Antigens and Antigenic Determinants

Epitope:-is the unique region on an Ag that will bind a complementary Ab i.e. that portion of an antigen that combines with the products of a specific immune response. It is also called antigenic determinant. Epitopes generally are significantly smaller than the antigens which contain them (and much smaller than the size of an antibody).A single antigen often contains numerous Epitopes. Antigenic determinants react with Abs in a lock and key fashion based on structural complementarity. Forces characteristic of Ag-Ab binding include Van Der Waal-London dipole interactions, hydrophobic interaction and ionic Columbic bonding, these cooperate together between the Epitopes of the Ags and the variable Fab regions of the Abs to form immune complex. The other [portion of the Ag other than the Epitope are termed immunogenic carrier.