Type I Hypersensitivity: Pathogenesis and clinical findings Definition: Production of lgE Antibodies that bind to harmless allergens and induce mast cell degranulation, leading to an allergic reaction. "Sensitization" to Allergen: Initial exposure to allergen (ex. dust, pollen, foods, drugs) -> Patient's immune system mistakenly recognizes allergen as potentially harmful -> Formation of allergen-specific plasma cells that secrete lgE-antibodies -> Allergen-specific lgE Abs persist in body after clearance of allergen Second Exposure to Allergen: Pre-formed lgE binds allergen, creating an allergen-antibody complex -> Allergen-antibody complexes bind to mast cells, causing them to "degranulate": release the pro-inflammatory molecules within them (i.e. histamine) into the blood => • Increased Vascular permeability • Smooth muscle contraction in airways • Mucus secretion • Inflammatory cells recruited Complications: • Acute Asthma • Antibiotic Allergies (ex. penicillin & cephalosporin) • Food Allergies (ex. peanuts) • Hay fever (allergic rhinitis to airborne particles like pollen & dust) • Urticaria (hives) • Allergic conjunctivitis • Anaphylaxis #TypeI #Type1 #HypersensitivityReaction #Allergy #Immunology #pathophysiology
