Which cytokine is primarily responsible for driving inflammatory responses and fever during infection?

• A. IL-1
• B. IL-4
• C. IL-10
• D. IL-2

Answer: (A)

Cytokines from activated innate immune cells set the stage for inflammation and fever, and IL-1 is a key driver of both. IL-1, produced by macrophages in response to infection, acts on the hypothalamus to raise the body's temperature (the endogenous pyrogen mechanism) through prostaglandin E2. It also promotes inflammation by upregulating adhesion molecules on endothelium to recruit leukocytes and by stimulating the production of other mediators like IL-6, amplifying the acute-phase response. In contrast, the other cytokines have different primary roles: IL-4 promotes Th2 responses and B cell class switching, IL-10 dampens inflammation, and IL-2 drives T cell proliferation.