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List the three physical and chemical barriers of the skin
- Stratum corneum
- Cutaneous lipids
- Antimicrobial peptides
What is the skin microbiome?
The commensal bacteria in the skin
How does the skin micro biome contribute to innate skin immunity?
It has an anti-inflammatory role and affects T cell maturation
Describe the structure of the stratum corneum
The stratum corneum consists of lipid bilayers mixed with proteins
What type of lipids are present in the stratum corneum?
Sphingolipids, free fatty acids and cholesterol
How do commensal microbes in the skin activate T cells?
They stimulate the skin and immune cells to produce IL-1 which activates T cells
What do keratinocytes produce?
Chemokines and cytokines
What is the role of chemokines and cytokines?
- Chemokines - critical in T cell and macrophage recruitment
- Cytokines - arm effector cells and direct the immune response
What is the main role of dendritic cells?
What type of dendritic cells are found in the skin?
What do mast cells release?
What is the collective term for keratinocytes, dendritic cells, mast cells and lymphocytes in the skin?
What are the three major roles of keratinocytes with regards to immunity?
- A sentinel cell active in host defence
- A pro-inflammatory effects cell
- A non-professional antigen-presenting cell
Describe the difference between the innate and adaptive skin immune response
- Innate: injury/pathogen invasion - release of primary cytokines - activation of skin cells and resident innate immune cells - Langerhans cells and dermal dendritic cells carry antigen to draining lymph node - T cells activated - more innate cells recruited
- Adaptive: pathogen / injury with recognised antigen - cytokines and chemokines released by activated Langerhans cells, fibroblasts and keratinocytes - Non-specific recruitment of CLA and effector T cells - Antigen specific T cells proliferate and destroy OR T cells no cognate antigen and it gets into general circulation via lymphatics
What type of immune cells link the innate and adaptive immune responses?
What are the primary, secondary and tertiary skin immune surveillance responses?
- 1 - innate immune system tries to trigger adaptive immune response (innate immune system ensures effective engagement of adaptive immune response)
- 2 - T cells destroy antigens they are already primed to destroy (rapid and effective local immune response to previously encountered antigens)
- 3 - If immune system finds the same antigen but in a different location it kills it anyway (enhanced adaptive response to antigens encountered in different tissues)
What is erythema with regards to the skin?
Define the following terms for epidermal response to injury a) Orthokeratotic hyperkeratosis (orthokeratosis) b) Parakeratotic hyperkeratosis (parakeratosis) c) Hypergranulosis d) Acanothosis e) Hyperplasia f) Hyper/hypopigmentation g) Lichenification
- a) Increased thickness of anuclear surface keratin
- b) Prominent granular layer often associated with orthokeratotic hyperkeratosis
- c) Thickened keratin layer that has retained nuclei
- d) Broadening of the spinous layer - often accompanies hyperplasia
- e) An increase in the number of epidermal cells, often irregular
- f) Increased/decreased pigmentation
- g) Hyperkeratosis, hyperplasia and dysplacia
What is a cutaneous callus?
Localised areas of thickening/lichenification
Where do cutaneous calluses usually develop?
Over pressure points e.g. elbow, hocks, sternum
Give examples of causes of direct/indirect traumatic skin disease
- Direct - Friction/pressure, chemical, heat, light
- Indirect - metabolic
What is a major role in the development and progression of skin disease in animals?
Which reflex often occurs in response to pruritus (or pain)?
True or false: the scratch reflex is a spinal reflex?
True, it is a spinal reflex modulated by motor cortex neurones
Describe the itch/scratch cycle
An allergen/irritant causes release of inflammatory chemicals which causes itchy, red dry skin. This causes the animal to scratch which can allow bacteria to enter the wound and further add to the skin problems and cause release of more inflammatory chemicals, and so the cycle continues.
What is acral lick dermatitis?
Hairless plaques caused by either underlying pyoderma and/or behavioural disturbances