Introduction to Immune Response in Skin

Question 1

• What is the difference between primary and secondary skin infection?

Answer 1

Primary – when the pathogen is a direct cause of disease

Secondary – when infection results from underlying disease

Question 2

• What is the most common cause of bacterial pyoderma?

Answer 2

Staphylococcus intermedius most commonly isolated

Question 3

• If eosinophils are seen in a smear what might this suggest?

Answer 3

Underlying allergic or parasitic disease

Question 4

• What cytokines are secreted by keratinocytes in response to bacteria?

Answer 4

IL-6 & IL-8 – attract neutrophils

Question 5

• What types of leucocytes are found in the dermis and epidermis?

Answer 5

Epidermis – few macrophages and skin dendritic cells (Langerhans cells)
Dermis – macrophages, LCs and mast cells

Question 6

• What are Langerhans cells?

Answer 6

APCs, phagocytoses pathogens (similar to macrophage)

Question 7

• What is the purpose of lymph nodes?

Answer 7

LCs move to lymph node, T cells are abundant

Question 8

• What are the four types of hypersensitivity reaction?

Answer 8

Type I (immediate-mediated by IgE) – mast cells/basophils
Type II (mostly IgG mediated) – natural killer cells/macrophages
Type III (IgG/Immune complex mediated) – mast cells/neutrophils
Type IV (T cell mediated) – DCs/macrophages & T cells

Question 9

• What are the two most common immune mediated skin diseases?

Answer 9

Flea allergy dermatitis (FAD) & atopic dermatitis (AD)

Question 10

• What are the three classifications of type IV hypersensitivity?

Answer 10

Contact, tuberculin & granuloma

Question 11

• Why are there two injection sites?

Answer 11

M. avium tuberculin & M. bovis tuberculin can both give a positive result, two sites allow for a comparison – callipers are used to measure skin thickness before and 72 hours after

Question 12

• What is atopy?

Answer 12

Genetic tendency to develop allergic disease

Question 13

• What is AD tolerance associated with?

Answer 13

Anti-inflammatory cytokines TGF-β & IL-10

Question 14

• What immune response is seen in dogs with AD?

Answer 14

High IL-4 & reduced TGF-β

Question 15

• What causes FAD?

Answer 15

Flea saliva contains substances such as peptides & histamine which act as allergens

Question 16

• Which animals show the greatest reaction to flea saliva?

Answer 16

Sensitised animals intermittently exposed to fleas

Question 17

• What immune responses are present during FAD?

Answer 17

Type I & type IV hypersensitivity

Question 18

• How can FAD and AD be treated?

Answer 18

Anti-inflammatory drugs and glucocorticoids (with antibiotics)