Immunology

Question 1

What is the difference between innate and adaptive immunity?

Answer 1

innate = non-specific, no memory 
adaptive = specific, memory

Question 2

Explain how keratinocytes in the epidermis help with immune defence?

Answer 2

produce antimicrobial peptides (directly kill pathogens) and cytokines (recruit T cells)

Question 3

Explain how langerhans cells in the epidermis help with immune defence?

Answer 3

antigen presenting cells in the prickle cell layer, characterised by the birbeck granule - pick up pathogens and present them to T cells in lymph nodes

Question 4

What are T cells and where are they produced?

Answer 4

lymphocytes made in the thymus (in the neck)

Question 5

What is the difference between CD8 T cells and CD4 T cells?

Answer 5

CD 8 = cytotoxic killer cell, found in epidermis and dermis

CD 4 - tells other cells what to do, found in the dermis

Question 6

Explain the immune defence system in the skin, from pathogen being detected to immune response?

Answer 6

• Langerhans cells are antigen presenting cells in the epidermis that pick up the bug in the skin and takes it to the nearest lymph nodes
• CD4 T cells are in charge - gets CD8 T cells to kill the bug and B cells to make antibodies against it

Question 7

Which immune cells are found in the dermis?

Answer 7

Macrophages
Neutrophils
Mast cells

Question 8

Which immune cells are found in the epidermis?

Answer 8

Langerhans cells

Keratinocytes

Question 9

What are macrophages?

Answer 9

White blood cells that eat up pathogens

Question 10

What are neutrophils?

Answer 10

White blood cells that pick up toxins

Question 11

What are mast cells?

Answer 11

effectors of IgE-mediated immune responses - release inflammatory mediators e.g. histamine

Question 12

What is the definition of hypersensitivity?

Answer 12

Exaggeration of normal immune response to something that wouldn’t usually trigger a response

Question 13

Describe the differences between type I, II, III and IV hypersensitivity reactions?

Answer 13

Type I: immediate, IgE mediated
Type II: IgG mediated, direct cell killing (cytotoxic)
Type III: immune complex mediated
Type IV: delayed, T cell mediated

Question 14

Give some examples of allergens that can trigger a type I hypersensitivity reaction?

Answer 14

Foods (nuts)
Pollen
Bee sting

Question 15

How does a type I hypersensitivity typically present?

Answer 15

urticaria
itchy skin
angioedema
anaphylaxis

Question 16

Explain the pathophysiology of a type I hypersensitivity reaction?

Answer 16

Allergen is ingested for the 1st time - IgE antibodies produced against it by B cells
Next time its ingested IgE tells mast cells to release inflammatory mediators

Question 17

What is the best investigation for a suspected type I hypersensitivity reaction to find the causative allergen?

Answer 17

Specific IgE testing

also skin prick testing and allergen challenge test

Question 18

How is a type I hypersensitivity reaction managed?

Answer 18

antihistamines 1st line
corticosteroids 2nd line
Epipen for anaphylaxis

Question 19

Give some examples of allergens that can cause a Type IV hypersensitivity reaction?

Answer 19

preservatives in cosmetics
fragrances
tattoo ink

Question 20

Explain the pathophysiology behind a type IV hypersensitivity reaction?

Answer 20

• langerhans cells go to the lymph nodes and present antigens to CD4 and CD8 T cells
• CD8 T cells directly attack “antigen” and CD4 recruit more immune cells and create a hypersensitivity reaction

Question 21

What is the best investigation for a suspected type IV hypersensitivity reaction

Answer 21

Patch testing for 48 hrs

Question 22

Management of a type IV hypersensitivity reaction?

Answer 22

Allergen avoidance
emollients/topical steroids
Rarely immunosuppressants