In type III (immune complex) hypersensitivity, the Arthus reaction is a localized form. In the Arthus reaction, the antibody class that forms precipitating immune complexes leading to complement activation is:
- A IgE
- B IgA
- C IgG ✓
- D IgM alone
Correct answer: C. IgG
Explanation
The Arthus reaction is a type III hypersensitivity response mediated by locally precipitating antigen-IgG immune complexes that activate complement (classical pathway) and recruit neutrophils, causing localized vasculitis and necrosis at the injection site. IgE mediates type I (anaphylactic) hypersensitivity; IgA immune complexes can cause type III reactions in IgA nephropathy; IgM also activates complement but IgG is the classical mediator in Arthus.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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