write about reaction of antigen and antibodies.
The antibody becomes attached to the antigen in a lock-and-key fashion, forming an antigen-antibody complex. Antibodies are a type of protein molecule known as immunoglobulins. Antibodies are Y-shaped molecules. On the antibody there are present unique antigenic determinant which binds to a site on the antigen, leading to the destruction of the antigen in several ways. This process of sticking together of antibody with antigen is known as agglutination.