General Features of Antigen-antibody Reactions

Antigen-Antibody reactions have the following general characteristics:

1. The reaction is specific. An antigen combines only with its homolo-gous antibody and vice versa. The specificity, however is not ab-solute and cross reaction may occur due to antigenic similarity and relatedness.

2. Entire molecules react and not fragments.

3. There is no denaturation of the antigen or the antibody during the reaction.

4. The combination occurs at the surface.

5. The combination is firm but reversible. The firmness of the union is influenced by the Affinity and the Avidity of the reaction. Affinity refers to the intensity if interaction between the Antigen and Anti-body. Avidity is the strength of the bond after the formation of the complexes.

6. Both antigens and antibodies participate in the formation of agglu-tinates or precipitates.

7. Antigens and Antibodies can combine in varying proportion