Innate immunity active against viral cells –
## Core Concept
Innate immunity provides the first line of defense against infections and is non-specific, meaning it does not recognize specific pathogens but rather broad categories of them. It includes barriers like the skin and mucous membranes, cellular responses, and protein-based defenses such as complement system and interferons.
## Why the Correct Answer is Right
The correct answer, Interferons (IFNs), are crucial in innate immunity, especially against viral infections. **Interferons** are proteins that are part of the body's non-specific defense mechanisms. They are produced by host cells in response to the presence of viruses and other pathogens. Once released, interferons can induce cells to produce antiviral proteins, which help to create an environment that is not conducive to viral replication. This mechanism is vital for controlling viral infections before the adaptive immune response kicks in.
## Why Each Wrong Option is Incorrect
- **Option A:** While certain cells like neutrophils and macrophages are part of innate immunity and can be involved in responses to viral infections, they are not the most directly active against viral cells in the context provided.
- **Option B:** Complement system can help lyse viral particles or mark them for destruction but is not the most specific or direct innate immune response against viral cells.
- **Option D:** While cytokines are involved in the immune response, including the innate response to viruses, the term is broader than interferons and does not specifically denote the direct action against viral cells as effectively as interferons do.
## Clinical Pearl / High-Yield Fact
A key point to remember is that **interferons** are critical in the innate immune response to viral infections. They have antiviral properties and can induce a state of resistance to viral infection in cells. This is a high-yield fact because understanding the role of interferons can help in grasping how the body initially combats viral infections.
## Correct Answer Line
**Correct Answer: C. Interferons.**