autoimmune disease and hypersensitivity

Question 1

what is hypersensitivity?

Answer 1

a group of disorders in which the normally beneficial components of the immune response act in an exaggerated or innappropriate fashion to environmental antigens which do not normally cause tissue damage

Question 2

what is the difference between types I,II and III hypersensitivity and type IV sensitivity?

Answer 2

types I-III are mediated by antibodies, while type IV is caused by the innapropriate action of Th1 cells

Question 3

what is responsible for damage caused to tissues in cases of hypersensitivity?

Answer 3

the exaggerated immune response rather than the antigen itself

Question 4

how does type I hypersensitivity arise?

Answer 4

through inappropriate synthesis of IgE by the immune system.

Question 5

what is the difference between allergy and atopy?

Answer 5

atopy is the presence of innapropriate IgE with no clinical symptoms, in allergy the patient will display some form of clinical problem

Question 6

what is the IgE directed against in type I hypersensitivity?

Answer 6

environmental antigens(allergens)`

Question 7

how can environmental antigens be encountered?

Answer 7

airborne
ingested
injected
skin contact

Question 8

what happens in type I sensitivity after exposure to the environmental antigen?

Answer 8

mast cells and allergen specific IgE produced

release of inflammatory mediators

Question 9

what are some examples of inflammatory mediators ?

Answer 9

histamine (pre formed)

prostaglandins (newly synthesised)

Question 10

what are some of the effects of inflammatory mediators produced in type I hypersensitivity?

Answer 10

mucosal oedema
capillary leakage
secretions
smooth muscle contraction
vasodilatation

Question 11

what is type II hypersensitivity mediated by?

Answer 11

IgG or IgM antibodies

Question 12

what are the antibodies produced in type II hypersensitivity directed against?

Answer 12

antigens found on the surface of cells or fixed within certain tissues

Question 13

how are tissues damaged in type II hypersensitivity?

Answer 13

antibody binds to antigen
complement activation
fc binding of immunoglobulin and stimulation of phagocytes
antibody dependent cellular cytotoxicity (ADCC)

Question 14

what effects does type II hypersensitivity have on target cell function?

Answer 14

inhibition of function

stimulation

Question 15

where can the antigens come from in type II hypersensitivity?

Answer 15

external (exogenous) or self derived

Question 16

what do the clinical presentations of type III hypersensitivity arise from?

Answer 16

abnormal deposition of formed antigen (Ag) and antibody(Ab) complexes/immune complexes

Question 17

what happens in pathological immune complex formation?

Answer 17

abnormal immune complex formation causes the complexes to precipitate into tissues and cause inflammation

Question 18

what two forms of inflammation typically present in type III hypersensitivity?

Answer 18

serum sickness - systemic illness where immune complexes are deposited throughout many tissues
arthus reaction - localised disorder where complexes form locally in tissues

Question 19

what do the immune responses in type IV sensitivity occur as a result of?

Answer 19

contact with inert environmental substances or as a reaction to infection with certain micro-organisms

Question 20

what is the name for a low molecular weight environmental agent in a type IV hypersensitivity reaction?

Answer 20

HAPTEN

Question 21

what is the name for the host protein that the environmental agent binds to?

Answer 21

CARRIER

Question 22

why do environmental agents have to bind to host proteins in order to produce an immune response?

Answer 22

their molecular weight is too low individually to evoke an immune response

Question 23

how long does it take for clinical effects to present in type IV hypersensitivity?

Answer 23

typically 48-72 hours from antigen exposure

Question 24

what happens in type IV hypersensitivity reactions after the antigen has been presented?

Answer 24

cytokines are produced (overactivity/dysregulation), which leads to inflammation

Question 25

what is autoimmune disease?

Answer 25

group of clinical disorders characterised by tissue or organ damage mediated through aberrant cellular and/or humoral immunological mechanisms which are directed against autoantigens (self antigens)

Question 26

what is non-organ specific autoimmunity?

Answer 26

when specific autoantigens are present in a ubiquitous way throughout many tissues

Question 27

what is organ specific autoimmunity?

Answer 27

when the autoantigens causing the immune response are localised to specific tissues or organs

Question 28

what is tolerance with regard to autoimmune disease?

Answer 28

the process whereby the immune system avoids producing damaging reactions against self antigens

Question 29

what two types of tolerance are there?

Answer 29

central tolerance and peripheral tolerance

Question 30

what is central tolerance?

Answer 30

deletion of autoreactive T and B cells during cell maturation

Question 31

what is peripheral tolerance?

Answer 31

inhibiting the activity of autoreactive cells which escape the central tolerance process

Question 32

is immune recognition of self antigens always damaging?

Answer 32

no

Question 33

give an example of physiological (normal) immunity

Answer 33

when T cells recognise antigens which is complexed with self molecules
when antibodies recognise and bind portions of other antibodies, regulating their production and activity

Question 34

what is the aetiology of autoimmune disease?

Answer 34

interaction of:
genetic factors
immune regulatory factors
hormonal factors
environmental factors
"other" factors such as age, trauma and malignant disease

Question 35

what are the effector mechanisms involved in autoimmune disease?

Answer 35

identical to those in normal immune response:
cellular (T cell) or antibody (B cell) activity
antibody activation of complement mediated inflammation
immune complex formation
recruitment of innate immune components (phagocytes, cytokines)

Question 36

what is thought to be the cause of tolerance to an autoantigen being broken?

Answer 36

combination of one or more environmental factors combined with one or more genetic factors

Question 37

what are the consequences of tolerance to an autoantigen being broken?

Answer 37

allows for a potential or actual autoimmune response to occur against the autoantigen

Question 38

autoimmune disease encompasses a wide spectrum of disease that can be either organ-specific or non-organ specific, life-threatening or minor, true or false?

Answer 38

true