Question

Identify the INCORRECT statement about the immunoglobulins (Ig)

• A. IgM forms pentamer
• B. IgA forms dimer
• C. IgD is the most abundant immunoglobulin
• D. IgE is associated with allergic reactions

Hint:

IgG is the most abundant immunoglobulin in serum, whereas IgM is pentameric and IgA commonly occurs as a dimer in secretions.

Answer 1

The Correct Option is C

Step 1: Understand immunoglobulins.
Immunoglobulins (antibodies) are glycoproteins produced by B-lymphocytes and plasma cells that help the immune system recognize and neutralize foreign antigens.

Step 2: Analyze IgM.
IgM is usually present as a pentamer in blood plasma. This pentameric structure makes it highly effective in agglutination and complement activation. Therefore, statement (A) is correct.

Step 3: Analyze IgA.
IgA commonly occurs as a dimer in secretions such as saliva, tears, and mucus. It plays a major role in mucosal immunity. Hence, statement (B) is correct.

Step 4: Analyze IgD.
IgD is present mainly on the surface of B cells and occurs in very low concentration in serum. It is not the most abundant immunoglobulin.

Step 5: Identify the most abundant immunoglobulin.
IgG is actually the most abundant immunoglobulin in human serum and is responsible for long-term immunity and secondary immune response.

Step 6: Analyze IgE.
IgE is associated with allergic reactions and defense against parasitic infections. Therefore, statement (D) is correct.

Step 7: Final conclusion.
Thus, the incorrect statement is
\[ \boxed{\text{IgD is the most abundant immunoglobulin}} \]
Hence, the correct answer is option (C).