Prausnitz kustner reaction is which type of hypersensitivity –
**Core Concept**
The Prausnitz-Kustner (PK) reaction is a classic example of an immediate hypersensitivity reaction, specifically a type of anaphylactic reaction. It involves the transfer of IgE antibodies from an allergic individual to a naive recipient, leading to the release of histamine and other mediators from mast cells.
**Why the Correct Answer is Right**
The PK reaction demonstrates the role of IgE antibodies in mediating allergic reactions. When IgE antibodies from an allergic individual bind to mast cells in a naive recipient, they trigger the release of histamine and other mediators, resulting in symptoms such as urticaria, angioedema, and bronchospasm. This reaction is a key mechanism underlying anaphylaxis and atopic diseases like asthma and eczema.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the PK reaction is not a delayed hypersensitivity reaction, which involves T-cell mediated immunity and typically takes 48-72 hours to develop.
**Option B:** This option is incorrect because the PK reaction is not a type of graft-versus-host disease, which occurs when immune cells from a donor react against the recipient's tissues.
**Option C:** This option is incorrect because the PK reaction is not a type of autoimmune reaction, which involves the immune system attacking the body's own tissues.
**Clinical Pearl / High-Yield Fact**
The PK reaction is a classic example of the transfer of immunity from one individual to another, highlighting the importance of IgE antibodies in mediating allergic reactions.
**Correct Answer: C. Type I hypersensitivity. Immediate hypersensitivity reaction.