The most impoant cells in type I hypersensitivity ?
**Core Concept**
Type I hypersensitivity, also known as immediate hypersensitivity, is a type of allergic reaction that occurs within minutes of exposure to an allergen. This reaction is mediated by IgE antibodies, which trigger the release of histamine and other chemical mediators from mast cells and basophils.
**Why the Correct Answer is Right**
The correct answer involves mast cells and basophils, which are the primary effector cells in type I hypersensitivity reactions. Upon binding of IgE antibodies to their Fc receptors on the surface of these cells, the allergen cross-links the IgE molecules, leading to the activation of the cell and the release of histamine and other chemical mediators. This results in increased vascular permeability, smooth muscle contraction, and mucus production, which are characteristic of type I hypersensitivity reactions.
**Why Each Wrong Option is Incorrect**
**Option A:** Neutrophils are not primarily involved in type I hypersensitivity reactions, as they are more associated with phagocytosis and the elimination of pathogens.
**Option B:** T lymphocytes play a role in the initiation and regulation of the immune response, but they are not the primary effector cells in type I hypersensitivity reactions.
**Option C:** Eosinophils are involved in type II and type III hypersensitivity reactions, and are also associated with parasitic infections, but they are not the primary effector cells in type I hypersensitivity reactions.
**Clinical Pearl / High-Yield Fact**
The mast cell is often referred to as the "effector cell" of type I hypersensitivity reactions, and its activation leads to the release of a multitude of chemical mediators, including histamine, tryptase, and cytokines, which contribute to the symptoms of allergic reactions.
**Correct Answer: C. Mast cells and basophils are the most important cells in type I hypersensitivity reactions.**