Hypersensitivity Reactions · Pathology

What is the role of the 'early phase' in Type I hypersensitivity?

  1. Infiltration of eosinophils and neutrophils causing tissue damage
  2. Mast cell degranulation releasing histamine and heparin
  3. Production of IgG to neutralize the allergen
  4. Activation of the MAC complex on the cell surface
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Correct answer: Mast cell degranulation releasing histamine and heparin

The early phase occurs within minutes of allergen exposure and is dominated by the release of pre-formed mediators from mast cells. This causes the classic wheal-and-flare reaction, bronchospasm, and increased mucus secretion.

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