Serum sickness is due to which type of hypersensitivity?

Ans: C (Type III) Ref: Ananthnarayan R, Paniker CKJ. Textbook of Microbiology. 8th Edition. Hyderabad: Universities Press: 2009. Pg. 161-168Explanation:HYPERSENSITIVITYGell and Coomb classificationType I - IgE mediated- anaphylaxis and atopyType II- cytotoxic or cytolyticType III- immune complex mediatedType IV- T cell mediatedNote: Grave's disease is known as Type V hypersensitivityType I hypersensitivityAnaphylaxis-acute, systemic, potentially fatal formAtopy- chronic, localized, non fatal, familial form (Coca, 1923)Type I HS is mediated by IgE antibodiesEg of subatances associated with Type I HS:Proteins-foreign serum & vaccinesFood-nuts, eggs, milk,seafoodPlant pollenDrugs-penicillin, local anestheticsInsect products- venom (bees, wasps, ants dust mitesMold sporesAnimal hair and danderType II hypersensitivityReactions involve combination of IgG or IgM antibodies to cell fixed antigensExamples of type II reactionsCell surface antigensRBC- transfusion reactions, erythroblastosis fetalis, A.I.H.AWBC- neutropeniaPLATELETS-thrombocytopeniaTissue antigens Goodpasture's syndrome PemphigusType III hypersensitivityAntibodies (usually IgA ) directed against soluble antigensExamples of type III hypersensitivityArthus reaction- localized hemorrhagic necrosis following SC injection of antigen in sensitized rabbitsSerum sickness- systemic form appears 7-12 days after injection of foreign serumInfection (microbial antigen)-kidneys- leptospirosis, malaria. Post streptococcal glomerulonephritisAutoimmune diseases- (self antigen)- kidney, skin, jointsInhaled antigens (molds, plant pollen)-lung (Farmer's lung)Type IV hypersensitivityAlso called delayed hypersensitivity because it takes 48-72 hours to developInvolves TDTH cells (subset of TH cells)Cannot be passively transferred by serumExamples-contact dermatitis, tuberculin test (48- 72 hours) and granuloma (21-28 days)