A scientist working in the laboratory on the mechanisms involved in inflammation. He observes that the leucocytes leave the blood vessels and move towards the site of bacteria. Which of the following is likely to mediate this movement of the bacteria?
**Core Concept**
The movement of leucocytes from the blood vessels towards the site of inflammation is a critical step in the innate immune response, involving the chemotaxis of white blood cells. This process is mediated by chemical signals that attract leucocytes to the site of infection or injury.
**Why the Correct Answer is Right**
The correct answer is chemokines. Chemokines are a family of small cytokines that are produced in response to inflammation, injury, or infection. They bind to specific receptors on the surface of leucocytes, triggering a signaling cascade that leads to the activation and migration of these cells towards the site of inflammation. Chemokines, such as CXCL8 (IL-8), are produced by various cell types, including endothelial cells, macrophages, and epithelial cells, and play a crucial role in directing the trafficking of leucocytes to the site of infection.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is too vague. While it is true that adhesion molecules play a role in the migration of leucocytes, they are not the primary mediators of the movement of leucocytes towards the site of inflammation.
**Option B:** This option is incorrect because it refers to the process of phagocytosis, which is the engulfment and ingestion of foreign particles or microorganisms by leucocytes. While phagocytosis is an important function of leucocytes, it is not directly related to the movement of leucocytes towards the site of inflammation.
**Option C:** This option is incorrect because it refers to the process of diapedesis, which is the migration of leucocytes through the endothelial lining of blood vessels. While diapedesis is an important step in the migration of leucocytes, it is not the primary mediator of the movement of leucocytes towards the site of inflammation.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that chemokines play a critical role in directing the trafficking of leucocytes to the site of infection. Understanding the chemokine receptors and their ligands is crucial for developing effective therapies for inflammatory diseases.
**Correct Answer:** C. Chemokines