Question

Following a bee sting, the person develops periorbital edema, laryngospasm, breathing difficulty. These reactions are mediated through which of the following?

• A. Cytotoxic T cell
• B. IgE mediated
• C. IgA mediated
• D. Immune complex reactions

Hint:

Immediate swelling and breathing trouble after a sting is anaphylaxis, a Type I hypersensitivity reaction driven by IgE on mast cells.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The person develops swelling around the eyes, spasm of the voice box and breathing difficulty right after a bee sting. This picture describes an anaphylactic reaction, and we are asked which immune mechanism causes it.

Step 2: Key Concept:
This is a Type I hypersensitivity reaction, which is mediated by IgE antibodies.

Step 3: Detailed Explanation:
On a first exposure to bee venom, the immune system makes IgE antibodies specific to venom proteins, and these IgE molecules attach to receptors on mast cells and basophils, this is called sensitization.
On a repeat sting, the venom antigen binds and cross links the IgE already sitting on the mast cell surface, and this cross linking triggers the mast cell to degranulate within minutes.
The released mediators, mainly histamine along with leukotrienes and prostaglandins, cause blood vessels to leak fluid into tissue, giving periorbital edema, and cause smooth muscle spasm in the airway, giving laryngospasm and breathing difficulty.
This fast, IgE driven, mast cell mediated response is exactly what is seen in anaphylaxis after an insect sting, a drug, or a food allergen.

Step 4: Why the other options are wrong:
Cytotoxic T cell reactions are Type IV, cell mediated, delayed hypersensitivity that takes one to several days to develop, such as in contact dermatitis or graft rejection, which does not fit a reaction within minutes of a sting.
IgA is a mucosal antibody involved in local defense at gut and respiratory surfaces, it is not the antibody class that drives immediate hypersensitivity reactions.
Immune complex reactions are Type III hypersensitivity, where antigen antibody complexes deposit in tissues and activate complement over hours to days, as in serum sickness, not the immediate picture described here.

Step 4: Final Answer:
The reaction is IgE mediated, a Type I hypersensitivity response to bee venom.