Antigens, antibodies, chromogenic or luminescent substrates and biological buffers are usually used in the in vitro diagnostic test kit, and the core of them is the various antibodies in the kit. So what are the commonly used antibodies?
It is a large Y-shaped immunoglobulin secreted by plasma cells (effector B cells) and can specifically bind to antigens, which is used by the immune system to identify and neutralize foreign substances such as bacteria and viruses. According to their reaction forms, antibodies can be divided into agglutinin, sedimentin, antitoxin, lysin, opsonin, neutralizing antibody, complement binding antibody, etc. There are normal antibodies (natural antibodies) and immune antibodies (such as microbial antibodies).
The function of antibody is very extensive, such as neutralizing toxin and preventing pathogen invasion, activating complement to produce membrane attacking complex to make cells dissolve and destroy, regulating phagocytosis and ADCC, mediating type I hypersensitivity reaction, crossing placenta barrier and mucosa, etc.
X-ray crystallography showed that Ig consists of four polypeptide chains connected by disulfide bonds. Ig can form "Y" structure, called Ig monomer, which is the basic unit of antibody. The natural Ig molecule contains four heteropolypeptide chains, two heavy chains (H) and two light chains (L).
The regions near the N-terminal amino acid sequence of Ig light chain and heavy chain are called variable region (V), accounting for 1 / 4 and 1 / 2 of heavy chain and light chain respectively; the regions near the C-terminal amino acid sequence are relatively stable, called constant region (c), accounting for 3 / 4 and 1 / 2 of heavy chain and light chain respectively.
The hinge region is located between ch1 and CH2, which is rich in proline and easy to stretch and bend, thus changing the distance between antigen binding sites, which is conducive to antibody binding to antigen epitopes at different locations. The hinge region is easily hydrolyzed by papain and pepsin.
Desheng technology has been developing and producing in vitro diagnostic reagents for blood detection since 2005. It has a deep research on the new Trinder's reagent, biological buffer and chemiluminescence reagent of chromogenic substrate.
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