Immunology- Hypersensitivity Flashcards by Lucy Jefford

Hypersensitivity?

Any inappropriate or excessive immune response that results in bystander damage to the self

How well did you know this?

Not at all

Perfectly

Allergy?

Immune responses are induced against innocuous exogenous antigens
Antigen specific IgE or sensitized T cells play a definite role

How well did you know this?

Not at all

Perfectly

Autoimmuinity?

A harmful immune response directed against self-antigens
This can result in damage (autoimmune disease)

How well did you know this?

Not at all

Perfectly

Type 1 hypersensitivty?

Immediate response

->usually IgE mediated

How well did you know this?

Not at all

Perfectly

What mediates type 2 hypersensitivity?

Antibody medaiated cell damage

How well did you know this?

Not at all

Perfectly

What mediates type 3 hypersensitivity?

Immune complex mediated

How well did you know this?

Not at all

Perfectly

What mediates type 4 hypersensitivity?

T cell mediated

How well did you know this?

Not at all

Perfectly

What is Type V hypersensitivty?

A variant of type 2 hypersensitivity where antibodies can stimulate a function e.g. Graves disease

How well did you know this?

Not at all

Perfectly

Give some examples of Type I hypersensitivity.

Allergies:

Asthma
Food allergy
Allergic rhinitis
Anaphylaxis

How well did you know this?

Not at all

Perfectly

What are the three phases of type I hypersensitivity?

Sensitisation
Reaction Early-Phase
Reaction Delayed-Phase

How well did you know this?

Not at all

Perfectly

What happens in sensitisation?

In some individuals, allergen exposure produces a strong T-cell response.
Antigen-presenting cells present the antigen to T-cells that produce the cytokines IL-4 and IL-13, which in turn activate B cells.
B-cells secrete IgE antibody.
The IgE binds to mast cells, sensitizing them to the allergen

->just read over x

How well did you know this?

Not at all

Perfectly

Common allergens?

Pollen
House dust mite
Animals
Latex
Peanuts

How well did you know this?

Not at all

Perfectly

What makes people more susceptible to allergens?

Atopy
Age- children more common
Family size- less common in large famillies
Smoking
Dietary factors

How well did you know this?

Not at all

Perfectly

Atopy?

Genetic predisposition to produce IgE antibody in response to environmental allergens.

How well did you know this?

Not at all

Perfectly

Which conditions does atopy increase the risks of?

Asthma
Allergic rhinitis
Eczema
Food allergy

How well did you know this?

Not at all

Perfectly

What happens in Early phase hypersensitivity?

Mast-cell degranulation occurs on subsequent exposure to the allergen
due to a specific IgE antibody–allergen interaction. This results in a cascade of biochemical events defined as the early allergic reaction,
which peaks at about 20–30 minutes

How well did you know this?

Not at all

Perfectly

What happens to the body as a result of histamine chemokines?

Vasodilation
Bronchial constriction

->can cause wheezes and wheals

How well did you know this?

Not at all

Perfectly

Treatment for someone with too much histamine?

…

Anti-histamines

How well did you know this?

Not at all

Perfectly

What happens in the late phase of hypersensivity?

Broader cell-based cascade.
2 hours after exposure and continues
over several days.
Can become chronic

How well did you know this?

Not at all

Perfectly

What are some of the investigations you can do to test for allergic disease?

Skin prick tests
Specific IgE tests
Component resolved diagnostics
Challenge tests
Mast cell tryptase
Non-specific markers for atopic state
(Total IgE, Eosinophil count)

How well did you know this?

Not at all

Perfectly

What is done in skin prick testing?

Prick skin with common allergens
Wheals will appear in response to allergens

Which type of hypersensitivity does skin prick testing test?

Type I hypersensitivity

Which type of hypersensitivity does skin patch allergen testing test?

Type IV hypersensitivity

High levels of IgE in allergen specific IgE testing in response to an allergen means what?

Allergic to the allergen

Higher IgE, more likely they are allergic

Management of allergic disease?

Avoid the allergen

Symptom management of allergic disease?

Antihistamines SABA/LAMA/SAMA inhalers in asthma Decongestants in allergic rhinitis Allergic immunotherapy

Give some examples of mast cell prevention therapies.

Leukotriene receptor antagonist Corticosteroids Mast cell stabilisers Biologics Allergen immunotherapy

Side effects of antihistamines?

Dry mouth Drowsiness Hypotension/dizziness Urinary retention

Side effects of steroids?

Immunosuppression Cushing's Osteoporosis Weight gain Neutrophilia Hyperglycaemia Hypertension

Allergen immunotherapy?

Giving the allergen in small quantities to retrain the immune system

How do you manage anaphylaxis?

ABCD Intramuscular adrenaline IV fluids

What are anaphylactoid reactions?

People who are exposed to an allergen for the first time in their life having an anaphylactic like response. Similar but different to anaphylaxis

Pathophysiology of Type II hypersensitivity?

Antibodies bind to cell-surface antigens and activates complement.

Examples of Type II hypersensitivity?

Autoimmune haemolytic anaemia Myasthenia gravis Good pastures syndrome Graves disease- sometimes considered type V Transfusion reactions e.g. rhesus, ABO

What are some of the most common causes of anaphylaxis?

Bee and wasp stings Foods Latex rubber Drugs

What is the only useful lab test in anaphylaxis?

Blood mast cell tryptase

Management of type II hypersensitivity?

Aim: removal of pathogenic antibody Plasmapheresis- removal of blood and cellular constituents are replaced combined with Immunosuppression to reduce the production of the antibody

Give an example of a localised type III hypersensitivity related condition.

Pigeon fancier's lung ->bird derived proteins are repeatedly inhaled

Give an example of a generalised type III hypersensitivity related condition.

SLE- systemic lupus erythemastosus

How are type II hypersensitivities diagnosed?

Detection of relevant antibodies in the blood Detection of immune complexes, often biopsies Surrogate markers: consumption of complement factors * ->* complement factors in the blood may decrease because they are being consumed during systemic type III hypersensitivity reactions.

Which type of hypersensitivity is the slowest to respond?

Type IV ->can take 2 or 3 days for reaction to develop, delayed hypersensitivity

Why may you want to do patch testing instead of skin pricking?

Patch testing is more suitable for type IV hypersensitivity as slower response. you check it 2-3 days after Skin prick testing is immediate response

What are haptens?

Small molecules that only elicit an immune response when attached to a larger carrier e.g. a protein. The carrier will not always cause an immune response by itself

Give some clinical examples of type IV hypersensitivity.

Contact dermatitis e.g. by poison ivy, nickel ->this is because the haptens in these materials can bind to a carrier in the body and elicit an immune response

Eczema is an immunological and dermatological condition and has some crossovers. What type of eczema is purely immunological based?

Contact allergic eczema

Eczema is an immunological and dermatological condition and has some crossovers. What type of eczema is purely dermatological based due to issues with the barrier function of the skin?

Contact irritant eczema

Eczema is an immunological and dermatological condition and has some crossovers. What type of eczema is both immunological and dermatological?

Atopic eczema

How are diagnosis's of type IV hypersensitivity conditions made?

Exposure to antigen e.g. patch testing Biopsy- avoided if can

Treatment for type IV hypersensitivity?

Avoid allergen if possible