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Dermatology > Immunology > Flashcards

Immunology Flashcards

1
Q

What factors contribute to the skin as an immune system

A

Structure - keratin layer and stratification
Cells - immune cells and keratinocytes
Cytokines, chemokines etc
Genetics

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2
Q

What is autoimmunity

A

When there is a reaction to host tissue

Leads to chronic inflammation

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3
Q

What can activate keratinocytes

A

UV light

Sensitisers - such as in allergic contact dermatitis

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4
Q

How do Langerhans cells trigger the immune response

A

The process antigens and migrate away from the epidermis to the lymph system to present them to T cells

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5
Q

What do Birbeck granules look like

A

Tennis rackets

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6
Q

What T cells are found in the epidermis

A

CD8+

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7
Q

What T cells are found in the dermis

A

CD4+ and CD8+

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8
Q

Where are T cells produces

A

Bone marrow

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9
Q

How does T cell activation and antigen recognition occur

A

Through interaction with the T cell receptor (TCR) and the Major Histocompatibility Complex (MHC)

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10
Q

Describe the function of Mast cells

A

Effectors of the IgE mediated response - allergy
IgE binding causes activation of mast cells and release of inflammatory mediators
The degranulate and release many mediators such as histamine, interleukins and TNF

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11
Q

What are MHC proteins

A

An identity tag protein that sticks out of every cell and allows the body to identify it as self
Can also show which proteins are present in the cell
If a cell lacks MHC it is attacked by the immune system

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12
Q

Describe MHC class 1 proteins

A

Found on almost all cells
Present antigens to cytotoxic T cells
Present endogenous antigens

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13
Q

Describe MHC class 2 proteins

A

Found on antigens presenting cells - B cells and macrophages
Present to Th cells
Present exogenous antigen

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14
Q

List 4 conditions that are associated with inappropriate immune responses

A

Psoriasis
Atopic and contact dermatitis
Bullous pemphigoid
Urticaria

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15
Q

List some features of autoimmunity

A

Lymphocyte abnormality
Genetic predisposition
Hormonal influence
Anatomical alteration

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16
Q

Which skin conditions are autoimmune

A

Vitiligo - melanocytes attacked by T cells
Psoriasis
SLE - autoantibodies are formed for your own DNA

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17
Q

What is a primary immunodeficiency

A

One of genetic causes - inherited defect

Can be specific or non-specific

18
Q

What is a secondary immunodeficiency

A

One that is acquired

E.g. AIDS, Ageing, cancer, malnutrition, diabetes

19
Q

What mediates a Type I hypersensitivity reactions

A

IgE antibodies

20
Q

Describe how type I hypersensitivity begins

A

Early exposure to the antigen causes the production of IgE
This binds to receptors on mast cells
On second exposure the receptors are rapidly activated and the mast cell degranulates - causing the allergic reaction

21
Q

What mediates type II and III hypersensitivity reactions

A

IgG and IgM antibodies

22
Q

Where is type II hypersensitivity significant

A

Autoimmunity and transplantation
Haemolytic disease of the newborn
Blood transfusion

23
Q

What mediates a type IV hypersensitivity reaction

A

Th1 cells

They recruit other cells to the site, hence the delayed response

24
Q

Which factors affect the skins immune response

A

Organ transplants - immunosuppressed
UV - damages structure
Ageing - change in structure, decreased effectiveness of immune system

25
Q

What is the definition of hypersensitivity

A

Immune response that causes collateral damage to self

Exaggerated immune response

26
Q

What is an allergy

A

Hypersensitivity disorder of the immune system

A persons immune system reacts to normally harmless substances

27
Q

Allergy is declining in the UK true/false

A

False

It is on the increase

28
Q

Describe a type 1 allergy

A

Immediate reaction - within minutes to 2 hours

Consistent reaction with every exposure

29
Q

What is the clinical presentation of an allergy

A

Urticaria - itchy rash
Angioedema
Wheezing - asthma
Anaphylaxis

30
Q

Describe urticaria

A

A very itchy rash
Forms hives or weals
Usually appears within one hour of allergen exposure and lasts a few hours

31
Q

What is angioedema

A

localised swelling of mucous membrane or subcutaneous tissue
Face and lips

32
Q

What is anaphylaxis

A

Life-threatening hypersensitivity reaction
Characterised by rapidly developing issues
Involves the airways closing, due to oedema, bronchospasm, hypotension, tachycardia etc

33
Q

How can you investigate allergy

A 
HISTORY!!
IgE blood test 
Skin prick test 
Patch test - for contact 
Challenge test 
Check serum mast cell tryptase levels during anaphylaxis
34
Q

What is the skin prick test

A

Introduce allergen via small needle in the skin
Cheap and quick results
Good specificity and sensitive

35
Q

What is the challenge test

A

The patient is directly exposed to the allergen
e.g. wear latex gloves or eat peanut butter
Only done in clinical setting if anaphylaxis risk is low

36
Q

What is the management of allergy

A 
Allergen avoidance
Education 
May wear alert bracelet  
Step 1 - anti-histamine 
Step 2 - corticosteroids 
Step 3 - epi-pen
37
Q

What are non-allergic reactions

A 
Non IgE mediated 
Mast cell granulation is directly caused - e.g. by drugs 
Can be metabolic - lactose 
Can be caused by toxins 
Coeliac disease
38
Q

Describe type IV hypersensitivity

A

Delayed reaction - 24-48 hours after exposure
Antigen specific
mediated by T cells
often a contact dermatitis

39
Q

How do you test for allergic contact dermatitis

A

Patch test
Common allergens are places into small discs and stuck to the back with hypoallergenic tape
Then left for 48 hours and taken off
Assess reaction after 48 and 96 hours to look for allergic reaction - positive result is a red or pink, itchy, often raised area at the site
Tells you which allergen is the cause

40
Q

What is irritant contact dermatitis

A

Not an immunological process
Contact with irritant agents causes skin irritation
Doesn’t need previous sensitisation
Examples: Nappy rash (urine) and lip lick dermatitis (saliva)

Dermatology (14 decks)

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