Final answer:
Mast cells are the primary cells that release chemical mediators in the immediate phase of a type I hypersensitivity reaction. Late-phase reactions involve other immune cells like eosinophils, neutrophils, and lymphocytes which are recruited by factors from mast cells.
Step-by-step explanation:
Cells Involved in Type I Hypersensitivity Reactions
The cells that are responsible for releasing the chemical mediators of inflammation in the immediate phase of a type I hypersensitivity reaction are mast cells. Upon a second exposure to an allergen, IgE-primed mast cells bind to the antigen and release various chemical mediators, such as histamine and cytokines. These substances lead to the symptoms associated with allergic reactions, like swelling, redness, and itching.
It is important to differentiate between the immediate and late-phase reactions in this type of hypersensitivity. Late-phase reactions may develop 4-12 hours after the early phase and involve other immune cells such as eosinophils, neutrophils, and lymphocytes. These cells are drawn to the site of reaction by chemotactic factors released from mast cells during the immediate phase.