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Allergy is a range of symptoms due to inappropriat ...
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Flashcards in this deck (28)

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  • What is an allergy?

    A range of symptoms due to inappropriate activation of the immune system to benign substances.

    allergy immune_system

  • What are the ways the immune system can kill pathogens?

    • Phagocytosis
    • Disrupt cell membrane
    • Release chemicals
    • Kill infected cells
    immune_system pathogens

  • Where are mast cells located?

    Beneath the epithelial surface.

    mast_cells anatomy

  • What can mast cells do?

    • Release inflammatory mediators
    • Recruit effector cells
    • Increase vascular permeability
    • Cause smooth muscle contraction
    mast_cells functions

  • What triggers granule release in mast cells?

    Secondary exposure to antigen causing crosslinking between IgE/ receptor on mast cell surface

    mast_cells granules

  • What are the components of mast cell granules?

    • Histamine (vasodilatation, increased capillary permeability, chemokinesis, bronchoconstriction)
    • Heparin
    • Tryptase (activates C3)
    • Eosinophilic chemotactic factor (eosinophil chemotaxis)
    • Platelet activating factor
    mast_cells granules

  • What does histamine do?

    • Vasodilatation
    • Increased capillary permeability
    • Chemokinesis
    • Bronchoconstriction
    histamine functions

  • What are the types of hypersensitivity reactions?

    • Type I: Immediate (IgE)
    • Type II: Cytotoxic (IgM, IgG)
    • Type III: Immune complex
    • Type IV: Cellular immune mechanisms
    hypersensitivity immune_response

  • How is IgE produced?

    When Th2 cells instruct B cells to class switch into IgE plasma cells.

    ige immune_system

  • What signals are needed for CD4⁺ T cell activation?

    1. Specificity: TCR + CD4 binds to antigen–MHC II.
    2. Costimulation or survival: CD28 binds B7-1/B7-2.
    3. Cytokines: Dendritic cell secretes cytokines to drive differentiation.
    t_cells activation

  • What cytokines drive T cell differentiation?

    • IL-12, IFN-γ → Th1
    • IL-4 → Th2
    • IL-6 + TGF-β → Th17
    • IL-21, IL-6 → Tfh
    • TGF-β, IL-2 → Treg
    cytokines t_cell_differentiation

  • What is sensitization in allergy?

    The presence of IgE antibodies to a particular substance.

    sensitization allergy

  • What does allergy testing detect?

    Sensitization but does not prove the presence of allergy.

    allergy_testing diagnosis

  • What is skin prick testing used for?

    To detect localized mast cell degranulation in the skin.

    skin_prick_testing allergy

  • What are reasons for positive SPT without clinical allergy?

    • Patient reacts on skin but does not react in other pathway GI respiratory.
    • Low IgE levels may not cause symptoms.
    • Skin mast cells may be more reactive.
    spt allergy

  • What is atopy?

    An inherited predisposition to develop IgE-mediated hypersensitivity to common environmental antigens.

    Can be modified by environmental factor

    atopy genetics

  • What components lead to IgE sensitization?

    1. Allergen entry.
    2. APC processes allergen and presents peptide with 3 signals
    3. Naïve CD4⁺ T cell differentiates into Th2 cell under IL4.
    4. IgE binds FcεRI receptors on mast cells and basophils → mast cells are now “sensitised”.
    ige_sensitization immune_response

  • What are the cytokines produced by Th2 cells?

      • IL-4 & IL-13 → class switching in B cells → IgE production.
      • IL-5 → activates eosinophils.
    immunology cytokines

  • What occurs during the effector phase of Type I hypersensitivity?

    Re-exposure to allergen causes IgE cross-linking on mast cells, leading to degranulation and mediator synthesis.

    immunology hypersensitivity

  • Define Type I hypersensitivity reactions.

    Immediate hypersensitivity due to mast cell/basophil activation via IgE cross-linking.

    immunology hypersensitivity

  • What are the phases of Type I hypersensitivity?

    • Immediate reaction (minutes)
    • Late-phase reaction (hours)
    immunology hypersensitivity

  • What occurs during the immediate reaction of Type I hypersensitivity?

    Mast cell granule release: histamine, tryptase, proteases, heparin.

    immunology hypersensitivity

  • What are the effects of histamine release during an immediate reaction?

    • Vasodilation
    • Increased vascular permeability
    • Bronchoconstriction
    • Itching
    immunology histamine

  • What is involved in the late-phase reaction of Type I hypersensitivity?

    Mast cells and Th2 cells release cytokines & chemokines, recruiting eosinophils and leukocytes.

    Causing chronic inflammation and tissue damage

    immunology hypersensitivity

  • What are some examples of Type I hypersensitivity?

    • Allergic rhinitis
    • Asthma
    • Urticaria
    • Anaphylaxis
    immunology hypersensitivity

  • What are localized reactions in IgE-mediated allergic reactions?

    • Respiratory tract: allergic rhinitis, asthma
    • Skin: urticaria, eczema
    • GI tract: food allergies
    • Eyes: conjunctivitis
    immunology allergies

  • What is a systemic reaction in IgE-mediated allergic reactions?

    Anaphylaxis: widespread degranulation causing hypotension, airway obstruction, angioedema, urticaria.

    immunology anaphylaxis

  • What are the clinical signs of anaphylaxis?

    • Hypotension/shock
    • Airway obstruction
    • Angioedema
    • Urticaria
    • Wheeze
    immunology anaphylaxis