Antigens

Antigens:-

Definition:- Antigens are substances which, when introduced into the body, stimulate the production of antibodies.

Chemical Nature:- The antigens are mostly the conjugated proteins like lipoproteins, glycoproteins and nucleoproteins.

Structure:- 

> Antigenic determinants or epitopes (Gk. epi – upon, topos- place) are components of antigen. 

> Each antigen carries many epitopes. 

> Each Y-shaped antibody mol­ecule has atleast two binding sites that can attach to a specific epitope on an antigen. 

> An antibody can also bind to identical epitopes of two different cells at the same time which can cause neighbouring cells to aggregate. 

> Antigens combine with the antibody. 

> The combination is very much like the lock and key analogy.