Immunology

Question 1

What factors contribute to the skin as an immune system

Answer 1

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

Question 2

What is autoimmunity

Answer 2

When there is a reaction to host tissue

Leads to chronic inflammation

Question 3

What can activate keratinocytes

Answer 3

UV light

Sensitisers - such as in allergic contact dermatitis

Question 4

How do Langerhans cells trigger the immune response

Answer 4

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

Question 5

What do Birbeck granules look like

Answer 5

Tennis rackets

Question 6

What T cells are found in the epidermis

Answer 6

CD8+

Question 7

What T cells are found in the dermis

Answer 7

CD4+ and CD8+

Question 8

Where are T cells produces

Answer 8

Bone marrow

Question 9

How does T cell activation and antigen recognition occur

Answer 9

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

Question 10

Describe the function of Mast cells

Answer 10

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

Question 11

What are MHC proteins

Answer 11

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

Question 12

Describe MHC class 1 proteins

Answer 12

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

Question 13

Describe MHC class 2 proteins

Answer 13

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

Question 14

List 4 conditions that are associated with inappropriate immune responses

Answer 14

Psoriasis
Atopic and contact dermatitis
Bullous pemphigoid
Urticaria

Question 15

List some features of autoimmunity

Answer 15

Lymphocyte abnormality
Genetic predisposition
Hormonal influence
Anatomical alteration

Question 16

Which skin conditions are autoimmune

Answer 16

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

Question 17

What is a primary immunodeficiency

Answer 17

One of genetic causes - inherited defect

Can be specific or non-specific

Question 18

What is a secondary immunodeficiency

Answer 18

One that is acquired

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

Question 19

What mediates a Type I hypersensitivity reactions

Answer 19

IgE antibodies

Question 20

Describe how type I hypersensitivity begins

Answer 20

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

Question 21

What mediates type II and III hypersensitivity reactions

Answer 21

IgG and IgM antibodies

Question 22

Where is type II hypersensitivity significant

Answer 22

Autoimmunity and transplantation
Haemolytic disease of the newborn
Blood transfusion

Question 23

What mediates a type IV hypersensitivity reaction

Answer 23

Th1 cells

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

Question 24

Which factors affect the skins immune response

Answer 24

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

Question 25

What is the definition of hypersensitivity

Answer 25

Immune response that causes collateral damage to self | Exaggerated immune response

Question 26

What is an allergy

Answer 26

Hypersensitivity disorder of the immune system | A persons immune system reacts to normally harmless substances

Question 27

Allergy is declining in the UK true/false

Answer 27

False | It is on the increase

Question 28

Describe a type 1 allergy

Answer 28

Immediate reaction - within minutes to 2 hours | Consistent reaction with every exposure

Question 29

What is the clinical presentation of an allergy

Answer 29

Urticaria - itchy rash Angioedema Wheezing - asthma Anaphylaxis

Question 30

Describe urticaria

Answer 30

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

Question 31

What is angioedema

Answer 31

localised swelling of mucous membrane or subcutaneous tissue Face and lips

Question 32

What is anaphylaxis

Answer 32

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

Question 33

How can you investigate allergy

Answer 33

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

Question 34

What is the skin prick test

Answer 34

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

Question 35

What is the challenge test

Answer 35

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

Question 36

What is the management of allergy

Answer 36

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

Question 37

What are non-allergic reactions

Answer 37

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

Question 38

Describe type IV hypersensitivity

Answer 38

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

Question 39

How do you test for allergic contact dermatitis

Answer 39

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

Question 40

What is irritant contact dermatitis

Answer 40

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)