HYPERSENSITIVITY

Question 1

what is hypersensitivity?

Answer 1

extreme physical sensitivity to particular substances or conditions

Question 2

how is hypersensitivity classified?

Answer 2

type 1
type 2
type 3
type 4

Question 3

what is type 1 hypersensitivity?

Answer 3

IgE-mediated, immediate type hypersensitivity

IgE-mediated degranulation of mast cells

Question 4

what is type 2 hypersensitivity?

Answer 4

Cytotoxic reaction (complement lysis/ADCC)

Question 5

what is type 3 hypersensitivity?

Answer 5

Immune complex reaction- (complement activation)

Question 6

what is type 4 hypersensitivity?

Answer 6

T-cell mediated, delayed type hypersensitivity

Question 7

give an example of type 1 hypersensitivity

Answer 7

allergic rhinitis, allergic asthma, urticaria

Question 8

give an example of type 2 hypersensitivity

Answer 8

drug allergy

Question 9

give an example of type 3 hypersensitivity

Answer 9

allergic vasculitis

Question 10

give an example of type 4 hypersensitivity

Answer 10

allergic contact eczema

Question 11

how long does type 1 hypersensitivity occur?

Answer 11

30 minutes

Question 12

how long does type 2 hypersensitivity occur?

Answer 12

days

Question 13

how long does type 3 hypersensitivity occur?

Answer 13

6 - 8 hours

Question 14

how long does type 4 hypersensitivity occur?

Answer 14

48 - 72 hours

Question 15

what is the organ manifestation of type 1 hypersensitivity?

Answer 15

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

Question 16

Why is allergy on the increase?

Answer 16

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)

Question 17

what are the causes of type 1 hypersensitivity?

Answer 17

genetics

environment

Question 18

what causes Allergic rhinitis / asthma?

Answer 18

IgE mediated reaction to inhaled allergens

Question 19

what does rhinitis affect?

Answer 19

upper airways

Question 20

what are symptoms of rhinitis?

Answer 20

nasal itch
Sneeze
Rhinorhoea
nasal obstruction

Question 21

what does asthma affect?

Answer 21

lower airways

Question 22

what are symptoms of asthma?

Answer 22

bronchoconstriction, mucus hypersecretion
Wheeze
Breathlessness
Cough

Question 23

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

Answer 23

sting

ingestion

Question 24

what affects the outcome of a reaction?

Answer 24

route

dose

Question 25

what is anaphylaxis?

Answer 25

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

Question 26

how is anaphylaxis treated?

Answer 26

Epinephrine relaxes bronchiole smooth muscle

Question 27

what do eosinophils do?

Answer 27

mainly kill parasites via reacting towards opsonised parasites

Question 28

what causes degranulation?

Answer 28

large amounts of IL5 / IL3 in allergy cause

Question 29

what causes atopic dermatitis?

Answer 29

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

Question 30

what is allergic contact dermatitis?

Answer 30

Important cause of occupational disease | Hapten

Question 31

what type are Non IgE allergic diseases?

Answer 31

type 2 | type 3

Question 32

what are type 2 Non IgE allergic diseases?

Answer 32

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

Question 33

what are type 3 Non IgE allergic diseases?

Answer 33

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

Question 34

what are type 4 hypersensitivity reactions mediated by?

Answer 34

by antigen-specific effector T cells

Question 35

what is Allergic contact dermatitis mediated by?

Answer 35

via lipid soluble urushiol oil haptens binding MHCI

Question 36

what is coeliac disease?

Answer 36

small intestine is hypersensitive

Question 37

what is tolerance?

Answer 37

describes immune cell non-reactivity to antigens

Question 38

what are the different types of tolerance?

Answer 38

self neonatal acquired

Question 39

what is self tolerance?

Answer 39

Tolerance to innate antigens

Question 40

what is neonatal tolerance?

Answer 40

Antigens encountered within hours after birth are tolerated

Question 41

what is acquired tolerance?

Answer 41

a

Question 42

what does self tolerance and self recognition allow?

Answer 42

the maturation f both T and B cells

Question 43

what does the breakdown of immunological tolerance lead to?

Answer 43

to autoimmune disease

Question 44

what do T cells need to have to function correctly?

Answer 44

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

Question 45

can B cells show self tolerance?

Answer 45

yes

Question 46

what leads to autoimmune disease?

Answer 46

the loss of self tolerance

Question 47

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

Answer 47

via positive selection

Question 48

how is self tolerance acquired?

Answer 48

by negative selection

Question 49

what do some of the T cells produced become?

Answer 49

fully mature immunocompetent cells

Question 50

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

Answer 50

can be deleted if they contact an unrecognised self protein.

Question 51

what is acquired tolerance?

Answer 51

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

Question 52

what are the properties of allergens?

Answer 52

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

Question 53

what can protease allergens activate?

Answer 53

PAR receptors

Question 54

what do antibodies attach to in type 2?

Answer 54

to epitopes on self cells

Question 55

what do antibodies in type 2 induce?

Answer 55

activation of compliment

Question 56

what does activation of compliment in type 2 result in?

Answer 56

in vasodilatation and migration of phagocytic cells to the effected tissue

Question 57

what does activation of compliment in type 2 promote?

Answer 57

activation of membrane attack complex

Question 58

what do type 2 antibodies refer to?

Answer 58

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

Question 59

what is type 3 caused by?

Answer 59

by antigen antibody complexes

Question 60

what are the antigens in type 3?

Answer 60

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

Question 61

what do antigens in type 3 promote?

Answer 61

inflammatory response

Question 62

what are the 2 types of type 3 hypersensitivity?

Answer 62

local | systemic

Question 63

what is Local form Type 3 Hypersensitivity?

Answer 63

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

Question 64

what is systemic form Type 3 Hypersensitivity?

Answer 64

Antigen complexes may form systemically - promoting system wide inflammatory responses

Question 65

what is type 4 related to?

Answer 65

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

Question 66

what happens with type 4?

Answer 66

Response is delayed and cannot be transferred in the serum