Which of the following is the immunoglobulin, synthesized by plasma cells, that is responsible for allergic reactions?

Appeared in: JSSH Staff Nurse - 2019

Explanation

Immunoglobulin E (IgE) is the class of antibody primarily responsible for mediating Type I hypersensitivity, also known as allergic reactions.
IgE molecules are synthesized by plasma cells and bind to high-affinity receptors on the surface of mast cells and basophils.
When an allergen binds to these IgE antibodies, it triggers the degranulation of mast cells and basophils.
This degranulation releases inflammatory mediators like histamine, which cause the characteristic symptoms of allergy, such as itching, swelling, and difficulty breathing.

Option A: IgM is the first antibody produced in response to an initial infection (primary immune response). It is a large pentameric molecule primarily involved in activating the complement system and agglutinating pathogens.
Option B: IgA is the main antibody found in mucosal secretions like saliva, tears, and breast milk. Its primary role is to provide localized protection on mucosal surfaces against pathogens.
Option C: IgD is found in very small amounts in the blood and is primarily located on the surface of B lymphocytes, where it functions as a B-cell antigen receptor, helping to initiate the immune response.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Functions of Immunoglobulins and Allergic Reactions as background academic context rather than a clinical decision trigger.
Understanding the role of IgE is fundamental for nurses in managing patients with allergic conditions like asthma, allergic rhinitis, and atopic dermatitis.
Nurses educate patients on allergen avoidance and administer medications like antihistamines (which block histamine receptors) or mast cell stabilizers.
A severe, life-threatening allergic reaction mediated by IgE is anaphylaxis, which requires immediate nursing intervention, including the administration of epinephrine.

How to Approach the Question

First, identify the key concepts in the question: 'immunoglobulin' and 'allergic reactions'.
Recall the five major classes of immunoglobulins: IgG, IgA, IgM, IgD, and IgE. A useful mnemonic is 'GAMED'.
Systematically review the primary function of each immunoglobulin class.
Associate 'allergic reactions' or 'Type I hypersensitivity' specifically with the function of IgE.
Eliminate the other options (IgM, IgA, IgD) based on their distinct primary roles (primary response, mucosal immunity, B-cell receptor, respectively).
Select IgE as the correct answer because its defining role is to mediate allergic responses by triggering mast cell degranulation.

Concept Tested & Keywords

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E6 Microbiology Essentials Sastry 4e Part 1 p. 150-152

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 1382-1384

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Attempt every question from this paper in a timed mock, then review the full solution for each one.