What are the two categories of defense responses in the immune system?

• A. Humoral immunity and cell-mediated immunity
• B. Innate immune response and adaptive immune response
• C. Physical barriers and chemical barriers
• D. Inflammatory response and fever response

Answer: (B)

The two broad categories of defense responses are innate immunity and adaptive immunity. Innate immunity provides quick, nonspecific defenses that act right away, using barriers like skin and mucous membranes, as well as cells such as phagocytes and natural killer cells, and processes like inflammation. Adaptive immunity is slower at first but highly specific to the particular pathogen and builds memory, involving B cells that produce antibodies (humoral response) and T cells that attack infected cells or help other immune cells (cell-mediated response). Together, innate defenses contain threats early, while adaptive defenses target specific invaders and improve with repeated exposure. The other options describe parts of these systems—either components within innate or within adaptive—rather than the two overarching categories.