Final answer:
Proteins are the most immunogenic chemical family among antigens due to their complex structures, which stimulate both humoral and cellular immune defenses. Option E.
Step-by-step explanation:
An antigen is a foreign or "non-self" macromolecule that interacts with the immune system. Among the different classes of antigens, which include carbohydrates, lipids, nucleic acids, and combinations of these molecules, proteins are known to be the most immunogenic chemical family.
Proteins often stimulate both humoral (antibody-mediated) and cellular immune defenses due to their complex three-dimensional structures. This complexity allows proteins to present multiple epitopes that can be recognized by the immune cells, making proteins highly effective as antigens.
In contrast, carbohydrates, which are less complex, typically only stimulate humoral immune responses, while lipids and nucleic acids are generally the least antigenic unless they form part of larger complex molecules like glycolipids or nucleoproteins. So option E.