AIIMS PG Exam – 84905

Assertion: Anaphylactoid reaction can be caused by first exposure.

Reason: Involves mast cell degranulation but not IgE.

A. Assertion and reason are correct and correlate

B. Assertion and reason are incorrect and do not correlate

C. Assertion is correct but reason is incorrect

D. Assertion is incorrect but reason is correct

Show Answer

[ads id=”53026″]

Correct Answer » C Explanation

Ans: C. Assertion is correct but reason is incorrect
 Anaphylaxis is a severe allergic reaction of rapid onset affecting many-body systems. It is due to the release of inflammatory mediators and cytokines from mast cells and basophils, typically due to an immunologic reaction but sometimes non-immunologic mechanism.
 In the immunologic mechanism, immunoglobulin E (IgE) binds to the antigen (the foreign material that provokes the allergic reaction). Antigen-bound IgE then activates FcεRI receptors on mast cells and basophils. This leads to the release of inflammatory mediators such as histamine. These mediators subsequently increase the contraction of bronchial smooth muscles, trigger vasodilation, increase the leakage of fluid from blood vessels, and cause heart muscle depression. There is also an immunologic mechanism that does not rely on IgE, but it is not known if this occurs in humans.