Antigen antibody interaction

Kalu ram sharmaM.Sc(biotechnology)

Manipal university jaipur

Antigen

• In immunology, an antigen is a molecule capable of inducing an immune response on the part of the host organism.

Antibody

• An antibody (Ab), also known as an immunoglobulin (lg), is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to neutralize pathogens such as bacteria and viruses.

Antibody

Antigen-antibody interaction

• The antigen-antibody interaction is a bimolecular association similar to an enzyme-substrate interaction, with an important distinction.

Antigen-antibody interaction

• Ag-Ab interaction is a specific chemical interaction between antibodies produced by B cells of the white blood cells and antigens during immune reaction.

• In the fundamental reaction in the body by which the body is protected from complex foreign molecules, such as pathogens and their chemical toxin.

Strength of Ag-Ab interaction

• The non-covalent interactions that form the basis of Ag-Ab binding include hydrogen bonds, hydrophobic interactions, and van der Walls interaction.

• Because these interactions are individually weak (compared with a covalent bond), a large number of such interactions are required to form a strong Ag-Ab interaction.

Visualizing concepts

• The interaction between an Ab and an Ag depends on four types of noncovalent forces:

• (1) hydrogen bond:- in which a hydrogen atom is shared between two electronegative atoms.

• (2) ionic bonds:- Between oppositely charged residues.

• (3) Hydrophobic interaction:- in which water forces hydrophobic groups together.

• (4) van der Walls interaction:- Between the outer electron clouds of two or more atoms.

Immunologic tests

• (1)Radioimmunoassay (RIA)• (2)ELISA• (3)Western Blot• (4)Immunoprecipitation• (5)Immunoflurescence

(1)Radioimmunoassay (RIA)

• It is very sensitive in vitro assay technique used to measure concentration of antigen (for example , hormone levels in blood) by use of antibodies.

(2)ELISA(Enzyme-Linked Immunosorbent Assay)

ELISA is test that uses antibodies and color change to identify a substance.

The ELISA has been used as a diagnostic tool in medicine and plant pathology , as well as a quality-control check in various industries.

• The following steps of ELISA:-

• (a)indirect ELISA• (b)sandwich ELISA• (c)competitive ELISA

ELISHA

(3)Western Blot

• The western blot sometimes called the protein immunoblot.

• Used to identification of specific proteins in mixtures.

• Proteins are separated on SDS-PAGE.• Proteins then transferred to membrane.

(4)Immunoprecipitation

• Provides a quick and sensitive test for finding proteins.

• Binds Ab to synthetic bead support centrifuged.

(5)Immunoflurescence

• Provides a quick method for the identification of pathogens and lymphocytes.

• There are currently 2 methods employed:- (a)Direct staining (b)Indirect staining

Application

• Antigen-antibody interaction is used in laboratory techniques for serological test blood compatibility and various pathogenic infection.

• The most basic is ABO blood group determination , which is useful for blood transfusion.

References

• Kuby book• www.google.wikipedia.com

•Thank you