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An illustration that shows how antigens induce the immune system response by interacting with an antibody that matches the molecular structure of an antigen. In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. [1]
In contrast, the B cell antigen-specific receptor is an antibody molecule on the B cell surface and recognizes native (unprocessed) antigen without any need for antigen processing. Such antigens may be large molecules found on the surfaces of pathogens, but can also be small haptens (such as penicillin) attached to carrier molecule. [60]
Each antibody binds to a specific antigen in a highly specific interaction analogous to a lock and key.. An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that cause disease.
In immunology, a paratope, also known as an antigen-binding site, is the part of an antibody which recognizes and binds to an antigen. [1] [2] It is a small region at the tip of the antibody's antigen-binding fragment and contains parts of the antibody's heavy and light chains. [1] [2] Each paratope is made up of six complementarity-determining ...
Although epitopes are usually non-self proteins, sequences derived from the host that can be recognized (as in the case of autoimmune diseases) are also epitopes. [1] The epitopes of protein antigens are divided into two categories, conformational epitopes and linear epitopes, based on their structure and interaction with the paratope. [2]
Antigen processing, or the cytosolic pathway, is an immunological process that prepares antigens for presentation to special cells of the immune system called T lymphocytes. It is considered to be a stage of antigen presentation pathways.
These stains use antibodies to bind to specific antigens, usually of protein or glycoprotein origin. Since antibodies are normally invisible, special strategies must be employed to detect these bound antibodies. In an immunoperoxidase procedure, an enzyme known as a peroxidase is used to catalyze a chemical reaction to produce a coloured product.
Class switching is mediated by the enzyme AID (activation-induced cytidine deaminase) and occurs after the B cell binds an antigen through its B cell receptor. Class-switching usually requires interaction with a T helper cell. [3] [4] In humans, there are five heavy chain isotypes α,δ,γ,ε,μ, corresponding to five antibody isotypes: