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Hypersensitivity reactions

Hypersensitivity reactions. http://xenia.sote.hu/depts/pathophysiology. L ászló L. Tornóci Semmelweis University Institute of Pathophysiology. Classification. Type 1 hypersensitivity reaction. Hypersensitivity of immediate type. T erminol o g y. Hypersensitivity of immediate type

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Hypersensitivity reactions

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  1. Hypersensitivity reactions http://xenia.sote.hu/depts/pathophysiology László L. Tornóci Semmelweis University Institute of Pathophysiology

  2. Classification

  3. Type 1 hypersensitivity reaction Hypersensitivity of immediate type

  4. Terminology • Hypersensitivity of immediate type fastest reaction of all four • Allergy rare, tissue damage • Anaphylaxy generalized, severe reaction • Atopy an umbrella term for genetic susceptibility

  5. Clinicalsignificance • Very common, increasing trend • 30-40% of the population in developed countries • gets more and more common since1800 • very great (10-15-times) geographical difference • The anaphylactic reactionis rare, butsever (may cause death)

  6. Diseases • urticaria • allergic rhinitis • atopic eczema • asthma • food allergy • anaphylaxy

  7. Bee sting

  8. Food allergy

  9. Common allergens Airways: • pollen (grass, tree, flower) • household dust(mite: Dermatophagoides pteronyssinus) • animal hair(cat, dog) Enteral/parenteral (anaphylactic reaction): • drug(e.g. penicillin) • food(milk, fish, shellfish, peanut) • sting(bee, wasp)

  10. Dermatophagoides mite

  11. Type 1: pathomechanism

  12. Activation of mast cells

  13. Activation of Th1 and Th2 cells

  14. Factors involved in Th1/Th2 activation

  15. Heredity A few genes causing atopy • MHC class II • FcRI ( subunit) • IL-4 cytokine cluster • IL-4 receptor ( subunit)

  16. Diagnostics, total IgE

  17. Diagnostics, skin prick test

  18. The advantage of type 1 reaction

  19. Type 2 hypersensitivity reaction Antibody-mediated cytotoxicity

  20. Diseases • Incompatibleblood transfusion • Autoimmune hemolytic anamia (AIHA) • Goodpasture syndrome • Pemphigus vulgaris (Ag: desmoglein)

  21. Mechanisms • complement activation  MAC  cytolysis • complement activation, chemotaxis • ADCC reaction • „frustrated phagocytosis”

  22. “Frustrated phagocytosis”

  23. Symptoms of the transfusion reaction • fever • BP drop • lumbar pain • chest pain • nausea, vomiting

  24. Maternal-fetal Rh incompatibility

  25. Erythroblastosis fetalis

  26. Autoimmune hemolysisThe “innocent bystander” mechanism

  27. Diagnostics: indirect Coombs’ test

  28. Type 2 reaction without tissue damage Blocking antibodies

  29. Type 3 hypersensitivity reaction Immune complex reaction

  30. Circulating immune complexes

  31. Diseases • classic serum sickness • serum sickness-like reaction caused by drugs • immune complex reaction caused by infections • systemic autoimmune diseases

  32. The time course of serum sickness

  33. Occurrance of immune complexes

  34. Pathomechanism

  35. Type 4 hypersensitivity reaction Delayed type hypersensitivity reaction

  36. Types of delayed hypersensitivity reaction

  37. Contact allergy

  38. Contact eczema

  39. Tuberculin test

  40. Leprosy

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