Which characteristic is true of monoclonal antibodies?

Monoclonal antibodies are indeed characterized by their ability to target one specific protein antigen. This specificity arises because monoclonal antibodies are derived from a single clone of B cells, meaning they originate from the same type of cell. As a result, they recognize and bind to the same epitope on their target antigen, leading to very precise therapeutic or diagnostic applications.

For instance, this characteristic is especially important in medical treatments, where the precise targeting of a specific antigen can enhance the effectiveness of therapies against diseases such as cancer or autoimmune disorders. The ability to focus on a single target allows for less off-target effects, making monoclonal antibodies an important tool in targeted therapies.

In contrast, the other statements do not describe monoclonal antibodies accurately. They are not produced from multiple sources, do not evolve in response to treatment as they are designed to be stable entities, and they can indeed be effective against tumors by targeting tumor-associated antigens.