True or false? most antigens are large, complex molecules that are not normally present in the body.

a. True

b. False

The answer is true.

Antigens are molecules capable to induce an immune response, "targeted" by antibodies. Antigens are usually proteins, peptides, or polysaccharides but they can combine with lipids and nucleic acids and form more complex antigens (lipopolysaccharide). Usually, antigens are exogenous (foreign substances), but sometimes are part of the host itself (in an autoimmune disease). All of them contain an epitope which is a part of an antigen that can be recognized and bound by an antibody.