Medicine & USMLE

Immunoglobulin E (IgE)

  1. Immunoglobulin A (IgA)
  2. Immunoglobulin G (IgG)
  3. Immunoglobulin M (IgM)
  4. Immunoglobulin E (IgE)
  5. Immunoglobulin D (IgD)


Immunoglobulin E (IgE) is a type of antibody responsible for mediating immunity against parasites and allergic reactions. IgE can directly bind parasites (esp. helminths) and activate other immune cells to produce an immune response. Importantly, cross-linking of IgE happens when multiple molecules of IgE bind nearby antigens, and this clumping of IgE causes activation of basophils and mast cells, which bind to IgE using Fc-epsilon receptors. This eventually results in histamine release, generating a local inflammatory response. While IgE normally targets parasitic antigens, it may incorrectly target harmless allergens, which explains its key role in allergic reactions.

Key Points

  • Immunoglobulin E (IgE)
    • Binds to antigens on parasites and allergens
      • Mediates defense against parasites (esp. worms / helminths)
      • Mediates allergic reactions / anaphylaxis
        • Also called Type I Hypersensitivity Reactions
    • Fc region of bounds IgE recognized by Mast Cells and Basophils
      • Fc-epsilon receptor binds to IgE in close proximity (IgE crosslinking)
      • Activation releases histamine
        • immunoprotective vs parasites
        • pathogenic in allergy, atopy, and anaphylaxis
    • Fc region of bound IgE by Eosinophils
      • Activation releases major basic protein (toxic to parasites)
    • Found in the lowest concentration in serum