Which statement best describes innate immunity?

• A. Adaptive Immunity
• B. Innate Immunity
• C. Passive Immunity
• D. Active Immunity

Answer: (B)

Innate immunity is the body's immediate, non-specific defense that acts without prior exposure to an pathogen. It uses broad defenses—physical barriers like skin and mucous membranes, chemical barriers, and cellular players such as neutrophils, macrophages, dendritic cells, natural killer cells, and the complement system—to recognize common features of many microbes. This response is rapid and nonspecific, meaning it doesn’t tailor itself to a particular organism and does not create lasting memory after an encounter.

In contrast, adaptive immunity is specific to particular antigens and builds memory over time through T and B lymphocytes, providing targeted and increasingly rapid responses upon re-exposure. Passive immunity involves receiving antibodies from another source (for example, maternal antibodies or a therapeutic antibody) and does not involve the host’s own immune activation. Active immunity refers to the host generating its own immune response to a pathogen or vaccine, leading to memory and longer-lasting protection.