All of the following are a pa of the innate immunity except –
**Core Concept**
Innate immunity is the first line of defense against infection, consisting of physical barriers, cellular responses, and humoral factors. It provides immediate, non-specific protection against pathogens, and is essential for preventing infections.
**Why the Correct Answer is Right**
Innate immunity involves cellular responses, such as phagocytosis by neutrophils and macrophages, and the activation of complement system, which helps to eliminate pathogens. The innate immune response also involves the production of cytokines, such as interferons and tumor necrosis factor-alpha, which help to coordinate the immune response. The complement system is a group of proteins that work together to help clear pathogens from the body.
**Why Each Wrong Option is Incorrect**
**Option A:** Complement system is a part of the innate immunity.
**Option B:** Interferons are a type of cytokine that play a role in the innate immune response, helping to protect against viral infections.
**Option C:** Natural killer cells are a type of lymphocyte that are part of the innate immune response, helping to eliminate infected cells or tumor cells.
**Clinical Pearl / High-Yield Fact**
Innate immunity provides immediate protection against infections, but it is not specific to individual pathogens, and can be overwhelmed by large or virulent infections.
**Correct Answer: D**