Question

How does fever indicate that your body's immune system is doing its job?
Fever increases red blood cell production.
Fever raises the body's temperature to destroy harmful substances.
Fever triggers inflammation.
Fever causes the secretion of hormones that fight harmful substances.

Answer 1

Correct answer: "Fever raises the body's temperature to destroy harmful substances."

Why: Fever is produced when immune cells release pyrogenic cytokines (IL‑1, IL‑6, TNF, interferons) that act on the hypothalamus (via prostaglandin E2) to raise the body's temperature set point. The higher temperature can slow growth of some pathogens and enhances several immune functions (e.g., phagocytosis, lymphocyte activity), so a fever is a sign the immune system is active.

Why the others are wrong:
- Fever does not primarily increase red blood cell production.
- Fever is a component/result of the inflammatory response driven by cytokines, not something that independently triggers inflammation.
- Fever itself does not directly cause secretion of special “hormones that fight harmful substances”; immune cytokines drive the response.