The Question is from neet-zoology , and it was created by the author A SUBRAMANYAM

Question

A patient presents with severe allergic symptoms after consuming peanuts.  Which of the following is the LEAST likely mechanism contributing to their reaction?

A SUBRAMANYAM · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Type I hypersensitivity reaction
 **Related Topics**: IgE-mediated response, mast cell degranulation, complement system, antibody isotypes
 **Prerequisites**: Understanding of the immune system, specifically humoral immunity and allergic reactions.
## SOLUTION PATHWAY
**Given Information**:
  A patient experiences severe allergic symptoms after peanut consumption.
  We need to identify the least likely mechanism involved.
**Method & Steps**:
 1. Understand the typical mechanism of a peanut allergy.
  Reasoning:  Peanut allergies are classic examples of Type I hypersensitivity reactions, mediated by IgE antibodies.
 2. Analyze each option's role in a Type I reaction.
  Working:
  A. Mast cell degranulation and histamine release: This is a central feature of Type I hypersensitivity.  IgE bound to mast cells cross-links upon allergen exposure, triggering degranulation and the release of histamine and other inflammatory mediators.
  B. Cross-linking of IgE antibodies: This is the initiating event in a Type I reaction.  Peanut allergens bind to IgE antibodies already attached to mast cells, causing aggregation and degranulation.
  C. Increased production of IgG antibodies: While IgG antibodies can play a role in other immune responses, they are not the primary mediators in the immediate, acute phase of a Type I hypersensitivity reaction.  IgG is more associated with secondary immune responses.
  D. Activation of the complement system:  The complement system can be activated via the classical pathway (involving antigen-antibody complexes) and contribute to inflammation.  In the context of a peanut allergy, IgE-mediated mast cell degranulation can trigger complement activation.
 3. Determine the least likely mechanism.
  Result: Increased production of IgG antibodies (option C) is the least likely primary mechanism contributing to the immediate, severe allergic symptoms.
  Verification: The other options are all key components of the immediate hypersensitivity response.  While IgG might be involved later in the immune response or in other aspects of the overall allergic reaction, it is not the primary driver of the immediate, severe symptoms.
## OPTION ANALYSIS
A ✓: Mast cell degranulation is crucial; histamine release causes the symptoms.
B :x: IgE cross-linking is the initiating event of the allergic reaction.
C :x: IgG is not a primary mediator in the immediate Type I hypersensitivity response.
D :x: Complement activation is a common secondary effect of mast cell degranulation and contributes to the inflammatory response.
## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing IgG and IgE roles in allergic reactions: Remember IgE is the primary antibody in Type I hypersensitivity, while IgG is involved in other immune responses.
  2.Overlooking the role of mast cells: Mast cells are central to the immediate phase of the allergic reaction.
 **Quick Tips**:
  1.Type I hypersensitivity = IgE, mast cells, histamine.
  2.IgG is associated with secondary immune responses, not the immediate allergic reaction.

A SUBRAMANYAM · Answer

Mast cell degranulation and release of histamine and other mediators.

A SUBRAMANYAM · Answer

Cross-linking of IgE antibodies bound to mast cells by peanut allergens.

A SUBRAMANYAM · Answer

The correct Option is "Increased production of IgG antibodies specific to peanut allergens."

A SUBRAMANYAM · Answer

Activation of the complement system via the classical pathway.

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