The host's ability to limit pathogen burden and includes such defenses as physical barriers (e.g., skin) and a rapid immune response is called _____.

• A. Host Resistance
• B. Humoral Immunity
• C. Cellular Immunity
• D. Innate Immunity

Answer: (A)

Innate immunity is the body's first line of defense, providing immediate, non-specific protection that helps limit pathogen burden. Physical barriers like the skin block entry, while the rapid response involves non-specific mechanisms such as inflammation, phagocytes (like neutrophils and macrophages), natural killer cells, and the complement system. This contrasts with humoral immunity (antibody-mediated, part of the adaptive response) and cellular immunity (T-cell–mediated, also adaptive), which are targeted and take longer to develop after exposure. It’s also true that host resistance describes the overall ability to fight infection and can include both innate and adaptive elements, but the features described—physical barriers and a rapid response—are hallmarks of innate immunity.