Medical Forum

⚡ HYPERSENSITIVITY REACTIONS — GELL & COOMBS CLASSIFICATION
TYPE I — Immediate / Allergic
🧪 IgE mediated mast cell degranulation
⏰ Minutes to hours
💥 Histamine release
📌 Examples: ✅ Anaphylaxis
✅ Atopic asthma
✅ Urticaria
✅ Drug allergy
💡 “FAST & IgE”
TYPE II — Antibody Mediated Cytotoxic
🧪 IgG/IgM against cell surface antigens
⚙ Complement activation + opsonization
📌 Examples: ✅ Myasthenia gravis
✅ Graves disease
✅ Goodpasture syndrome
✅ Pemphigus vulgaris
✅ Rheumatic fever
💡 “Antibody attacks CELL”
TYPE III — Immune Complex Mediated
🧪 Ag-Ab complex deposition
⚙ Complement activation → neutrophil injury
📌 Examples: ✅ SLE
✅ PSGN
✅ Serum sickness
✅ HSP
✅ Arthus reaction
💡 “Complex gets deposited”
TYPE IV — Delayed / Cell Mediated
🧪 T-cell mediated (NO antibodies)
⏰ Delayed reaction
📌 Examples: ✅ Mantoux test
✅ Contact dermatitis
✅ Type 1 DM
✅ Multiple sclerosis
✅ GVHD
💡 “T-cells cause DAMAGE”
🔥 Transplant Rejection High Yield
🔴 Hyperacute
⏰ Minutes–hours
🧪 Type II hypersensitivity
💡 Due to preformed anti-HLA/ABO antibodies
🟠 Acute Cellular Rejection
🧪 T-cell mediated = Type IV
🟡 Acute Humoral Rejection
🧪 Antibody mediated
⭐ C4d deposition = IMPORTANT marker
⚫ Chronic Rejection
⏰ Months–years
💡 Irreversible fibrosis + arteriosclerosis