TABLE 1

Types and classifications of HSRsb

HSR classificationReaction typeImmunologic mechanismHSR name/symptom
IIgE-mediated, immediate-type hypersensitivityAntigen exposure causes IgE-mediated activation of mast cells and basophils with release of allergic mediators (histamine, prostaglandins, and leukotrienes).Anaphylaxis, angioedema, bronchospasm, urticaria (hives)
IIAntibody dependentAn antigen or hapten on the cell binds to antibody (IgG), leading to cell or tissue injury.Hemolytic anemia, thrombocytopenia, neutropenia
IIIImmune complex diseaseAntigen-antibody (IgG) complexes cause damage by complement activation and/or recruitment of neutrophils.Serum sickness
IVCell-mediated, delayed-type hypersensitivityAntigen exposure activates T cells, which then mediates tissue injury.Maculopapular rash, organ-specific reactions,a SJS/TEN, DRESS syndrome
  • a Organ-specific reactions include acute interstitial nephritis, an immune-mediated nephritis, and immune-mediated hepatitis.

  • b Data are from references 2 to 4. Abbreviations: HSR, hypersensitivity reaction; SJS/TEN, Stevens-Johnson syndrome/toxic epidermal necrolysis; DRESS, drug rash eosinophilia and systemic symptoms.