Ans. B. Type 2 hypersensitivity reaction. {Ref, Robbins Basic Pathology 8th/ Table 5-1. ; 5-3.).Summary: Hypersensitivity reactionsTypeAntibodyComplementEffector cellsExamples1 (immediate)IgENoBasophil, mast cellHay fever, atopic dermatitis, insect venom sensitivity, anaphylaxis to drugs, some food allergies, allergy to animals and animal products, asthmaII (cytotoxic)IgG, IgMYesPMN, macrophages, NK cellsAutoimmune or drug-induced hemolytic anemia, transfusion reactions. HDNB, hyperacute graft rejection. Goodpasture disease, rheumatic feverII (noncytotoxic)IgGNoNoneMyasthenia gravis, Graves disease, type 2 diacetes mellitusIII (immune complex)IgG, IgMYesPMN, macrophagesSLE, RA, polyarteritis nodesa, poststreptococcal glomerulonephritis, Arthus reaction, serum sicknessIV (delayed DTH)NoneNoCTL, TH1, macrophagesTuberculin test, tuberculosis, leprosy, Hashimoto thyroiditis, poison ivy (contact dermatitis), acute graft rejection, GVHD, IDDM.Mechanisms of Immunologically Mediated DiseasesTypePrototype DisorderImmune MechanismsPathologic LesionsImmediate (type I) hypersensitivityAnaphylaxis, allergies, bronchial asthma (atopic forms)Production of IgE antibody ? immediate release of vasoactive amines and other mediators from mast cells; recruitment of inflammatory cells (late-phase reaction)Vascular dilation, edema, smooth muscle contraction, mucus production, inflammationAntibody-mediated (type II) hypersensitivityAutoimmune hemolytic anemia; Goodpasture syndrome, Rh incompatibilityProduction of IgG, IgM ?binds to antigen on target cell or tissue ?phagocytosis or lysis of target cell by activated complement or Fc receptors; recruitment of leukocytesPhagocytosis and lysis of cells; inflammation; in some diseases, functional derangements without cell or tissue injuryImmune complex- mediated (type III) hypersensitivitySystemic lupus erythematosus; some forms of glomerulonephritis; serum sickness; Arthus reactionDeposition of antigen-antibody complexes ?complement activation Precruitment of leukocytes by complement products and Fc receptors ?release of enzymes and other toxic moleculesInflammation, necrotizing vasculitis (fibrinoid necrosis)T-cell-mediated (type IV) hypersensitivityContact dermatitis; multiple sclerosis; type I diabetes; transplant rejection; tuberculosisActivated T lymphocytes ?(i) release of cytokines and macrophage activation; (ii) T-cell- mediated cytotoxicityPerivascular cellular infiltrates, edema, cell destruction, granuloma formationExamples of Antibody-Mediated Diseases (Type II Hypersensitivity)DiseaseTarget AntigenMechanisms of DiseaseClinicopathologic ManifestationsAutoimmune hemolytic anemiaAutoimmune thrombocytopenic purpuraErythrocyte membrane proteins (Rh blood group antigens, I antigen) Platelet membrane proteins (gp IIb: IIIa integrin)Opsonization and phagocytosis of erythrocytesOpsonization and phagocytosis of plateletsHemolysis, anemiaBleedingPemphigus vulgarisProteins in intercellular junctions of epidermal cells (epidermal cadherin)Antibody-mediated activation of proteases, disruption of intercellular adhesionsSkin vesicles (bullae)Vasculitis caused by ANCANeutrophil granule proteins, presumably released from activated neutrophilsNeutrophil degranulation and inflammationVasculitisGoodpasture syndromeNoncollagenous protein in basement membranes of kidney glomeruli and lung alveoliComplement- and Fc receptor- mediated inflammationNephritis, lung hemorrhageAcute rheumatic feverStreptococcal cell wall antigen; antibody cross- reacts with myocardial antigenInflammation, macrophage activationMyocarditis, arthritisMyasthenia gravisAcetylcholine receptorAntibody inhibits acetylcholine binding, down-modulates receptorsMuscle weakness, paralysisGraves disease (hyperthyroidism)TSH receptorAntibody-mediated stimulation of TSH receptorsHyperthyroidismInsulin-resistant diabetesInsulin receptorAntibody inhibits binding of insulinHyperglycemia, ketoacidosisPernicious anemiaIntrinsic factor of gastric parietal cellsNeutralization of intrinsic factor, decreased absorption of vitamin B12Abnormal erythropoiesis, anemiaExamples of Immune Complex-Mediated DiseasesDiseaseAntigen involvedClinicopathologic ManifestationsSystemic lupus erythematosusPoststreptococcal glomerulonephritisNuclear antigensStreptococcal cell wall antigen(s); may be "planted" in glomerular basement membraneNephritis, skin lesions, arthritis, othersNephritisPolyarteritis nodosaReactive arthritisSerum sicknessHepatitis B virus antigenBacterial antigens (Yersinia)Various proteins, such as foreign serum protein (horse anti-thymocyte globulin)Systemic vasculitisAcute arthritisArthritis, vasculitis, nephritisArthus reaction (experimental)Various foreign proteinsCutaneous vasculitisExamples of T-Cell-Mediated (Type IV) HypersensitivityDiseaseSpecificity of Pathogenic T cellsClinicopathologic ManifestationsType 1 diabetes mellitusAntigens of pancreatic islet ?cells (insulin, glutamic acid decarboxylase, others)Insulitis (chronic inflammation in islets), destruction of ?cells; diabetesMultiple sclerosisProtein antigens in CNS myelin (myelin basic protein, proteolipid protein)Demyelination in CNS with perivascular inflammation; paralysis, ocular lesionsRheumatoid arthritisUnknown antigen in joint synovium (type II collagen?); role of antibodies?Chronic arthritis with inflammation, destruction of articular cartilage and bone Peripheral neuropathy; Guiltain- Barre syndrome?Protein antigens of peripheral nerve myelinNeuritis, paralysisinflammatory bowel disease](Crohn's disease)Unknown antigen; may be derived from intestinal microbesChronic inflammation of ileum and colon, often with granulomas; fibrosis, strictureContact dermatitisEnvironmental chemicals, e.g., poisonivy (pentadecylcatechol)Dermatitis, with itching; usually short-lived, may be chronic with persistent exposure