Hypersensitivity Flashcards
(88 cards)
1
Q
what is a hypersensitivity reaction
A
this is a state of altered reactivity in which the body reacts with an immune response to a foreign agent
2
Q
what is an allergen
A
a foreign antigen that causes an allergic reaction
3
Q
how can allergens be
A
airbone
food
medication
4
Q
what are some airborne allergens
A
pollen or dust
5
Q
how are intolerances and allergies different
A
allergies involve the immune system but intolerances involve the digestive system
6
Q
what are the four types of hypersensitivity
A
I
II
III
IV
7
Q
describe type I hypersensitivty
A
this is IgE mediated and involves mast cells and basophils
8
Q
what are examples of type 1 hypersensitive reactions
A
cutaneous atopy and anaphylaxis
9
Q
describe type II hypersensitive reactions
A
cytotoxic responses involving NK cells, complement and T cells
10
Q
what is an example of type II hypersensitivity
A
haemolytic anaemia
11
Q
what is an example of type III hypersensitive reactions
A
arthus reaction
serum sickness
oral erythema multiforme
12
Q
describe type III hypersensitive reactions
A
these are immune complex responses involving complement and neutrophils
13
Q
what is an example of a type IV hypersensitive reactions
A
tuburculosis and crohns
14
Q
describe type IV hypersensitivity
A
cell mediated response reaction involving t cells and macrophages
15
Q
explain the form of allergens
A
allergens tend to be proteins and have the ability to elicit an immune response but some can be haptens ie non proteins
16
Q
describe hapten allergens
A
these are small molecules that can be recognised by a specific antibody but they cannot elicit an immune response
17
Q
how do haptens elicity antibody or t cell responses
A
they are small and first must be chemically linked to a protein molecule called a carrier
18
Q
what is it called when haptens bind to carrier proteins
A
conjugation
19
Q
which is the most common type of hypersensitivity
A
type I
20
Q
what produces IgE
A
b cells
21
Q
what do mast cells and basophils release in type I reactions
A
histamines
22
Q
describe how type I IgE mediated hypersensitivity works
A
as allergens binds to IgE antibodies, IgE cross linking induces degranulation
23
Q
what can cause type I hypersensitive reactions
A
anaphylaxis
hay fever
hives
exzema
allergies to certain foods
24
Q
where do antigens bind on antibodies
A
the FC receptor region
25
what is an important thing to note about eosinophils and basophils in the context of the exam
they are parasite eaters involved in allergic reactions
basophils are involved in allergic reactions alongside mast cells
26
what do b cells produce in response to microbial antigens
IgM
27
when do b cells carry out a class switch and what do they switch to
when responding to specific antigens
usually IgG but in allergic reactions it is IgE in order to drive the allergic response
28
how does IgE work
it binds to specific receptors on mast cells and basophils to stimulate and result in degranulation of histamine and other chemical mediators into the surrounding tissue
29
where does IgE bind to on mast cells
Fc receptor
30
where does IgE bind on basophils
CD63
31
what is elicitation
this is when IgE recognises an allergen and next exposure it will bind rapidly and cause immediate degranulation of immune cells
32
list the stages to type I hypersenstivity reactions
- upon first exposure to the allergen, APC prcesses the antigen and presents it to a TH2 cell
- TH2 cells release Il4 and Il12 to activate the b cells
- b cells will proliferate and differentiate into plasma cells to synthesise and secrete IgE antibody
- IgE binds to mast cells by Fc region and sensitises the mast cells
- upon subsequent exposure to the allergen, mast cells with IgE bind to antigen and release inflammatory molecules, resulting in allergy symptoms
33
what are the main roles of histamine
vasodilation
increased vascular permeability of blood vessels
smooth muscle contraction
bronchoconstriction
neurotransmission (sensation of itching in allergies)
34
what is anaphylaxis
widespread allergic reaction to a particular allergen found throughout the body through histamine and anaphylatoxins
35
what is atopy
general predisposition
36
what is a cutaneous reaction
one that is localised to a particular tissue
37
examples of cutaneous hypersensitivity reactions
- allergic rhinitis
- atopic dermatitis
- asthma
- allergic reaction to chlorhexidine
38
what does systemic anaphylaxis lead to
anaphylactic shock
39
describe what the body undergoes during systemic anaphylaxis
mast cell degranulation releases histamine
complement system produces anaphylatoxins through the classical pathway
the two molecules have widespread impacts on respiration and cardiovascular health
40
what are the two key symptoms of anaphylactic shock
- narrowing of the larynx where there is laryngeal oedema
- tightening of the bronchioles to narrow the airways and reduce breathing
41
what type of hypersensitivity is associated with skin patch tests
type I
42
describe the tests that can be taken to determine type I hypersensitivity
skin patch
blood test
oral challenge
43
how does a skin patch test work
wheal and flare reaction
to help identify the allergen
44
how does a blood test work to determine type I hypersensitivity
measures IgE levels in the blood
45
how does oral challenge hypersensitivity
diagnoses food allergies
46
what are antihistamines
histamine receptor agonist
47
what is hydrocortisone
this blocks histamine synthesis
48
what does epinephrine do
this reverses the effects of granules through vasodilation
49
describe the possible immunological treatments for type I hypersensitivity
hyposensitivity through injecting allergens
IgE to IgG production
50
what is the main treatment for type I hypersensitivity
just avoiding the allergy
51
what is the classification system that defines the four types of hypersensitivity
gell and coombs
52
what mediates type I allergies
IgE
53
how can type I hypersensitivity be defined
either localised or systemic
localised is cutaneous atopy
systemic is anaphylaxis
54
which molecules drive type I hypersensitive reactions
histamine and anaphylatoxins
55
describe type II hypersensitivity
this involves activation of complement by antibody binding to an antigen
56
which antibody is involved in type II hypersensitivity
not IgE
57
what are the antigens involved in type II hypersensitivity
cell surface auto antigens or allergens
58
how are infected cells lysed during type II hypersensitivity
cell is lysed by membrane attack complex formation from the complement system and antibody dependent cellular cytotoxicity
59
what produces autoantigens
the host
60
what are the type II hypersensitivity reactions driven against
host tissues or components of the human body. cells are lysed by membrane attack complex which is formed from the complement cascade or through antibody dependent cellular cytotoxicity
61
which cells are involved in antibody dependent cytotoxicity
natural killer cells or CD8+ t cells
62
what is the ultimate response of type II hypersensitivity
lysis of the cell
63
describe the type II hypersensitive response when there is transfusion of mis matched blood type
- donated type A blood with type A antigens enters the bloodstream of type B recipient
- anti-A antibodies in plasma of type B recipient binds to donated type A red blood cells
- bound anti-A antibodies activate complement cascade, causing hemolysis and release of haemoglobin
64
what happens to erythrocytes when they bind antierythrocyte autoantibodies
- autoantibodies activate complement; antibody and complement coated erythrocytes are targeted for destruction by macrophages in the spleen
- complement activation and intravascular haemolysis
65
what are the two methods of erythrocyte destruction when there is mismatched transfusion
phagocytosis or lysis
66
what is autoimmune haemolytic anaemia
this is where the immune system generates antibodies and cell mediated responses against its own red blood cells which is bad as any circulating red blood cells will be targeted and destroyed
67
what is type III hypersensitivity
this involves reactions against soluble antigens or allergens circulating in the blood
antibody antigen immune complexes are deposited in tissues which leads to immune responses
68
describe type II immune complex mediated hypersensitivity
immune complexes are deposited in tissues to activate a complement which attracts neutrophils to the site
69
what are examples of type III complex mediated hypersensitivity
rheumatoid arthritis and glomerulonephritis
70
what is arthus reaction
localised hypersensitivity reaction whereby antibody antigen complexes are localised in blood vessel walls
can arise from injected particules or from inhaled or ingested allergens
71
what is serum sickness
this is a systemic form of arthus reaction where the antibody antigen complexes lodge in many different tissues
72
what is oral erythema multiforme
this is a condition characterised from blistering of the oral mucosa
there is deposition of immune complexes in the oral mucous membrane
is usually viral or drug related
73
what are the immune complexes leading to oral erythema multiforme
IgM bound immune complexes
74
describe type IV hypersenstivity
this is t cell mediated hypersensitivity that does not involve antibodies
it has a delayed response as it involves the recruitment of t cells from adaptive immunity
t cell reaction is localised at the site of antigen exposure and it involves both CD4+ and CD8+ t cells
75
how can t cells drive type IV hypersensitivity reactions
CD4+ t cells damage via macrophages - indirect
CD8+ t cells damage cells through cytotoxicity - indirect
76
summarise type IV cell mediated hypersensitivity
cytokines secreted by t helper cells activate macrophages and cytotoxic t cells
77
what are examples of type IV cell mediated hypersensitivity
contact dermatitis
diabetes mellitus type I
multiple sclerosis
78
what is tuberculosis
this is granulomas in lung tissue due to type IV hypersensitivty
79
what is an oral disease caused by type IV hypersensitivity reactions
orofacial granulomatous
80
what forms granulomas
macrophages and t cells
81
why do granulomas form
they contain infectious agents
82
what does type II lead to
complement activation and antibody dependent cell mediated cytotoxicity
83
which hypersensitivity does this describe: IgE mediated response involving mast cells, basophils and b cells that responds to an allergen or hapten
type I
84
which hypersensitivity does this describe: IgG or IgM mediated response leading to complement activation and antibody dependent cell mediated cytotoxicity
type II
85
which hypersensitivity does this describe: an antibody antigen mediated response often in vasculature but can also occur in tissues
type III
86
which type of hypersensitivty reaction causes oral erythema multiform
type III
87
which hypersensitivity does this describe: t cell mediated with no requirement for antibodies
type IV
88
which type of hypersensitivity reaction causes orofacial granulomatous
type IV
