Examples of type 1 hypersensitivity is –
**Core Concept**
Type 1 hypersensitivity reactions are immediate allergic reactions that involve the release of histamine and other chemical mediators from mast cells and basophils. This reaction is mediated by IgE antibodies, which bind to the surface of these cells and trigger the release of histamine and other substances that cause the symptoms of an allergic reaction.
**Why the Correct Answer is Right**
The correct answer involves the release of histamine from mast cells and basophils, which is a key feature of type 1 hypersensitivity reactions. This release of histamine leads to increased vascular permeability, smooth muscle contraction, and mucus production, resulting in symptoms such as hives, itching, swelling, and difficulty breathing. The binding of IgE antibodies to mast cells and basophils is the initial step in this process, which is facilitated by the high-affinity IgE receptor (FcεRI) on these cells.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because type 1 hypersensitivity reactions involve IgE antibodies, not IgG or IgM antibodies.
* IgG and IgM antibodies are involved in type 2 and type 3 hypersensitivity reactions, respectively.
**Option B:** This option is incorrect because anaphylaxis is a classic example of a type 1 hypersensitivity reaction, but it's not the only one. Other examples include allergic rhinitis and atopic dermatitis.
* Anaphylaxis is a severe, life-threatening type 1 hypersensitivity reaction that requires immediate medical attention.
**Option C:** This option is incorrect because type 4 hypersensitivity reactions are cell-mediated and involve T lymphocytes, not IgE antibodies or mast cells.
* Type 4 hypersensitivity reactions are characterized by a delayed response, often occurring 48-72 hours after exposure to the allergen.
**Option D:** This option is incorrect because type 3 hypersensitivity reactions involve immune complexes, not IgE antibodies or mast cells.
* Type 3 hypersensitivity reactions are characterized by the formation of immune complexes that deposit in tissues and cause inflammation.
**Clinical Pearl / High-Yield Fact**
Remember that type 1 hypersensitivity reactions are mediated by IgE antibodies and involve the release of histamine from mast cells and basophils. This can lead to a range of symptoms, from mild hives and itching to life-threatening anaphylaxis.
**Correct Answer:** C. Anaphylaxis, allergic rhinitis, atopic dermatitis.