Which are the body's three main defenses against infection?

• A. Normal floras, body system defenses, and inflammation.
• B. Antibodies, vaccines, and memory cells
• C. Skin only
• D. Coughing only

Answer: (A)

Protection against infection happens in layers that work together. The normal flora living on and in us helps prevent invaders by occupying niches and producing substances that hinder pathogens. The body’s general defenses—physical and chemical barriers like skin and mucous membranes, secretions, and cellular responses such as phagocytes and fever—provide rapid, nonspecific protection. Inflammation then acts as the local, coordinated response to injury or infection, bringing immune cells to the site, increasing blood flow, and promoting healing. Taken together, these elements—normal flora, the body’s broad defense systems, and the inflammatory response—form the main, immediate protections against infection.

Antibodies, vaccines, and memory cells belong to the adaptive immune system and develop after exposure or vaccination, offering targeted, long-term protection rather than the immediate, nonspecific barriers described above. A single aspect like skin or coughing represents parts of the defense, but not the full, layered set.