Question

Which of the following statements is INCORRECT about immunoglobulin E (IgE)?

• A. IgE molecule have an array of physiological functions, such as Type I hypersensitivity reactions as well as parasitic infections.
• B. The heavy chain of IgE contains an extra domain.
• C. High IgE levels are found in anaphylactic shock.
• D. IgE is a pentamer and like IgM it have 10 F(ab) regions

Hint:

Remember the structural states of immunoglobulins:
- IgG, IgD, IgE \(\rightarrow\) Always Monomers.
- IgA \(\rightarrow\) Monomer or Dimer.
- IgM \(\rightarrow\) Pentamer.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
This question tests our understanding of the structural characteristics, classes, and physiological roles of immunoglobulins (antibodies), with a focus on Immunoglobulin E (IgE).

Step 2: Detailed Explanation:
Let us systematically evaluate each of the statements to identify the incorrect one:
- Option (A): "IgE molecule have an array of physiological functions, such as Type I hypersensitivity reactions as well as parasitic infections."
This statement is correct. IgE is the primary mediator of Type I (immediate) hypersensitivity reactions (like allergies and asthma).
Additionally, IgE plays a vital protective role against extracellular helminthic (parasitic worm) infections by coating the parasites and facilitating eosinophil activation.
- Option (B): "The heavy chain of IgE contains an extra domain."
This statement is correct. The heavy chain of IgE (epsilon, \(\epsilon\)) and IgM (mu, \(\mu\)) contains four constant domains (\(C_H1\), \(C_H2\), \(C_H3\), and \(C_H4\)), whereas IgG, IgA, and IgD have only three constant domains.
This extra domain (\(C_H4\)) replaces the flexible hinge region found in other immunoglobulins.
- Option (C): "High IgE levels are found in anaphylactic shock."
This statement is correct. Anaphylactic shock is a severe, systemic Type I hypersensitivity reaction.
It is triggered by the systemic degranulation of mast cells and basophils, which is initiated by the cross-linking of antigen to IgE molecules bound to high-affinity \(Fc\epsilon RI\) receptors on these cells.
- Option (D): "IgE is a pentamer and like IgM it have 10 F(ab) regions"
This statement is incorrect. IgE exists physiologically as a monomer (consisting of two heavy chains and two light chains), not a pentamer.
Consequently, a single IgE molecule has only two antigen-binding \(F(ab)\) sites.
IgM is the only immunoglobulin class that typically forms a pentameric structure (containing 10 \(F(ab)\) regions).

Step 3: Final Answer:
The incorrect statement regarding IgE is Option (D).
Therefore, the correct choice is Option (D).