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Flashcards in HYPERSENSITIVITY Deck (66):
1

what is hypersensitivity?

extreme physical sensitivity to particular substances or conditions

2

how is hypersensitivity classified?

type 1
type 2
type 3
type 4

3

what is type 1 hypersensitivity?

IgE-mediated, immediate type hypersensitivity
(IgE-mediated degranulation of mast cells)

4

what is type 2 hypersensitivity?

Cytotoxic reaction (complement lysis/ADCC)

5

what is type 3 hypersensitivity?

Immune complex reaction- (complement activation)

6

what is type 4 hypersensitivity?

T-cell mediated, delayed type hypersensitivity

7

give an example of type 1 hypersensitivity

allergic rhinitis, allergic asthma, urticaria

8

give an example of type 2 hypersensitivity

drug allergy

9

give an example of type 3 hypersensitivity

allergic vasculitis

10

give an example of type 4 hypersensitivity

allergic contact eczema

11

how long does type 1 hypersensitivity occur?

30 minutes

12

how long does type 2 hypersensitivity occur?

days

13

how long does type 3 hypersensitivity occur?

6 - 8 hours

14

how long does type 4 hypersensitivity occur?

48 - 72 hours

15

what is the organ manifestation of type 1 hypersensitivity?

skin/mucosa 45%
resp tract 25%
GI tract 20%
Cardiovascular system 10%

16

Why is allergy on the increase?

Hygiene hypothesis
Change to a clean environment in developed countries skews the immune response to a Th2 response
Th1/inflammatory immune defects are also on the rise (MS, IBD)

17

what are the causes of type 1 hypersensitivity?

genetics
environment

18

what causes Allergic rhinitis / asthma?

IgE mediated reaction to inhaled allergens

19

what does rhinitis affect?

upper airways

20

what are symptoms of rhinitis?

nasal itch
Sneeze
Rhinorhoea
nasal obstruction

21

what does asthma affect?

lower airways

22

what are symptoms of asthma?

bronchoconstriction, mucus hypersecretion
Wheeze
Breathlessness
Cough

23

what is a direct/rapid route in to blood stream?

sting
ingestion

24

what affects the outcome of a reaction?

route
dose

25

what is anaphylaxis?

Catastrophic lowering of blood pressure, airway constriction, swelling of epiglottis

26

how is anaphylaxis treated?

Epinephrine relaxes bronchiole smooth muscle

27

what do eosinophils do?

mainly kill parasites via reacting towards opsonised parasites

28

what causes degranulation?

large amounts of IL5 / IL3 in allergy cause

29

what causes atopic dermatitis?

Chronic inflammation (initiated via IgE), apopotosis of keratinocytes
Leaky skin (filaggrin defect) binds keratin fibres together (leaky skin-allergens)

30

what is allergic contact dermatitis?

Important cause of occupational disease
Hapten

31

what type are Non IgE allergic diseases?

type 2
type 3

32

what are type 2 Non IgE allergic diseases?

IgG mediated destruction of blood cells/platelets-autoimmune hemolytic anemia.
Hemolytic disease of the newborn Thrombocytopenia. Change in signalling

33

what are type 3 Non IgE allergic diseases?

IgG immune complex deposition on vessel walls-
Arthus reaction
Serum Sickness, arthritis, vasculitis, nephritis, farmers’ lung

34

what are type 4 hypersensitivity reactions mediated by?

by antigen-specific effector T cells

35

what is Allergic contact dermatitis mediated by?

via lipid soluble urushiol oil haptens binding MHCI

36

what is coeliac disease?

small intestine is hypersensitive

37

what is tolerance?

describes immune cell non-reactivity to antigens

38

what are the different types of tolerance?

self
neonatal
acquired

39

what is self tolerance?

Tolerance to innate antigens

40

what is neonatal tolerance?

Antigens encountered within hours after birth are tolerated

41

what is acquired tolerance?

a

42

what does self tolerance and self recognition allow?

the maturation f both T and B cells

43

what does the breakdown of immunological tolerance lead to?

to autoimmune disease

44

what do T cells need to have to function correctly?

recognise self MHCs (self recognition)
they must display self tolerance

45

can B cells show self tolerance?

yes

46

what leads to autoimmune disease?

the loss of self tolerance

47

how do normally pre T cells in the thymus develop self recognition?

via positive selection

48

how is self tolerance acquired?

by negative selection

49

what do some of the T cells produced become?

fully mature immunocompetent cells

50

what can happen to self reactive T cells after they leave the thymus?

can be deleted if they contact an unrecognised self protein.

51

what is acquired tolerance?

describes a non reactivity to an antigen that should cause an immune response

52

what are the properties of allergens?

small proteins, soluble, long lasting in environment, mucosal exposure, often proteases

53

what can protease allergens activate?

PAR receptors

54

what do antibodies attach to in type 2?

to epitopes on self cells

55

what do antibodies in type 2 induce?

activation of compliment

56

what does activation of compliment in type 2 result in?

in vasodilatation and migration of phagocytic cells to the effected tissue

57

what does activation of compliment in type 2 promote?

activation of membrane attack complex

58

what do type 2 antibodies refer to?

antibodies that attacked self blood cells, used to describe antibodies that target other tissues

59

what is type 3 caused by?

by antigen antibody complexes

60

what are the antigens in type 3?

can be self antigens or non-self antigens such as bacteria

61

what do antigens in type 3 promote?

inflammatory response

62

what are the 2 types of type 3 hypersensitivity?

local
systemic

63

what is Local form Type 3 Hypersensitivity?

If an individual is immunised against an antigen, subcutaneous injection of a high conc of that antigen induces an inflammatory response peaking within 7 hours at that site

64

what is systemic form Type 3 Hypersensitivity?

Antigen complexes may form systemically - promoting system wide inflammatory responses

65

what is type 4 related to?

to Helper T cells interacting with activated cytotoxic T cells, NK cells or macrophages

66

what happens with type 4?

Response is delayed and cannot be transferred in the serum