Types of Hypersensitivity Reactions
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Questions and Answers

Which immune globulin is primarily involved in Type I hypersensitivity reactions?

  • IgM
  • IgE (correct)
  • IgG
  • IgA

    • What is a common example of a Type II hypersensitivity reaction?

  • Latex allergy
  • Systemic lupus erythematosus
  • Hemolytic reactions (correct)
  • Bee stings

    • What time frame can Type III hypersensitivity reactions typically occur after exposure to an antigen?

  • Immediately
  • 3 - 10 hours (correct)
  • 24 - 48 hours
  • 15 - 30 minutes

    • Which cells are primarily involved in the mechanism of Type IV hypersensitivity?

    <p>T lymphocytes</p> Signup and view all the answers

    What is a hallmark symptom of acute allergic conjunctivitis?

    <p>Itching</p> Signup and view all the answers

    Which condition is specifically associated with Type I hypersensitivity?

    <p>Food allergies</p> Signup and view all the answers

    Which mediator is released from mast cells during a Type I hypersensitivity reaction?

    <p>Histamine</p> Signup and view all the answers

    What type of hypersensitivity would most likely involve an immune complex deposition?

    <p>Type III</p> Signup and view all the answers

    Which condition is associated with delayed hypersensitivity reactions?

    <p>Contact dermatitis</p> Signup and view all the answers

    Which symptom is most commonly associated with chronic allergic conjunctivitis?

    <p>Pinkish hyperemia</p> Signup and view all the answers

    What is the first-line approach for treating mild allergic conjunctivitis?

    <p>Cold compresses and OTC vasoconstrictors</p> Signup and view all the answers

    Which of the following treatments is NOT advised for patients under 3 years old?

    <p>Naphcon-A (Naphazoline 0.025%/Pheniramine maleate 0.3%)</p> Signup and view all the answers

    What is the primary function of mast cell stabilizers in the treatment of allergic conjunctivitis?

    <p>To prevent the release of histamine and other inflammatory mediators</p> Signup and view all the answers

    Which of the following medications is considered a dual-action agent for acute allergic conjunctivitis?

    <p>Ketotifen 0.025% solution</p> Signup and view all the answers

    For moderate to severe allergic conjunctivitis, which treatment addition is appropriate?

    <p>Mild steroids or NSAIDs</p> Signup and view all the answers

    During which season should maintenance therapy for allergic conjunctivitis be pre-treated?

    <p>Allergy season</p> Signup and view all the answers

    What common side effect could occur from using antihistamines for ocular allergic reactions?

    <p>Rhinitis and headaches</p> Signup and view all the answers

    What is a recommended treatment option for chronic allergic conjunctivitis during episodes of exacerbation?

    <p>Cold compresses and artificial tears</p> Signup and view all the answers

    What is primarily indicated for the maintenance of chronic allergic conjunctivitis?

    <p>Mast cell stabilizers and oral antihistamines</p> Signup and view all the answers

    What is the common action of the following ocular medications: Olopatadine and Azelastine?

    <p>Dual action - H1 blocker and mast cell stabilizer</p> Signup and view all the answers

    Study Notes

    Types of Hypersensitivity Reactions

    • Type I Hypersensitivity (IgE-mediated): A rapid, allergic reaction triggered by IgE antibodies. It involves mast cell degranulation and release of inflammatory mediators (histamine, prostaglandins, leukotrienes). Symptoms manifest within 15-30 minutes after exposure. Examples include bee stings, latex, and penicillin. Involves skin, eyes, nasopharynx, bronchopulmonary, and gastrointestinal tract.
    • Type II Hypersensitivity (Cytotoxic): Mediated by IgG and IgM antibodies, leading to cell destruction. Antigens are often endogenous. Examples include hemolytic reactions, myasthenia gravis (MG) and certain graft rejections.
    • Type III Hypersensitivity (Immune Complex): Caused by immune complex deposition, which activates complement proteins and leads to inflammatory reactions. Symptoms may take 3-10 hours to appear. Examples include serum sickness, hypersensitivity pneumonitis, lupus, and some types of vasculitis (e.g., Polyarteritis nodosa).
    • Type IV Hypersensitivity (Delayed/Cell-mediated): Involves T lymphocytes, monocytes/macrophages, not antibodies. Examples include contact dermatitis, tuberculin skin testing (PPD), graft rejection, and some autoimmune diseases

    Acute Allergic Conjunctivitis

    • Causes: Most often Type I hypersensitivity, including seasonal allergies ("hay fever"), food allergies, and atopic conditions.
    • Signs: Pinkish conjunctiva (hyperemia), chemosis (swelling), small papillae, potential lid swelling (chronic cases may show dark pigmentation), and a Dennie-Morgan fold (suggestive of atopic dermatitis).
    • Symptoms: Severe itching, watery discharge, stringy mucus, possible associated rhinitis, sinusitis, and postnasal drip.
    • Treatment: Varies by severity. Mild cases can be managed with cold compresses and over-the-counter (OTC) vasoconstrictors. Moderate to severe cases may require antihistamines, mast cell stabilizers, topical steroids/NSAIDs, and artificial tears/lubricants. Maintenance therapy (1-3 months) involving pre-season treatments may also be beneficial.

    Chronic Allergic Conjunctivitis

    • Characteristics: Long-standing, recurrent with exacerbations.
    • Treatment: Similar to acute treatment but with a focus on maintenance therapy, including artificial tears, cold compresses, mast cell stabilizers, and/or oral antihistamines as needed.

    Ocular Anti-allergic Medications

    • Antihistamines: H1 blockers (e.g., Naphcon-A, Emadine, etc.). Differences include strength, and a need to be cautious in pre-school children, due to side effects which could appear, if used excessively.
    • Mast Cell Stabilizers: Reduce mast cell activity reducing allergic reaction. More effective than antihistamines in this respect. (Cromolyn sodium, Lodoxamide, Nedocromil, Pemirolast). Usually for mild or seasonal acute allergic conjunctivitis and some forms of VKC/GPC.
    • Corticosteroids: Example is Loteprednol (Alrex). Used sparingly due to possible side effects including IOP changes. Lower concentrations have anti-inflammatory actions in allergic conditions
    • Other combination agents: Many medications available; dual or triple action, which combines antihistamines , mast cell stabilizers and reduce eosinophil chemotaxis (bepotastine, olopatadine, azelastine, epinastine, Alcaftadine)

    Adjunctive Systemic Therapy

    • Oral Anti-histamines: Benadryl, Chlor-Trimeton (older generation), Allegra, Claritin, Zyrtec are examples. Use caution with angle-closure glaucoma prone patients.
    • Steroidal Nasal Sprays: Fluticasone, Budesonide are used for nasal allergy support.

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    Description

    Explore the various types of hypersensitivity reactions in the immune system, including Type I, II, and III reactions. This quiz covers the mechanisms, symptoms, and examples of each type, helping you understand their distinct characteristics and implications in allergy and autoimmune disorders.

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