Which term describes the immune system's rapid, non-specific response present at birth?

• A. Adaptive immunity
• B. Innate immunity
• C. Passive immunity
• D. Humoral immunity

Answer: (B)

Innate immunity is the immune system's rapid, non-specific defense that is present from birth. It kicks in immediately when a pathogen is encountered and does not depend on prior exposure or specific antibodies. It includes physical barriers like skin and mucous membranes, chemical barriers such as stomach acid, and cellular defenders like neutrophils and macrophages that engulf invaders, natural killer cells that target infected cells, and the complement system that helps destroy pathogens. This contrasts with adaptive immunity, which is specific to particular pathogens and develops after exposure, with memory that improves responses on subsequent encounters. Passive immunity involves antibodies transferred from another source, providing temporary protection but not produced by the host. Humoral immunity is the antibody-mediated part of adaptive immunity. So, the description fits innate immunity.