NIMHANS Nursing Officer - 2019
Applied Microbiology & Infection control
Easy
Which immunoglobulin is mediated by type 1 hypersensitivity reaction?
Appeared in: NIMHANS Nursing Officer - 2019
Explanation
- Type I hypersensitivity reactions are also known as immediate or allergic reactions.
- This type of reaction is mediated by Immunoglobulin E (IgE).
- On initial exposure to an allergen, the body produces IgE antibodies that bind to the surface of mast cells and basophils.
- Upon re-exposure, the allergen cross-links the IgE on these cells, triggering rapid degranulation and the release of inflammatory mediators like histamine.
- This process leads to the classic symptoms of allergy, such as vasodilation, increased vascular permeability, and smooth muscle contraction, which can manifest as conditions like anaphylaxis, asthma, or urticaria (hives).
Why Other Options Were Wrong
- Option A: IgD's primary role is to act as an antigen receptor on the surface of B-lymphocytes, helping to initiate the immune response. It does not mediate the effector phase of hypersensitivity.
- Option B: IgG is the key mediator for Type II (cytotoxic) and Type III (immune complex) hypersensitivity reactions, not Type I.
- Option C: IgA is the main antibody found in mucosal secretions (e.g., saliva, tears, gut lining) and provides localized immunity. It is not the primary mediator of systemic allergic reactions like Type I hypersensitivity.
Related Visual
Clinical Relevance
- Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Gell & Coombs classification of hypersensitivity reactions, specifically Type I as background academic context rather than a clinical decision trigger.
- Recognizing the signs of a Type I hypersensitivity reaction, especially anaphylaxis, is a critical nursing skill. Early signs include urticaria, angioedema, wheezing, and hypotension.
- The nurse's immediate priorities in managing anaphylaxis are to maintain the airway, support breathing, and restore circulation (ABCs). This includes administering high-flow oxygen and preparing for potential intubation.
- Administering intramuscular epinephrine is the first-line treatment for anaphylaxis. Nurses must be prepared to administer it quickly and monitor the patient's response.
How to Approach the Question
- First, identify the key terms in the question: 'Type 1 hypersensitivity' and 'immunoglobulin'.
- This is a factual recall question that requires knowledge of the different types of hypersensitivity reactions and the specific antibodies involved in each.
- Recall the Gell & Coombs classification system for hypersensitivity.
- Mentally review the four types: Type I (IgE), Type II (IgG/IgM), Type III (IgG/IgM), and Type IV (T-cells).
- Match 'Type 1' with its corresponding mediator, which is IgE.
- Select the option 'IgE' as the correct answer.
Concept Tested & Keywords
- Concept Tested: Gell & Coombs classification of hypersensitivity reactions, specifically Type I.
- Stem keywords: immunoglobulin, type 1 hypersensitivity reaction
- Lead-in keywords: Which
Question ID
Q8awwxxaxOFh41_slCFfA6
Reference Book
E6 Microbiology Essentials Sastry 4e Part 1 p. 150-152
E6 Pharmacology Katzung 16e p. 1522-1524
E6 Biochemistry U Satyanarayana— Part 2 (pp 421-820 of 840) p. 358-360
Practise the full NIMHANS Nursing Officer - 2019
Attempt every question from this paper in a timed mock, then review the full solution for each one.
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