Types Of Hypersensitivity: Pathology Hindi Lecture

𝐒𝐮𝐛𝐬𝐜𝐫𝐢𝐛𝐞 𝗙𝐨𝐫 𝗠𝐨𝐫𝐞 𝗜𝐧𝐟𝐨𝐫𝐦𝐚𝐭𝐢𝐨𝐧 𝐨𝐧 𝗛𝐞𝐚𝐥𝐭𝐡 👩‍⚕‍ 𝐚𝐧𝐝 𝗠𝐞𝐝𝐢𝐜𝐢𝐧𝐞💉🩺💊
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Types Of Hypersensitivity: Pathology Hindi Lecture -
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Introduction
Hypersensitivity reactions are exaggerated immune responses that cause tissue damage and various diseases. These reactions are classified into four types based on the underlying immune mechanisms. Each type of hypersensitivity has unique characteristics, mechanisms, and clinical manifestations.
Types of Hypersensitivity Reactions
Type I: Immediate Hypersensitivity (IgE-Mediated)
Mechanism: This type of hypersensitivity occurs when IgE antibodies bind to allergens (like pollen, dust mites, or food allergens). This triggers mast cells and basophils to release histamine and other inflammatory mediators.
Clinical Features:
Allergic Rhinitis 🤧 (Hay fever)
Asthma 😮‍💨 (Bronchial)
Anaphylaxis ⚠️ (Severe systemic reaction)
Urticaria (Hives)
💥 Pathology:
Upon initial exposure to an allergen, the immune system produces IgE antibodies.
On subsequent exposure, these IgE antibodies cause mast cells to release histamines and other chemicals, leading to symptoms like swelling, itching, and difficulty breathing.
Type II: Cytotoxic Hypersensitivity (Antibody-Mediated)
Mechanism: IgG or IgM antibodies bind to antigens on the surface of cells, marking them for destruction by the immune system. This leads to cell lysis or phagocytosis.
Clinical Features:
Hemolytic Anemia (Red blood cell destruction) 🩸
Blood Transfusion Reactions 💉
Rheumatic Fever 🔥
Graves' Disease
⚔️ Pathology:
Antibodies attach to the body's own cells, identifying them as foreign invaders.
This results in the destruction of these cells through mechanisms such as complement activation or phagocytosis.
Type III: Immune Complex Hypersensitivity
Mechanism: Immune complexes (antigen-antibody complexes) are formed and deposit in various tissues, leading to inflammation and tissue damage.
Clinical Features:
Systemic Lupus Erythematosus (SLE) 🦋
Post-Streptococcal Glomerulonephritis 💧
Rheumatoid Arthritis 🦴
Serum Sickness
🔬 Pathology:
Antigen-antibody complexes circulate in the bloodstream and deposit in tissues like the kidneys, joints, and blood vessels.
This deposition leads to complement activation and an inflammatory response, causing tissue injury.
Type IV: Delayed-Type Hypersensitivity (Cell-Mediated)
Mechanism: This hypersensitivity is mediated by T-cells, not antibodies. After exposure to the antigen, T-cells release cytokines, which activate macrophages and other immune cells.
Clinical Features:
Tuberculosis (TB) Skin Test 💉
Contact Dermatitis 🧴 (Poison Ivy)
Chronic Transplant Rejection 🏥
Multiple Sclerosis 🧠
⏳ Pathology:
Unlike other types, Type IV is delayed and can take 48-72 hours to manifest after antigen exposure.
T-cells activate and recruit other immune cells to the site of infection or inflammation, leading to local tissue damage.
Summary of Hypersensitivity Types:
Type I: IgE-mediated, immediate allergic reactions (e.g., asthma, anaphylaxis).
Type II: Antibody-mediated, cytotoxic (e.g., hemolytic anemia, blood transfusion reactions).
Type III: Immune complex-mediated, tissue deposition (e.g., lupus, rheumatoid arthritis).
Type IV: T-cell-mediated, delayed response (e.g., TB test, contact dermatitis).
Management & Treatment
Type I:
Antihistamines and Epinephrine (for anaphylaxis) to counteract histamine release.
Corticosteroids to reduce inflammation.
Type II:
Immunosuppressants to control the immune system.
Blood transfusions and plasma exchange in severe cases.
Type III:
Anti-inflammatory drugs (NSAIDs) to manage inflammation.
Immunosuppressive therapy in autoimmune diseases like lupus.
Type IV:
Topical steroids for dermatitis.
Immunomodulators for conditions like multiple sclerosis.
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[@amolkelkar7231]

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