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LR Dermatology > Skin Immunology > Flashcards

Skin Immunology Flashcards

(47 cards)

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1
Q

What factors contribute to the skin’s immune system?

A
  • Physical barrier (corneocytes in the keratin layer)

- Innate and adaptive immune cells

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2
Q

What are the key immune cells in the epidermis?

A
  • Keratinocytes

- Langerhans cells

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3
Q

How do keratinocytes aid the skin’s immune system (3)?

A
  • Sense pathogens via cell surface receptors and trigger an inflammatory response
  • Produce antimicrobial peptides (AMPs) that can directly kill pathogens
  • Produce cytokines and chemokines to recruit and regulate immune cells at the site
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4
Q

What are Langerhans cells?

A

A type of dendritic (antigen presenting) cell interspersed with keratinocytes in the epidermis

They are the main skin resident immune cell

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5
Q

How do Langerhans cells aid in the skin’s immune system?

A

They survey the environment with their dendrites, bind pathogens, and travel to lymph nodes to present the pathogens antigens to effector T cells

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6
Q

Which immune cells are found in both the dermis and epidermis?

A

T cells (mainly CD8+ cells in the epidermis)

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7
Q

Which immune cells are found in the dermis?

A

Dendritic cells, macrophages, T cells, natural killer cells, neutrophils, mast cells

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8
Q

How do CD4+ cells (helper T cells) aid in the skin’s immune system?

A

Th1: bind MHC II and produce cytokines that activate macrophages to destroy pathogens

Th2: bind MHC II and activate B cells to produce specific antibodies

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9
Q

How do CD8+ cells (cytotoxic T lymphocytes) aid in the skin’s immune system?

A

Bind MHC I and Fas death receptors, directly killing affected cells via apoptosis
(this is useful for infected cells or tumour cells)

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10
Q

How do neutrophils aid in the skin’s immune system?

A

They are the first responders to infection and attach pathogens by phagocytosis and degranulation of toxic substances

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11
Q

How do macrophages aid in the skin’s immune system?

A

Phagocytose pathogens and recruit more neutrophils to the site

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12
Q

How do mast cells aid in the skin’s immune system?

A

They are activated in response to IgE binding (allergic response), resulting in release of granules containing pro-inflammatory mediators

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13
Q

How do natural killer cells aid in the skin’s immune system?

A

They are activated by the release of interferons or other cytokines by macrophages

They bind MHC I and induce apoptosis

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14
Q

How does organ transplant damage the skin’s immune response?

A

Immunosuppressive treatments

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15
Q

How does sunlight damage the skin’s immune response?

A
  • Suppresses the immune system

- Damages skin structure

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16
Q

How does ageing damage the skin’s immune response?

A
  • Changes to skin structure
  • Decreased ability to detect malignant cells and foreign antigens
  • Decreased ability to recognise self from non-self (autoimmunity)
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17
Q

What are Birbeck granules?

A

Rod-shaped granules exclusive to epidermal langerhans cells

Their function is unknown

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18
Q

Which T helper cells are associated with psoriasis?

A

Th1 and Th17

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19
Q

Which T helper cells are associated with atopic eczema/dermatitis?

20
Q

The epidermis contains mainly CD4+ T cells. True/false

Study These Flashcards
A

False

Epidermis mainly contains CD8+ T cells

21
Q

What is the function of Th1 cells?

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A

Activate macrophages to eliminate pathogens

22
Q

What is the function of Th2 cells?

Study These Flashcards
A

Help B cells make antibodies

23
Q

Type 1 allergy is mediated by…

24
Q

How soon after exposure does a type 1 allergic reaction occur?

Study These Flashcards
A

Within minutes -> up to 2 hours

25
Type 1 allergies don't always occur with every exposure. True/false?
False Type 1 allergies have a reproducible reaction with every exposure. Intolerance is more likely if reactions do not occur with every exposure
26
What are the 4 routes of exposure for type 1 allergy?
Ingestion (e.g., nuts, seafood) Inhalation (e.g., pollen) Skin contact (e.g., latex) Injection (e.g., bee sting)
27
Describe the mechanisms involved in a type 1 allergic reaction to peanuts
Sensitisation: - Peanut proteins taken up by dendritic cells - DC's present antigen to T cells - Th2 secretes cytokines to activate B cells - B cells produce antibodies for peanut allergen - IgE bind to mast cells Allergic reaction: - IgE re-encounters peanut antigen - IgE causes release of mediators from the mast cell they are bound to - These cause the allergic reaction
28
What are the signs and symptoms of a type 1 allergic reaction?
Urticaria (raised, itchy rash on the skin) Angioedema Rhinorrhoea/sneezing Wheeze Abdominal pain Nausea/vomiting Diarrhoea
29
What are the signs and symptoms of anaphylaxis?
Urticaria, flushing, angioedema, throat tightening, SOB, wheeze, hypotension, tachycardia, chest pain, fainting, abdominal pain, nauseam vomiting
30
List investigations involved in suspected type 1 allergy
- History (most important) - Specific IgE testing (RAST) - Skin prick test - Challenge test - Serum mast cell tryptase level (during anaphylaxis)
31
What are the advantages and disadvantages of skin prick testing?
Advantages: - Quick (results in 15-20mins) and cheap - Higher specificity & sensitivity than IgE testing (90+% compared to 70-75%) Disadvantages: - Anaphylaxis risk
32
How is challenge testing carried out to avoid anaphylaxis?
The allergen is presented a little bit at a time e.g., touch lips -> chew and spit -> swallow
33
Why would you carry out challenge testing for type 1 allergy?
If the skin prick test came back negative
34
What is the gold standard management for type 1 allergy?
Allergen avoidance
35
What is the step-up management plan for a patient with a type 1 allergy?
- Anti-histamines - Anti-inflammatory e.g., corticosteroid (if antihistamine doesn't work within 30 mins) - Adrenaline autoinjector (for anaphylaxis)
36
What dose of pre-loaded adrenaline is given to... - adults - children ... from an epi-pen?
Adults - 300 micrograms | Children - 150 micrograms
37
List some non-allergic reactions that can mimic the symptoms of a type 1 allergic reaction
- Coeliac disease - Esosinophilic gastroenteritis - Use of morphine/aspirin/NSAIDs - Lactose intolerance - Scombroid fish toxin
38
Type 4 allergy is mediated by...
T cells
39
Type 4 allergic reactions of the skin are called...
*Allergic contact dermatitis*/ allergic contact allergy
40
How soon after exposure does a type 4 allergic reaction occur?
After 12-24 hours
41
What are the 3 main routes of exposure for allergic contact dermatitis?
Direct skin contact (e.g., preservatives in makeup) Airborne contact (e.g., perfume, plants) Injection (e.g., tattoo)
42
Describe the sensitisation phase of allergic contact dermatitis
- Allergen penetrates the epidermis and is taken up by Langerhan cells - These migrate to lymph nodes and present the antigen to CD4+ and CD8+ cells - These T cells clonally expand in the lymph nodes then travel through the blood to affected tissues
43
Describe the elicitation phase of allergic contact dermatitis
- On re-exposure, APC's present the antigen to antigen-specific T cells - T cells are activated and recruit more T cells - T cella release chemokine and cytokines that lead to the reaction seen in allergic contact dermatitis
44
What is the gold-standard test for allergic contact dermatitis?
Patch testing
45
What are the steps of Patch testing for allergic contact dermatitis?
- Allergens are prepared on Finn chambers - Finn chambers are applied to the back - Chambers are removed after 48 hours - Readings are taken at days 2 and 4 (48 and 96 hours)
46
What factors, other than allergic, can cause dermatitis?
- Irritant contact e.g., abrasion causing nappy rash - Endogenous factors from underlying skin disorder e.g., dry eczema, scaly psoriasis - Infection
47
What are the management options for allergic contact dermatitis?
- Allergen avoidance/ minimisation - Emollients (moisturiser) - Topical steroids - UV phototherapy - Immunosuppressants (not used often)

LR Dermatology (11 decks)

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