Not true about innate immunity
**Core Concept**
Innate immunity refers to the non-specific defense mechanisms that provide immediate defense against infection and injury. It includes physical barriers, cells, and proteins that recognize and respond to pathogens in a non-specific manner.
**Why the Correct Answer is Right**
Innate immunity is the first line of defense against infection and is mediated by cells such as neutrophils, macrophages, and natural killer cells. These cells recognize pathogens through pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) and NOD-like receptors (NLRs). The correct answer is a statement that accurately describes a characteristic of innate immunity.
**Why Each Wrong Option is Incorrect**
**Option A:** Innate immunity is specific to certain pathogens.
* This is incorrect because innate immunity is non-specific, meaning it does not recognize specific pathogens but rather recognizes common pathogen-associated molecular patterns (PAMPs).
**Option B:** Innate immunity only involves physical barriers.
* This is incorrect because innate immunity involves not only physical barriers (such as the skin and mucous membranes) but also cells and proteins that recognize and respond to pathogens.
**Option C:** Innate immunity is mediated by B cells and T cells.
* This is incorrect because innate immunity is mediated by cells such as neutrophils, macrophages, and natural killer cells, not B cells and T cells, which are part of the adaptive immune response.
**Option D:** Innate immunity provides long-term immunity against infections.
* This is incorrect because innate immunity provides immediate but non-specific defense against infection, not long-term immunity.
**Clinical Pearl / High-Yield Fact**
Innate immunity is often referred to as the "first line of defense" because it provides immediate protection against infection and injury. Understanding the mechanisms of innate immunity is crucial for recognizing and treating infections.
**Correct Answer: A. Innate immunity is specific to certain pathogens.**