as microorganisms and parasites invading the body. Antibodies are antigen-specific and antigen-specific. Combined protein. Each antibody binds to a specific epitope. This combination can inactivate the antigen, but it may also be ineffective, but it may also cause pathological damage to the body, such as anti-nuclear antibodies, anti-double-stranded DNA antibodies, anti-thyroglobulin antibodies, and other autoantibodies. The characteristic of the Ig variable region is that the amino acid species, arrangement order and configuration variation of the region are large.
According to the target, it can be divided into anti-toxin, anti-bacterial antibody, anti-viral antibody and pro-cell antibody (immunoglobulin capable of binding to cells, such as lgE-reactive antibody in type 1 allergy, which can be adsorbed on the target cell membrane).
1. Heterogeneity of antibodies. The composition of antibodies is extremely complex and consists of thousands of different immunoglobulin (Ig) molecules. These Ig molecules are similar and different in shape, size, structure, and composition and arrangement of amino acids. Due to differences, their electrophoretic activity varies greatly.
2. The antibodies in the serum of any normal human are all a mixture of thousands of immunoglobulin molecules with various idiotype antigenicities. The κ chain and the λ chain can be combined with various types and subclasses. The heavy chain and the light chain have various isoforms, and the Ig produced by each clone has its own unique type.
Ig class switching: In the process of antibody response, after the antigen activates B cells, the Ig class expressed and secreted on the membrane will be converted from IgM to Ig of other classes or subclasses such as IgG, IgA, IgE, also known as the same species. Type conversion. At this time, the Ig variable region is unchanged, that is, the specificity of the binding antigen is the same, but the heavy chain type (constant region) is changed.
Other related services:
No comments:
Post a Comment