Which of the following answers is an inflammatory mediator that stimulates vasodilation allowing immune cells to enter the site of infection?

• A. Collagen.
• B. Serotonin.
• C. C3b protein.
• D. Histamine.

Answer: (D)

Verified step by step guidance

1. Understand the role of inflammatory mediators: Inflammatory mediators are substances released by immune cells that help to initiate and regulate the inflammatory response. They play a crucial role in the body's defense mechanism against infections and injuries.
2. Identify the function of vasodilation: Vasodilation is the widening of blood vessels, which increases blood flow to the affected area. This process allows immune cells to reach the site of infection more efficiently.
3. Learn about histamine: Histamine is a well-known inflammatory mediator that is released by mast cells and basophils during an immune response. It is primarily responsible for causing vasodilation and increasing the permeability of blood vessels.
4. Differentiate between the options: Collagen is a structural protein, not an inflammatory mediator. Serotonin is a neurotransmitter that can have various roles, including vasoconstriction, but is not primarily known for vasodilation in inflammation. C3b protein is part of the complement system and aids in opsonization, not vasodilation.
5. Conclude with the correct answer: Based on the understanding of the roles of these substances, histamine is the correct answer as it is the inflammatory mediator that stimulates vasodilation, allowing immune cells to enter the site of infection.