Immunotherapy

Basics of Immunotherapy - Immune Tune-Up

• Definition: Therapeutic administration of allergens to induce immune tolerance in allergic individuals, modifying the natural course of allergic disease.
• Goal: Achieve long-term symptom remission, prevent new sensitizations, and improve quality of life.
• Mechanism of Action:
  • Shifts immune response from Th2 (pro-allergic) to Th1 (protective).
  • Induces regulatory T cells (Tregs) & regulatory B cells (Bregs).
  • ↑ Production of blocking antibodies (IgG4).
  • ↓ Allergen-specific IgE levels over time.
  • ↓ Mast cell, basophil, and eosinophil reactivity.
• Core Principle: Gradual, controlled exposure to increasing doses of specific allergens.

⭐ Immunotherapy is the only disease-modifying treatment for allergic diseases.

Allergen Immunotherapy (AIT) - Allergy Avengers Assemble

• Goal: Induce allergen-specific tolerance, modify disease course.

• Mechanism: ↑Treg, IL-10, IgG4 (blocking Ab); ↓IgE, mast cell reactivity; Th2→Th1 shift.

• Indications:

  • Allergic rhinitis/conjunctivitis (mod-severe, persistent).
  • Allergic asthma (mild-mod, controlled, allergen confirmed).
  • Venom hypersensitivity (VIT highly effective).
  • Atopic dermatitis (select cases with aeroallergens).
  • Criteria: IgE-mediated allergy, allergen unavoidable, meds/avoidance insufficient.

• Contraindications:

  • Absolute: Uncontrolled asthma (FEV1 < 70%), active systemic autoimmune disease, malignancy.
  • Relative: Significant CVD, β-blockers/ACE-i (esp. SCIT), poor adherence, pregnancy (initiation).

• SCIT vs. SLIT:

⭐ Sublingual Immunotherapy (SLIT) generally has a better safety profile than Subcutaneous Immunotherapy (SCIT), especially regarding systemic reactions.

• Duration: Typically 3-5 years for sustained benefit post-discontinuation.
• 📌 AIT: Alleviates Immune Troubles!

AIT Practicalities - Dose, Duration, Dangers

• Dosing & Standardization:
  • Allergen extracts standardized: Bioequivalent Allergy Units (BAU), Allergy Units (AU).
  • Phases: Build-up (weekly/bi-weekly, gradually ↑dose) & Maintenance (monthly, constant highest tolerated dose).
  • Dose adjustments for missed doses, local/systemic reactions, or new allergen vials.
• Duration for Tolerance:

  ⭐ The standard duration for allergen immunotherapy (SCIT/SLIT) to achieve long-term tolerance is typically 3-5 years.

  • Decision to stop based on sustained clinical benefit and patient/physician assessment.
• Dangers & Management:
  • Local Reactions: Common (erythema, pruritus, swelling at injection site). Manage with cold compresses, topical corticosteroids, oral antihistamines.
  • Systemic Reactions (SRs): Range from mild (urticaria, rhinitis) to severe anaphylaxis.
    • Risk factors: Uncontrolled asthma, high allergen dose, dosing errors, concurrent illness.
    • 📌 Anaphylaxis: Epinephrine (0.01 mg/kg of 1:1000 solution IM, max 0.3-0.5 mg per dose), O2, IV fluids, antihistamines, corticosteroids. Observe for 4-6 hours.
  • Contraindications (Absolute): Severe uncontrolled asthma, active autoimmune disease. (Relative): Beta-blocker/ACE inhibitor use, significant cardiovascular disease.

Special ITx - Venom Victors & Food Frontiers

• Venom Immunotherapy (VIT):
  • Highly effective for Hymenoptera venom allergy (bees, wasps, ants).
  • Significantly ↓ anaphylaxis risk from future stings.
  • Protocol: Initial build-up, then maintenance every 4-8 weeks for 3-5 years.
  • Indications: Systemic reaction to sting + positive venom IgE or skin test.

  ⭐ Venom immunotherapy (VIT) is nearly 95-98% effective in preventing anaphylaxis from future stings in sensitized individuals.

• Food Immunotherapy (FIT):
  • Oral (OIT): Aims to desensitize to specific foods (e.g., peanut, milk, egg). Involves ingesting gradually increasing allergen doses. Requires strict medical supervision.
  • Sublingual (SLIT): Alternative to OIT for food allergy; potentially fewer systemic reactions but less established for food allergens compared to aeroallergens or VIT for venom.

High‑Yield Points - ⚡ Biggest Takeaways

• Allergen Immunotherapy (AIT) aims to induce allergen-specific immune tolerance.
• Key indications: severe allergic rhinitis, allergic asthma, and insect venom hypersensitivity.
• Mechanism: Shifts from Th2 to Th1 response, increases Treg cells and IgG4 blocking antibodies.
• Routes: Subcutaneous (SCIT) and Sublingual (SLIT) are primary methods.
• Duration: Typically 3-5 years for sustained, disease-modifying effects.
• SCIT carries a risk of anaphylaxis; requires post-injection observation.
• AIT can lead to long-term remission of allergic symptoms after completion of therapy.