Question:hard
A child suffering from recurrent chronic infections with encapsulated bacteria has a deficiency of which IgG subclass?
A child suffering from recurrent chronic infections with encapsulated bacteria has a deficiency of which IgG subclass?
Show Hint
Which IgG subclass answers polysaccharide capsule antigens?
Updated On: Jun 23, 2026
- IgG1
- IgG2
- IgG3
- IgG4
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: The clinical signature is repeated infection by capsule-bearing bacteria, so ask which antibody handles polysaccharide capsules.
Step 2: Among the four IgG subclasses, IgG2 is the specialist for polysaccharide antigens, providing the main protection against encapsulated organisms.
Step 3: In young children this IgG2 anti-polysaccharide response matures slowly, so an IgG2 defect leaves them vulnerable to pneumococcus and H. influenzae.
Step 4: IgG1 and IgG3 respond to proteins and IgG4 to chronic/allergic stimuli, so none of them fits, leaving IgG2 as the deficient subclass.
\[\boxed{\text{IgG2}}\]
Step 2: Among the four IgG subclasses, IgG2 is the specialist for polysaccharide antigens, providing the main protection against encapsulated organisms.
Step 3: In young children this IgG2 anti-polysaccharide response matures slowly, so an IgG2 defect leaves them vulnerable to pneumococcus and H. influenzae.
Step 4: IgG1 and IgG3 respond to proteins and IgG4 to chronic/allergic stimuli, so none of them fits, leaving IgG2 as the deficient subclass.
\[\boxed{\text{IgG2}}\]
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