Final answer:
It is (Option b) false that each antigen has a single specific epitope; antigens can have multiple epitopes that are recognized by different antibodies, and cross reactivity can occur when antibodies bind to similar epitopes on different antigens.
Step-by-step explanation:
The statement that each antigen has a single specific epitope is false. Antigens are complex molecules that can display multiple epitopes. An epitope is a small, specific part of an antigen that is recognized and bound by an antibody. It is possible for multiple antibodies to bind to different epitopes on the same antigen, and this specificity is due to the unique genetic encoding of each antibody which allows for the possibility of various antigen binding properties.
Moreover, an epitope typically covers an area about the size of four to six amino acids on the surface of an antigen, allowing for the possibility of cross reactivity. Cross reactivity occurs when an antibody does not only bind to the antigen that induced its production but also to different antigens that present the same or similar epitopes. Additionally, T cells can recognize and interact with multiple antigenic determinants on the same antigen, further demonstrating the diversity of epitopes on a single antigen molecule.