The major class of immunoglobulin present in human serum is?

Appeared in: AIIMS BBSR SNO - 2019

Explanation

IgG is the most abundant immunoglobulin in human serum, constituting about 75-80% of the total circulating antibodies.
It is the main antibody involved in the secondary (memory) immune response, providing long-lasting protection against pathogens.
IgG is unique in its ability to cross the placental barrier, conferring passive immunity from the mother to the fetus.

Option A: IgA is the second most abundant immunoglobulin in serum (10-15%), not the major one. Its primary role is in mucosal immunity.
Option B: IgM constitutes only about 5-10% of serum immunoglobulins. Although it is the first antibody to appear during an infection, its concentration is significantly lower than IgG.
Option C: IgE is present in the lowest concentration in serum (less than 0.01%). Its function is specialized for allergic reactions and defense against parasites.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classes and relative abundance of immunoglobulins in serum as background academic context rather than a clinical decision trigger.
Nurses should understand that measuring serum immunoglobulin levels is a key diagnostic tool for identifying immunodeficiency disorders (e.g., low IgG) or certain cancers like multiple myeloma (e.g., monoclonal spike of IgG).
Elevated levels of specific immunoglobulins can point to different clinical states: high IgM suggests a recent or current infection, while high IgE is a hallmark of allergic conditions or parasitic infestations.
The placental transfer of IgG is a vital concept in maternal and neonatal care, explaining how newborns are protected from infections in their first few months of life.

How to Approach the Question

First, identify the core of the question, which is asking for the 'major class' or most abundant type of 'immunoglobulin' specifically in 'human serum' (blood).
Recall the five main classes of immunoglobulins: IgG, IgA, IgM, IgD, and IgE.
Access your memory of the relative concentrations of these antibodies in the blood. A helpful mnemonic is 'GAMED', which lists them in order of decreasing abundance in serum (G > A > M > E > D).
Based on this order, IgG is the most prevalent immunoglobulin in the serum.
Compare this knowledge with the given options and select the one that matches IgG.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart A (pp 26-201 of 604) p. 101-103

E6 Harper's Illustrated Biochemistry2023 (pp 26-793 of 813) p. 630-632

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart B (pp 240-463 of 478) p. 92-94

Practise the full AIIMS BBSR SNO - 2019

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