What is the second level of defense?

The second level of defense typically refers to the body's immune response, specifically the innate immune system, which acts after the first line of defense (physical barriers like skin and mucous membranes) is breached. This level includes various immune cells, such as phagocytes and natural killer cells, that respond quickly to pathogens. It also involves inflammatory responses and the release of antimicrobial substances to help control infections. Overall, the second level of defense plays a crucial role in providing a rapid and non-specific response to invading microorganisms.