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How does innate immunity differ from acquired immunity?

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The human body defends itself against infection through two primary, distinct systems: innate immunity and acquired immunity.1

Innate Immunity

Innate immunity consists of defense mechanisms present at birth that provide immediate, nonspecific protection against a broad range of pathogens. These include physical barriers like the skin, chemical barriers such as enzymes in saliva, and cellular responses involving phagocytes and natural killer cells. While these responses occur rapidly, they do not provide lasting immunity to specific pathogens.12

Acquired Immunity

Acquired immunity develops following exposure to a specific infectious agent or through vaccination. It is characterized by the precise recognition of antigens by B cells and T cells. This system is highly targeted; for instance, B cells produce antibodies tailored to specific invaders. A key feature of this system is immunological memory, where memory cells enable the body to respond more rapidly and effectively upon subsequent encounters with the same pathogen, often providing long-term protection.134