Which one of the following does NOT present antigens?
**Core Concept**
The question is testing the understanding of the role of different cells in antigen presentation, a crucial aspect of the immune response. Antigen presentation is the process by which cells display pieces of foreign substances (antigens) on their surface, allowing T-cells to recognize and respond to them.
**Why the Correct Answer is Right**
The correct answer is **C. Eosinophils**. Eosinophils are a type of white blood cell involved in fighting parasites and in allergic reactions. They do not present antigens to T-cells, unlike dendritic cells, macrophages, and B-cells, which are professional antigen-presenting cells (APCs). This is because eosinophils do not express major histocompatibility complex (MHC) class II molecules on their surface, which are necessary for antigen presentation.
**Why Each Wrong Option is Incorrect**
* **Option A: Dendritic cells** - These cells are professional APCs that play a key role in initiating the immune response by presenting antigens to T-cells.
* **Option B: Macrophages** - Like dendritic cells, macrophages are professional APCs that engulf foreign particles, process them, and present antigens to T-cells.
* **Option D: B-cells** - B-cells, or B-lymphocytes, are also professional APCs that present antigens to T-cells and activate the immune response.
**Clinical Pearl / High-Yield Fact**
Dendritic cells, macrophages, and B-cells are all professional antigen-presenting cells that play a crucial role in initiating the immune response. Understanding the differences between these cells is essential for developing effective immunotherapies and vaccines.
**Correct Answer:** C. Eosinophils