Final answer:
Yes, mast cells mediate allergic reactions in local tissues by releasing histamine and other mediators in response to allergens, causing symptoms like itching and swelling.
Step-by-step explanation:
The statement 'Mast cells mediate allergic reactions in local tissues' is true. Mast cells are found within connective tissues and are key players in immune responses, particularly allergic reactions.
They contain granules rich in histamine and heparin, and upon activation, for instance by an allergen, they degranulate, releasing these mediators. This degranulation process is crucial in mounting an allergic response by causing symptoms such as vasodilation, increased blood flow, itching, swelling, and redness. In cases of re-exposure to the allergen, mast cells that are primed with IgE antibodies specific to that allergen release chemical mediators, including histamine, which leads to the inflammation and symptoms associated with allergies.