Immunology

Question 1

What factors contribute to skin’s immunological function?

Answer 1

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

Question 2

What is hypersensitivity?

Answer 2

Immune response that causes collateral damage to self by exaggeration of normal immune mechanism

Question 3

What is autoimmunity?

Answer 3

Reaction to host tissue

Question 4

How do keratinocytes contribute to the immune response?

Answer 4

Activated by UV, sensitisers
Sense pathogens via cell surface receptors
Produce anti-microbial peptides that can kill pathogens
Produce cytokines and chemokines

Question 5

How do keratinocytes contribute to the immune response?

Answer 5

Dendritic cell (APC)
Process lipid antigens and microbial fragments and present them to effector T cells in order to activate them

Question 6

Where in the skin are CD4+ and 8+ T cells found?

Answer 6

CD8+ are in the epidermis and the dermis

CD4+ are in the dermis

Question 7

Which CD4+ helper T cells are associated with which conditions?

Answer 7

Th1 - psoriasis
Th2 - atopic dermatitis
Th17 - both

Question 8

What is the difference in action between Th1 and Th2 CD4+ T cells?

Answer 8

Th1 - activate macrophages to destroy microorganisms and release IL2, IFN gamma
Th2 - help B cells to make antibodies and release IL4, IL5 and IL6

Question 9

What is a plasmacytoid dendritic cell?

Answer 9

One that produces IFN alpha

Found in diseased skin

Question 10

What is a dermal dendritic cell?

Answer 10

One involved in antigen presenting and secreting cytokines and chemokines

Question 11

What are other examples of cells in the dermis that contribute to the immune response?

Answer 11

Macrophages
Neutrophils
Mast cells

Question 12

What are the effectors of IgE-mediated immune response?

Answer 12

Mast cells

Question 13

Which mediators do mast cells release?

Answer 13

Pre-formed: tryptase, chemise, TNF, histamine

Synthesised: interleukins, TNF, interferons, prostaglandins

Question 14

What chromosome is the MHC associated with?

Answer 14

6

Question 15

What is the function of class I MHC?

Answer 15

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

Question 16

What is the function of class II MHC?

Answer 16

Found on antigen presenting cells
Present to T helper cells
Present exogenous antigens

Question 17

What is the basic function fo MHC?

Answer 17

Control the immune response through recognition of self and non-self

Question 18

What are examples of skin conditions associated with inappropriate immune response and inflammation

Answer 18

Psoriasis

Atopic eczema

Question 19

What is the underlying pathology of psoriasis?

Answer 19

Altered tissue structure and function due to inflammation

Question 20

What are the symptoms of psoriasis?

Answer 20

Erythematous, itchy plaques on the extensors of the skin and the scalp
Nail signs
Arthritis and joint disease

Question 21

How is the immune system involved in psoriasis?

Answer 21

Keratinocytes release factors the stimulate production of IFN alpha and release interleukins and TNF
TH1 and TH17 activated
CD8+ cells activated
Dermofibroblasts release epidermal growth factors

Question 22

Which skin conditions are autoimmune?

Answer 22

Psoriasis
Vitiligo
SLE

Question 23

What is allergy?

Answer 23

An immune response to a normally harmless substance

Question 24

What is type 1 hypersensitivity?

Answer 24

Allergy

Question 25

What is the timescale of a type 1 hypersensitivity reaction?

Answer 25

Immediate (minutes to 2 hours)

Question 26

What are the routes of exposure for type 1 hypersensitivity, and examples of alleges for each?

Answer 26

Skin contact (nuts) Inhalation (pollen) Ingestion (latex) Injection (bee sting, medication)

Question 27

What is the pathophysiology of type 1 hypersensitivity?

Answer 27

Antigen binds to APC, which present to T cells Th2 cells release interleukins B cells are activated and release IgE, mast cells are activated Mast cells degranulate and release mediators

Question 28

What are the symptoms of a type 1 hypersensitivity reaction?

Answer 28

Urticaria Angioedema Wheezing Anaphylaxis

Question 29

What is urticaria?

Answer 29

Very itchy patches or erythema | Hives, wheals

Question 30

What is angioedema?

Answer 30

Localised swelling of subcutaneous tissue or mucus membranes

Question 31

What is anaphylaxis?

Answer 31

Severe, life threatening generalised or systemic hypersensitivity reaction

Question 32

In what ways does anaphylaxis affect the airways, breathing and circulation?

Answer 32

Airways - pharyngeal or laryngeal oedema Breathing - bronchospasm with tachypnoea Circulation - hypotension, tachycardia

Question 33

What are the investigations that can be done for type 1 hypersensitivity?

Answer 33

1. Specific IgE 2. Skin prick test 3. Challenge test Serum mast cell try-tase level during anaphylaxis to confirm true anaphylaxis

Question 34

What is that management for type 1 hypersensitivity?

Answer 34

``` Allergen avoidance Antihistamines (first line) Corticosteroids (second line) Adrenaline autoinjector (in anaphylaxis) Sodium chromoglycate ```

Question 35

What is the pathophysiology of type 2 hypersensitivity?

Answer 35

IgG and IgM mediated Cytotoxic Antibodies directed against cell surface antigens mediated cell destruction via complement activation

Question 36

What are examples of type 2 hypersensitivity reactions with skin manifestations?

Answer 36

Blood transfusion reactions | Autoimmune haemolytic anaemia

Question 37

What is the pathophysiology of type 3 hypersensitivity?

Answer 37

Immune complex mediated Antigen-antibody complexes deposited in various tissues induce complement activation and inflammatory response mediated by neutrophils

Question 38

What are examples of type 2 hypersensitivity reactions with skin manifestations?

Answer 38

Serum sickness Necrotising vasculitis Rheumatoid arthritis SLE

Question 39

What is the timescale for type 4 hypersensitivity?

Answer 39

Delayed - after 24-48 hours

Question 40

What are some examples of type 4 hypersensitivity reactions with skin manifestations?

Answer 40

Contact dermatitis Tubercular lesions Skin graft reactions

Question 41

What is the pathophysiology of type 4 hypersensitivity?

Answer 41

APCs present take up antigen and present to T cells Activated T cells cause apoptosis of keratinocytes and production of cytokines and chemokines Cytokines activate macrophages which mediate direct cellular damage

Question 42

What are examples of acute connect dermatitis allergens?

Answer 42

Direct skin contact - preservatives in cosmetics Airbourne contact - fragrances Injection - tattoo

Question 43

What is the clinical presentation of acute contact dermatitis?

Answer 43

Reaction in the area of skin in contact with allergen

Question 44

What is the investigation of acute contact dermatitis?

Answer 44

Patch testing

Question 45

What is irritant contact dermatitis?

Answer 45

Non-immunological process - not an allergy | Caused by contact with agents that abrade, irritate and traumatise the skin directly

Question 46

What are examples of common irritant contact dermatitis?

Answer 46

Nappy rash | Lip lick dermatitis