Hypersensitivity reactions

Type 1 Hypersensitivity reaction - 

Immediate reactions / Ig E antibody mediated / Anaphylactic reactions / Atopic reactions 

Examples -

• Anaphylaxis (Antisera [Ex-anti-tetanus serum] , Drugs , Beesting , Wasp , Food) (Pruritus , rash , Pulmonary edema , Bronchospasm)

• Angioedema (Subcutaneous tissues +/- Submucosal tissues circumscribed non-pitting edema of face , neck , eyelids , lips , extremities , larynx , oral cavity , gut)

• Bronchial asthma

• Cutaneous anaphylaxis (Urticaria/Hives , Wheel , Flare)

• Hay fever / Seasonal allergic rhinitis due to Pollen

Type 2 Hypersensitivity reaction - 

Antibody Mediated / Cytotoxic

Ig G (or) Ig M antibody mediated

Examples -

• Autoimmune hemolytic anemia (autoantibodies against RBC antigens)

• Erythroblastosis fetalis (maternal isoantibodies against fetal RBC)

• Idiopathic thrombocytopenic purpura (autoantibodies against surface components of normal platelets)

• Acute hemolytic transfusion reactions (Preformed recipient antibody binds to transfused RBC antigens)

• Good pasture syndrome (autoantibodies against Glomerular basement membrane of kidney)

• Grave's disease (autoantibodies against TSH receptor)

• Myasthenia gravis (autoantibodies against acetylcholine receptors)

• Pemphigus Vulgaris (autoantibodies against Desmoglein 3- Epidermal desmosomal adhesion protein of Cadherin family)

• Pernicious anemia (autoantibodies against Intrinsic factor)

• Leucopenia with agranulocytosis (autoantibodies against leucocytes)

• Type 1 diabetes mellitus (autoantibodies against Insulin receptor)

• Immune infertility/Male sterility (Antisperm antibody)

• Rheumatic fever (Cross reactivity , Molecular mimicry [Streptococcal cell wall M protein and Human cardiac valves)] , autoantibodies against heart)

Type 3 Hypersensitivity reaction -

 Immune complex mediated / Arthus reaction

Ig G (or) Ig M antibody mediated

Examples -

• SLE 

• Serum sickness

• Rheumatoid arthritis

• Post streptococcal glomerulonephritis

• Farmer's lung (Hypersensitivity Pneumonitis)

• Type 2 lepra reaction

• Henoch-schonlein purpura

• Polyarteritis nodosa

• Drug induced hypersensitivity vasculitis

Type 4 Hypersensitivity reaction - 

Delayed hypersensitivity / T-cell mediated

Examples -

• Tuberculin reaction

• Lepromin test

• Type 1 lepra reaction

• DRESS (Drug Reactions with eosinophilia and systemic symptoms)

• SJS (Steven Johnson Syndrome)

• TEN (Toxic Epidermal Necrolysis)

• Acute generalized exanthematous pustulosis

• Contact dermatitis

• Guttate Psoriasis

• Crohn's disease

• chronic graft rejection

• Graft vs Host reaction

• Sarcoidosis

• Multiple sclerosis

• Primary biliary cholangitis

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