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Year 2 clinical pathology > Week 4 allergy > Flashcards

Week 4 allergy Flashcards

1
Q

What is the definition of Allergy & Hypersensitivity?

A

Undesirable, damaging, discomfort-producing and sometimes fatal reactions produced by the normal immune system (directed against innocuous antigens) in a pre-sensitized (immune) host.

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2
Q

Which hypersensitivity reactions are Ab mediated and which are cell mediated?

A

Types 1-3 = Ab mediated Type 4 = Cell mediated

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3
Q

What type of antibody and antigen causes type 1 hypersensitivity?

A

Ige

Exogenous

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4
Q

What is the response time and appearance of type 1 hypersensitivity?

A

15- 30 minutes reponse time

Appearance –> weal and flare

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5
Q

what is the histology of type 1 hypersensitivity? How is it transfered?

A

basophils & eosinophil

Antibodies is by how it gets transfered

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6
Q

What is another name for type 2 hypersensitivity?

A

cytotoxic

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7
Q

what is another name for type 3 hypersensitivity?

A

immune complex

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8
Q

What is the Immunopathogenesis of type 2?

A

IgM/IgG Ab response against combined self/foreign Ag at the cell surface 2) When Ab binds to Ag on solid surface get complement activation and activation of phagocytic cells, ADCC (Ab dependent cellular cytotoxicity
Cause cell damage

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9
Q

What are the clinical features of type 2? Include the histology invovled in type 2

A

Onset minutes to hours
Cell lysis and necrosis
The histology –> antibody and
complement

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10
Q

What is a common antigen that causes type 2?

A

Penicillin

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11
Q

What are associated diseases with type 2 hypersensitivity?

A

Erythroblastosis fetalis,

Goodpasture’s nephritis

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12
Q

What is Rhesus?

A

Rhesus (Rh) factor is an inherited protein found on the surface of red blood cells. If your blood has the protein, you’re Rh positive. If your blood lacks the protein, you’re Rh negative.

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13
Q

What is the immunopathalogy of type 3?

A

IgG/IgM Ab against soluble antigen- immune complex deposition

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14
Q

Clinical features of type 3?

A

Onset 3-8h
Vasculitis
Histology –> complement and
neutrophils

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15
Q

How is type 1,2,3 trasnfered?

A

Antibody

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16
Q

What sickness does type 3 hypersensitivity cause?

A

Traditional cause-serum sickness

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17
Q

What is the assoicted disease with type 3?

A

SLE

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18
Q

In type 3 hypersensitivity if the antigen entered the body via IV what would be the resulting disease and the site of immune complex deposition?

A

Diseases 1) Vasculitis 2) Nephritis 3) Arthritis Site of deposition
1) Blood vessel walls 2) Renal glomeruli 3) Joint spaces

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19
Q

In type 3 hypersensitivity if the antigen entered the body via subcutaneous route what would be the resulting disease and the site of immune complex deposition?

A

Disease - Arthus reaction

Site - Perivascular area

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20
Q

In type 3 hypersensitivity if the antigen entered the body via inhalation what would be the resulting disease and the site of immune complex

A

Disease - Farmer’s lung Site - Alveolar/Capillary interface

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21
Q

What is the difference beteen type 2 and type 3 in the interaction between antigens and antibodies?

A

Type 2 - Ab against Ag attached to a cell surface so cell lysis
Type 3 - Ab against soluble Ag so immune complex deposition

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22
Q

What is the immunopathalogy of type 4?

A

Antigen specific T-cell mediated cytotoxicity

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23
Q

what is the clinical features of type 4?

A

Delayed onset 48-72h

Apearance Erythema induration

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24
Q

What is Erythema?

A

It is superficial reddening of the skin, usually in patches, as a result of injury or irritation causing dilatation of the blood capillaries.

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25
Common antigen of type 4?
Metals-e.g nickel --> cheap metals | Tuberculin reaction
26
What is Tuberculin reaction?
Tuberculin is an extract of Mycobacterium tuberculosis that is used in skin testing in animals and humans to identify a tuberculosis infection
27
Assoicated disease with type 4?
Contact dermatitis
28
What is the process that causes type 1 hypersensitivity?
1) Barrier dysfunction - allowing entry of Ag 2) Sensitisation 3) Changes in T cell sub-sets dominated by Th2 4) IgE Ab produced 5) Allergic symptoms
29
What contributes to a person developing allergic disease?
The lack of infectious drive is a contributory factor in allergic disease
30
What are the 6 common organs invovled in allergic reaction. | Give example for each of the organs of allergic reaction
1) Eyes - allergic conjunctivitis 2) Nose - allergic rhinitis 3) Mouth - oral allergy syndrome 4) Airways - allergic asthma 5) Skin - atopic dermatitis 6) GI tract - food allergy
31
Why do we get allergies?
Those components of the immune system involved in responses to parasitic infection are also involved in allergic responses The system has developed to produce a rapid tissue-based response to re-infection
32
What is the immune response to parasitic disease?
Increased levels of IgE Total Specific to pathogen – cross-reactive Tissue inflammation with: eosinophilia & mastocytosis Basophil infiltration Presence of CD4+ T cells secreting: IL4, IL5 & IL13
33
What disease are TH1 and TH2 invovled in?
TH1 --> management of infection | Th2 --> management of allergic disease
34
Can genetic influences alone cause hypersensitivity?
NOT sufficient for disease | ONLY susceptibility, environment required
35
Can you have a hypersensitized reaction on your first time encountering the antigen?
No because you can only have a hypersensitive reaction on re-exposure to an allergen to which you have previously been exposed ie. sensitised
36
What are allergens?
Allergens are Antigens that initiate an IgE mediated response
37
What is the action of the different TH cells?
TH1 --> fight infection Th2 --> allergy response Th17 --> fights infection Treg --> calm down the pathway and block the others
38
What cytokine does TH2 produce to get B cells to produe IgE?
IL-4
39
What does production of IL-4 by TH2 do?
It signalls to B cells to produce IgE
40
What is the process of type 1 allergic response?
1) Exposure to Ag which is presented to T cells by APCs 2) T cell cytokine release resulting in Th2 delineation and B cell activation to produce IgE 3) IgE Fc portion binds to mast cell IgE receptors 4) On re-exposure allergen binds to Fab portion of mast cell bound IgE 5) Cross linking causes release of mediators from mast cells and basophils leading to symptoms
41
What 6 organs are affected in type 1 allergic response?
``` Smooth muscles blood vessels mucous gland platelet sensory nerve endings eosinophil ```
42
What is the Immunopathogenesis of IgE mediated allergic response?
IgE Ab mediated mast cell and basophil degranulation- release of preformed and de novo synthesized inflammatory mediators
43
What is the clinical features of IgE mediated allergic response?
``` Fast onset (15-30 min) Wheal and flare ```
44
Whats invovled in the late phase response to IgE mediated allergic response?
Eosinophils | Central role for Th2 T cell
45
What is the pathway of the late phase reaction in IgE mediated allergic response?
Arachidonic acid pathway --> produce leukotrienes and/or prostaglandin
46
What process is invovled in the initial phase reaction of IgE mediated allergic response?
Degranulation --> Granule contents are realeased including histamine
47
What is the role of Th2 in allergic response?
Multiple cytokine release: Innate inflammatory Response Drive for immunoglobulin production
48
What are the symptoms of RHINITIS?
Blocked nose, runny nose - often with eye symptoms
49
What can cause rhinitis?
House dust mite, animal danders, pollens
50
What is the treatment for rhinitis?
Antihistamines ( deal with immediate response) & Nasal steroids ( deal with long term symptoms)
51
What diseases are in the atopic triad?
Asthma, Rhinitis, Eczema
52
What type of hypersensitivity is each of the atopic traid diseases?
Asthma - Type 1 hypersensitivity Rhinitis - Type 1 and 3 hypersensitivity Eczema - Type 4 hypersensitivity
53
What is the two types of rhinitis? What is the frequency of rhinitis?
ALLERGIC or NON-ALLERGIC Can be perennial or seasonal
54
What is asthma?
Disease of INFLAMMATION & HYPER-REACTIVITY of small airways
55
In children what triggers asthma?
In childhood - AERO-ALLERGIC stimuli - HOUSE DUST MITE key pathogenic importance
56
What mediates asthma symptoms?
IMMEDIATE symptoms are IgE-mediated
57
What process in asthma damages the airways?
DAMAGE TO AIRWAYS due to LATE PHASE RESPONSE
58
What is the consequence of damaged airways?
DAMAGED AIRWAYS ARE HYPER-REACTIVE to non-allergic stimuli e.g. fumes
59
What two substances produced by mast cells in late phase response is key in ashtma?
Leukotrienes and Prostaglandins
60
what are the different types of dermatitis?
1) Atopic - eczema 2) Allergic - type 4 hypersensitivity 3) Non-allergic
61
How does dermatitis present clinically?
Intense itching, blistering/weeping, cracking of skin
62
What is thought to be a major cause of atopic dermatitis?
HOUSE DUST MITE
63
What is treatment for atopic dermatitis?
Topical Steroids & Moisturisers
64
What is the process in atopic dermatitis that makes people want to itch?
1) Activated T cells release a cytokine called IL31 - T cell itch mediator 2) Directly causes a scratch which leads to a cycle of barrier disruption and further exposure to hapten
65
What is Anaphylaxis?
An acute, potentially life-threatening, IgE mediated systemic hypersensitivity reaction
66
What are the different ways of diagnosing allergy?
``` History Specific IgE (>0.35 KuA/L) Skin prick test (>3mm wheal) Intra-dermal test Oral challenge test – Gold standard Basophil activation test Component resolved diagnostics ```
67
What is Basophil Activation Test?
Mix patients blood with allergen Upon cross linking basophils upregulate the expression of specific activation markers which can be detected
68
What is the advantage and disadvantage of doing specific IgE test?
Adv--> safe Dis--> False negatives False positives
69
What is the advantage and disadvantage of doing skin prick test?
Adv--> Quick Patient satisfaction Dis--> False negatives, alse positives, Antihistamines, Slight risk
70
What are the symptomatic treatment for allergic reaction?
Antihistamines, Steroids, Adrenaline
71
What is specific treatment for allergic reaction?
Specific – Immunotherapy (Subcutaneous or Sublingual
72
When is specific immunotherapy used to treat allergic reactions?
Life threatening reactions to Wasp & Bee sting Severe Hay fever Animal dander allergy
73
When is specific immunotherapy not useful in treating allergic reactions?
Multiple allergies Food allergy Allergic rashes – Eczema, Urticaria
74
What is the general idea of immunotherapy?
Trick the immune system to tolerate the antigen through controlled exposure Switch from Th2 to Th1 response W
75
What is the 6 most common food allergies?
``` COW’S MILK EGG LEGUMES - PEANUT; SOYBEAN; TREE NUTS FISH CRUSTACEANS / MOLLUSCS CEREAL GRAINS ```
76
What is the clinical manifestation of food allergy to the Gastrointestinal,Respiratory , Cutaneous system?
Gastrointestinal vomiting, diarrhoea, oral symptoms Respiratory (upper & lower) rhinitis, bronchospasm Cutaneous urticaria, angioedema role of food in atopic dermatitis unclear Anaphylaxis
77
What are the 4 common clinical manifestations of adverse reactions to food?
1) Urticaria 2) Angioedema 3) Bronchospasm 4) Anaphylaxis

Year 2 clinical pathology (21 decks)

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