<prompt> A patient was on treatment with penicillin. He developed pallor but there was no shortness of breath, urticaria or wheezing. On investigation, antibodies against penicillin were found in his blood. What is the type of hypersensitivity reaction that most likely occurred in this patient?Type I hypersensitivityType II hypersensitivityType III hypersensitivityType IV hypersensitivity  <response>: Ans. b. Type II hypersensitivity Ref: Robbins 9 c p205.8e p653, 202Penicillin hypersensitivity reaction is an example of type II, antibody mediated hypersensitivity reaction.Examples of type II hypersensitivity Auto immune hemolytic anemia Autoimmune thrombocytopenic purpura Pemphigus vulgaris ANCA mediated vasculitis Goodpasture syndrome Myasthenia gravis Acute rheumatic fever Graves disease Insulin resistant diabetes Pernicious anemia Mechanisms of drug-induced immunohemolytic anemiaAntigenic drugsHapten ModelTolerance-breaking drugsAuto antibody Model Hemolysis usually follows large, intravenous doses of the offending drugQ Occurs 1 to 2 weeks after therapy is initiatedExamples: Penicillin and cephalosporins, bind to the red cell membrane and are recognized by anti-drug, as in penicillin-induced hemolysisQ Quinidine-induced hemolysisQ, the antibodies recognize a complex of the drug and a membrane protein. These drugs, of which the antihypertensive agent alpha- methyldopa is the prototype, induce the production of antibodies against red cell antigens, particularly the Rh blood group antigensQ. Types of HypersensitivityType 1 lgEQType IIIgG and lgMQ Cytotoxic, complement mediated lysisQType IIImmune complex IgM and IgGType IVDelayed hypersensitivity Cellular immunityIncludes: Local: Eczema, Hay fever. Asthma AtopyQ Systemic: AnaphylaxisExamples: Theoblad Smith phenomenon:Q This is anaphylaxis in guinea pigs. PK reaction Prusnitz Kunster:Q Demonstrate that IgE is homocytotropic i.e. species specific. Casonis test: Immediate type IgE HypersensitivityIncludes: Complement mediated lysis Antibody dependent cell mediated toxicity formerly classified as type lQ Changes in cellular function former type VQ Increased function: Graves diseaseQ Decreased function: M. GravisQ PhagocytosisExamples:- Those with Ag on RBC:- Blood transfusion reactionQ- Hemolytic anemia e.g. with I.M. and mycoplasmaQ Those with Ag on Neutrophils: AgranulocytosisQ Those with Ag on platelets: ITPdeg Those with Ag on basement membrane: GoodpasturesQ syndrome Pemphigus vulgaris ANCA mediated vasculitis Acute rheumatic fever Insulin resistant diabetes Pernicious anemiaIncludes: Local: Arthus reactionQ Systemic: Serum sicknessQExamples: Shicks testQ Post streptococcal G.N.Q Detected by RAJI AssayQIncludes: Tuberculin testQ Lepromin textQ Contact dermatitis Jones-mote reaction cutaneous basophilic hypersensitivityQ Graft rejection chronicQ 