Final answer:
Mast cells are immune cells found in connective tissue that release histamine to contribute to inflammatory and allergic responses.
Step-by-step explanation:
Mast cells are a type of immune cell that can be found in connective tissue. They contain cytoplasmic granules that store histamine and heparin. When these cells are irritated or damaged, they release histamine, which then contributes to the body's inflammatory response by causing vasodilation, increased blood flow, itching, swelling, and redness—symptoms commonly associated with allergic reactions. Additionally, mast cells play a role in defending against parasites and are involved in hypersensitivity responses, such as allergies. These cells originate from hematopoietic stem cells, similar to other blood cells, and hold a vital role in the immune system.