Which of the following white blood cells act as scavengers when they engulf and digest pathogens?
**Core Concept**
Macrophages play a crucial role in the innate immune response by acting as scavengers that engulf and digest pathogens, thereby helping to protect the body from infection. This process is known as phagocytosis, where the macrophage engulfs the pathogen and then digests it using enzymes and acidic lysosomes.
**Why the Correct Answer is Right**
Macrophages are a type of white blood cell that are specialized to recognize and engulf pathogens, including bacteria, viruses, and fungi. They use receptors such as complement receptor 3 (CR3) and mannose receptor to recognize and bind to pathogens, which then triggers the process of phagocytosis. Once the pathogen is engulfed, the macrophage uses enzymes such as lysozyme and proteases to break it down, and then fuses with lysosomes to deliver acidic digestive enzymes that further digest the pathogen.
**Why Each Wrong Option is Incorrect**
* **Option A:** Neutrophils are a type of white blood cell that are also involved in phagocytosis, but they are primarily responsible for acute inflammation and are not as effective at engulfing and digesting pathogens as macrophages.
* **Option B:** Lymphocytes are a type of white blood cell that are primarily involved in the adaptive immune response, and are not responsible for phagocytosis.
* **Option D:** Eosinophils are a type of white blood cell that are involved in fighting parasites and in allergic reactions, but are not responsible for phagocytosis.
**Clinical Pearl / High-Yield Fact**
Macrophages are not only important for engulfing and digesting pathogens, but also play a role in presenting antigens to T-cells, thereby activating the adaptive immune response.
**Correct Answer:** C. Macrophages are the white blood cells that act as scavengers when they engulf and digest pathogens.