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Questions and Answers
What type of hypersensitivity reaction primarily involves IgE antibodies?
What type of hypersensitivity reaction primarily involves IgE antibodies?
- Type IV hypersensitivity
- Type I hypersensitivity (correct)
- Type III hypersensitivity
- Type II hypersensitivity
What is a common symptom associated with localized Type III hypersensitivity reactions?
What is a common symptom associated with localized Type III hypersensitivity reactions?
- Nasal congestion
- Localized swelling and bleeding (correct)
- Itchy rash all over the body
- Severe migraines
Which of the following is a diagnostic test commonly used for detecting allergic reactions?
Which of the following is a diagnostic test commonly used for detecting allergic reactions?
- Skin prick test (correct)
- Complete blood count
- Urinalysis
- Magnetic resonance imaging
What is a typical treatment option for managing allergic reactions?
What is a typical treatment option for managing allergic reactions?
Mast cell activation is primarily associated with which type of immune response?
Mast cell activation is primarily associated with which type of immune response?
What is the main mechanism involved in delayed-type hypersensitivity (DTH)?
What is the main mechanism involved in delayed-type hypersensitivity (DTH)?
How is a positive delayed-type hypersensitivity reaction typically identified?
How is a positive delayed-type hypersensitivity reaction typically identified?
What role do macrophages play in delayed-type hypersensitivity responses?
What role do macrophages play in delayed-type hypersensitivity responses?
Which of the following is NOT a typical sensitizing agent that can cause contact dermatitis?
Which of the following is NOT a typical sensitizing agent that can cause contact dermatitis?
What occurs during the initial exposure in a delayed-type hypersensitivity reaction?
What occurs during the initial exposure in a delayed-type hypersensitivity reaction?
What does a tuberculin skin test primarily indicate?
What does a tuberculin skin test primarily indicate?
Which cytokines are primarily involved in the effector phase of a delayed-type hypersensitivity reaction?
Which cytokines are primarily involved in the effector phase of a delayed-type hypersensitivity reaction?
What symptom typically results from the T-cell mediated response in contact dermatitis?
What symptom typically results from the T-cell mediated response in contact dermatitis?
What role do IgE antibodies play in type I hypersensitivity reactions?
What role do IgE antibodies play in type I hypersensitivity reactions?
Which of the following symptoms is NOT typically associated with type I hypersensitivity reactions?
Which of the following symptoms is NOT typically associated with type I hypersensitivity reactions?
Which diagnostic test is commonly used for identifying type I hypersensitivity reactions?
Which diagnostic test is commonly used for identifying type I hypersensitivity reactions?
Which treatment option is effective for managing acute allergic symptoms?
Which treatment option is effective for managing acute allergic symptoms?
What triggers mast cell activation in an allergic reaction?
What triggers mast cell activation in an allergic reaction?
What type of mediators are released from mast cells upon activation?
What type of mediators are released from mast cells upon activation?
Which of the following allergens is most likely to elicit a type I hypersensitivity response?
Which of the following allergens is most likely to elicit a type I hypersensitivity response?
Which statement regarding IgE levels in allergic individuals is accurate?
Which statement regarding IgE levels in allergic individuals is accurate?
Which mechanism is primarily induced by the FcεRI receptor in allergic reactions?
Which mechanism is primarily induced by the FcεRI receptor in allergic reactions?
What component is NOT a known allergen associated with type I hypersensitivity?
What component is NOT a known allergen associated with type I hypersensitivity?
What is the primary purpose of using ELISA in allergy diagnostics?
What is the primary purpose of using ELISA in allergy diagnostics?
Which of the following describes the interaction between IgE antibodies and multivalent antigens in allergic individuals?
Which of the following describes the interaction between IgE antibodies and multivalent antigens in allergic individuals?
What is a significant risk associated with type I hypersensitivity reactions, particularly in severe cases?
What is a significant risk associated with type I hypersensitivity reactions, particularly in severe cases?
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Study Notes
Hypersensitivity Overview
- Hypersensitivity is an undesirable reaction produced by the normal immune system, leading to allergies and autoimmune responses.
- Reactions can be damaging, uncomfortable, or occasionally fatal.
- Excessive immune response in sensitized individuals can result in tissue damage.
Types of Hypersensitivity
- Four main types:
- Type I: Immediate (allergic reactions)
- Type II: Cytotoxic hypersensitivity
- Type III: Immune complex-mediated hypersensitivity
- Type IV: Delayed-type hypersensitivity (cell-mediated)
Type I Hypersensitivity
- Involves IgE antibodies and is characterized as immediate and anaphylactic.
- Allergies are initiated by interaction between IgE and a multivalent antigen.
- Free circulating IgE is usually at low concentrations in healthy individuals.
Common Allergens
- Plant pollens: Rye grass, ragweed, Timothy grass, Birch tree
- Drugs: Penicillin, sulfonamides, local anesthetics, salicylates
- Foods: Nuts, seafood, eggs, milk, peas, beans
- Other allergens include insect products and dust mites.
Mechanism of Allergic Reactions
- IgE antibodies cross-link Fcε receptors on innate immune cells (mast cells and basophils).
- High-affinity IgE receptor (FcεRI) triggers allergic symptoms through signaling pathways.
- Resulting mediators include histamine, leukotrienes, prostaglandins, and chemokines, causing various symptoms.
Symptoms and Diagnosis
- Symptoms may include eczema, asthma, and anaphylaxis.
- Skin testing is a common diagnostic method; it involves injecting small quantities of known allergens to observe swelling and redness.
Type II Hypersensitivity
- Cytotoxic hypersensitivity involves complement activation and phagocyte involvement.
Type III Hypersensitivity
- Characterized by immune complexes that are not cleared leading to inflammation and tissue damage.
- Involves antigens from persistent infections, inhaled antigens, injected materials, and autoimmune reactions.
- Examples: Serum sickness, systemic lupus erythematosus.
Immunocomplex Diseases
- Immune complex injuries are dependent on the cause, antigen, and deposition sites (e.g., local inflammation in kidneys, lungs, or joints).
Type IV Hypersensitivity (DTH)
- Purely cell-mediated and requires previous sensitization; T cells are the primary actors.
- Characterized by macrophage recruitment, often demonstrated in conditions like contact dermatitis (e.g., poison ivy).
- Detection involves skin tests, with positive responses indicating sensitized T cells.
Contact Dermatitis
- Can be triggered by reactive chemicals binding to skin proteins, initiating a strong cell-mediated response.
Summary of Effects
- Delayed-type hypersensitivity can result in granulomas and severe tissue damage if the antigen persists, as seen in conditions such as leprosy and tuberculosis.
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