Which of the following statements about pyrogens is correct?

• A. Pyrogens are substances that induce fever by acting on the hypothalamus.
• B. Pyrogens suppress the inflammatory response.
• C. Pyrogens are exclusively produced by viruses.
• D. Pyrogens are only found in adaptive immunity.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the definition of pyrogens. Pyrogens are substances that cause fever by affecting the body's temperature regulation center, which is the hypothalamus in the brain.
2. Step 2: Recognize that pyrogens can be either exogenous (originating outside the body, such as bacterial toxins) or endogenous (produced by the body, such as certain cytokines released during immune responses).
3. Step 3: Analyze the options given: Pyrogens induce fever, so the statement that they suppress the inflammatory response is incorrect because fever is part of the inflammatory process.
4. Step 4: Consider the source of pyrogens: they are not exclusively produced by viruses; bacteria and other microorganisms can also produce pyrogens, as well as the body's own immune cells.
5. Step 5: Understand that pyrogens are involved in innate immunity and the general immune response, not only in adaptive immunity, so the statement limiting them to adaptive immunity is incorrect.