The immunoglobulin present in most abundant quantity?

NVS- 2025

Applied Microbiology & Infection control

Easy

Appeared in: NVS- 2025

Explanation

Immunoglobulin G (IgG) is the most abundant antibody isotype in the blood and extracellular fluid, constituting about 75-85% of the total immunoglobulins in serum.
Its primary roles include neutralizing toxins, opsonizing pathogens for phagocytosis, and activating the complement system.
IgG is the only immunoglobulin that can cross the placenta, providing crucial passive immunity to the fetus and newborn.
It is the predominant antibody produced during a secondary (memory) immune response, providing long-term immunity.

Option A: IgM is the third most abundant immunoglobulin in the serum, making up only 5-10% of the total. Although it is the largest antibody and the first to be produced in a primary immune response, its concentration is significantly lower than IgG.
Option B: IgE is the least abundant immunoglobulin in the serum, accounting for less than 0.01%. Its primary function is related to allergic reactions and defense against parasites, not general circulation in high quantities.
Option C: IgA is the second most abundant immunoglobulin in the serum, comprising 10-15% of the total. While it is the most abundant antibody in mucosal secretions (like saliva, tears, and breast milk), its serum concentration is lower than that of IgG.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Relative abundance of immunoglobulin isotypes in serum as background academic context rather than a clinical decision trigger.
Measuring IgG levels is crucial in diagnosing immunodeficiencies, autoimmune diseases, and chronic infections. Low levels may indicate a compromised immune system, while high levels can suggest chronic inflammation or infection.
The transfer of maternal IgG across the placenta is a fundamental concept in neonatal immunity, protecting the newborn for the first few months of life until their own immune system matures.
What if the question asked for the most abundant immunoglobulin in breast milk? The answer would change to IgA, which provides critical mucosal immunity to the infant's gastrointestinal tract.

How to Approach the Question

First, identify the core of the question, which is asking to identify the 'most abundant' immunoglobulin.
Recognize that unless specified otherwise (e.g., 'in secretions'), this question refers to the concentration in the blood serum.
Recall the relative percentages of the different immunoglobulin classes in the serum.
Compare the options: IgG (75-85%), IgA (10-15%), IgM (5-10%), and IgE (<0.01%).
Conclude that IgG has the highest concentration, making it the correct answer.

Concept Tested & Keywords

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