Which single feature best distinguishes the Arthus reaction from generalized serum sickness?
- A The Arthus reaction requires complement activation while serum sickness does not
- B The Arthus reaction is mediated by CD8 T cells rather than immune complexes
- C The Arthus reaction is a localized lesion produced by injection of antigen into a previously sensitized host with high circulating antibody ✓
- D The Arthus reaction appears 7 to 14 days after exposure whereas serum sickness appears within hours
Correct answer: C. The Arthus reaction is a localized lesion produced by injection of antigen into a previously sensitized host with high circulating antibody
Explanation
Both are type III immune complex reactions, but the Arthus reaction is a localized area of necrotizing vasculitis at the site of antigen injection in a sensitized individual with abundant preformed antibody, appearing within hours. Both depend on complement and neutrophils. The timing option reverses the two entities: serum sickness develops days to weeks after antigen exposure when antibody production begins, while the Arthus reaction appears within hours.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.