What substance is released by cells of the immune system to increase blood supply during inflammation?

Histamine is a chemical messenger released by mast cells and basophils in response to inflammatory stimuli. Its primary role in inflammation is to increase blood flow to the affected area, which is essential for the recruitment of immune cells and other inflammatory mediators to sites of injury or infection. Histamine achieves this by causing dilation of blood vessels (vasodilation) and increasing their permeability. This ensures that more blood reaches the damaged tissue, allowing for an enhanced immune response and facilitating healing.

While cytokines, prostaglandins, and interferons also play important roles in the immune response, they have different functions. Cytokines are signaling proteins that mediate and regulate immunity, inflammation, and hematopoiesis; prostaglandins are lipid compounds that contribute to inflammation and pain but do not primarily function to increase blood supply; and interferons are primarily involved in the defense against viral infections and have roles in immune regulation. Thus, histamine's specific role in promoting increased blood supply distinctly marks it as the correct answer in the context of inflammation.