Antibody-antigen interaction, mechanism

The specificity of antibody-antigen interactions is a result of a structural fit between the antibody binding site and the antigenic determinant. An understanding of the mechanism of the antigen-antibody interactions has revealed the existence of hypervariable and conserved regions. The... 

Figure 27 Schanatic illustration of a capping/uncapping/release mechanism that utilizes antibody-hapten and antibody-antigen interactions for signaUng. ...

The immune system comprises two main mechanisms innate and acquired immunity. The acquired immunity is the ability of an organism to improve its defenses after being exposed to specific molecules. In this case, specific antibodies are produced and secreted by lymphocytes. Immunoglobulins (antibodies) are Y -shaped proteins of approximately 150kDa composed of four polypeptide chains two heavy and two light chains, linked by disulfide bonds. They present both constant and variable sequences, the latter ones being responsible for specific antibody-antigen interactions. ... 

The process of activation of neutrophils is essentially similar. They are activated, via specific receptors, by interaction with bacteria, binding of chemotactic factors, or antibody-antigen complexes. The resultant rise in intracellular Ca affects many processes in neutrophils, such as assembly of micrombules and the actin-myosin system. These processes are respectively involved in secretion of contents of granules and in motility, which enables neutrophils to seek out the invaders. The activated neutrophils are now ready to destroy the invaders by mechanisms that include production of active derivatives of oxygen. 

The selectivity can be greatly enhanced by using specific antibody-antigen (Ab-Ag) interactions in the transport mechanism. Two main groups, mono- and polyclonal antibodies, can be used for selective liquid membrane pertraction of different compounds. 

In more sophisticated experiments the AFM tip can be used to grab hold of parts of a tethered molecule to see how it responds to being pulled apart. Alternatively, the forces between molecules adsorbed onto the AFM tip and those adsorbed onto the surface can be measured. This has been used, for example, to measure the forces involved in the mechanical unfolding of proteins, antibody-antigen and other protein-protein interactions, or the binding of complementary strands of DNA (Figure 8.2). 

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