Which innate defense involves elevation of body temperature as a response to infection?

• A. In inflammation
• B. Complement
• C. Phagocytes
• D. Fever

Answer: (D)

Fever is the systemic innate defense that raises body temperature in response to infection. Pyrogens released by pathogens or immune cells signal the hypothalamus to raise the body’s set point. To reach this new set point, the body generates heat (shivering) and conserves heat (vasoconstriction), producing a higher temperature. This helps slow microbial growth and can enhance certain immune functions, making fever a classic systemic defense against infection. Inflammation is a local response with redness, heat, swelling, and pain at a site; the complement system and phagocytes are other components of innate immunity that don’t by themselves describe a temperature rise.