Which of the following is NOT a component of the innate immune system?

• A. Skin
• B. Phagocyte
• C. Antibody
• D. Complement system

Answer: (C)

Antibodies are produced by B cells as part of the adaptive immune response, not the innate arm. The innate system provides immediate, non-specific defense and includes physical barriers like skin, phagocytes that directly ingest pathogens, and the complement system that enhances inflammation and pathogen destruction. Antibodies, by contrast, are highly specific proteins that recognize particular antigens and are generated after exposure to a pathogen (or vaccination), with the ability to create immunological memory. Because antibodies belong to adaptive immunity rather than innate, they are not a component of the innate immune system.