1. Hypersensitivity reactions
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. Clinical significance
Very common, increasing trend
30-40% of the population in developed countries
gets more and more common since 1800
very great (10-15-times) geographical difference
The anaphylactic reaction is rare, but sever (may cause death)

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

7. Bee sting

8. Food allergy

9. Common allergens Airways: Enteral/parenteral (anaphylactic reaction):
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 Incompatible blood 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 hemolysis The “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
Cause
Antigen
Place of deposition
chronic infection
microbial Ag
site of infection, kidneys
autoimmunity
autoantigen
kidneys, joints, vessels, skin
external
environmental Ag
lungs

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
Type of reaction
Time of maximal reaction
Jones-Mote
1 day
contact
2-3 days
tuberculin
granulomatous
at least 2 weeks

37. Contact allergy

38. Contact eczema

39. Tuberculin test

40. Leprosy