Which of the following best characterizes the innate immune defenses?

• A. They are only effective against viral infections.
• B. They provide a rapid, non-specific response to pathogens.
• C. They generate highly specific antibodies against antigens.
• D. They require prior exposure to pathogens for activation.

Answer: (B)

Verified step by step guidance

1. Understand the definition of innate immune defenses: these are the body's first line of defense against pathogens and act immediately or within hours of an antigen's appearance in the body.
2. Recognize that innate immunity is non-specific, meaning it does not target specific pathogens but rather responds to a broad range of invaders.
3. Note that innate immune defenses include physical barriers (like skin), chemical barriers (such as stomach acid), and cellular defenses (like phagocytic cells).
4. Contrast innate immunity with adaptive immunity, which is specific, slower to respond, and requires prior exposure to a pathogen to generate a targeted response.
5. Conclude that the best characterization of innate immune defenses is that they provide a rapid, non-specific response to pathogens, without the need for prior exposure.