What substance responds to injury infection or allergy by producing and releasing substances including heparin histamine?

The substance that responds to injury, infection, or allergy by producing and releasing substances including heparin, histamine, and serotonin is known as *mast cells*. These cells are a type of white blood cell found in connective tissues throughout the body. When activated, mast cells degranulate, releasing their pre-formed mediators, which include heparin, histamine, serotonin, and other inflammatory substances. These mediators play important roles in the body's immune response and in the development of allergic reactions.