Skin immunology

Question 1

What is the immune function of keratinocytes?

Answer 1

Sense pathogens via cell surface receptors and help mediate an immune response

Question 2

What can activate keratinocytes?

Answer 2

UV (sunlight) and sensitizers (allergic contact dermatitis)

Question 3

What AMPs can the epidermis produce?

Answer 3

Defensins and cathelicidins

Question 4

In what disease process are AMPs in high levels?

Answer 4

Psoriasis

Question 5

What is the main immunce cell present in the epidermis?

Answer 5

Langerhans cells

Question 6

What type of cell is a langerhans cell?

Answer 6

Dendritic cell that can intersperse with keratinocytes in the epidermis

Question 7

How do langerhans cells act as immune cells?

Answer 7

They act as sentinels in the epidermis and process lipid antigens and microbial fragments and present them to effector T cells to activate them
They have birbeck granules

Question 8

Where can T cells be found in the skin?

Answer 8

In high numbers in the epidermis and dermis

Question 9

What type of T cell is found in the epidermis?

Answer 9

CD8+ cells

Question 10

What type of T cell is found in the dermis?

Answer 10

CD4+ and CD8+ cells

Question 11

What is Th1 associated with?

Answer 11

Psoariasis

Question 12

What is TH2 associated with?

Answer 12

Atopic dermatitis

Question 13

What is TH17 associated with?

Answer 13

Psoriasis and atopic dermatitis

Question 14

Where are T cells produced?

Answer 14

Bone marrow and sensitised in the thymus

Question 15

What does Th1 do?

Answer 15

Activates macrophages to destroy microorganisms and produces IL2 and IFN-gamma

Question 16

What does TH2 do?

Answer 16

Helps B cells make antibodies

Producecs IL4, IL5 and IL^

Question 17

What do CD8+ cells do?

Answer 17

Kill infected cells directly

Protect against viruses and cancer

Question 18

What dendritic cells are found within the dermis?

Answer 18

Dermal dendiritc cell

Plasmacytoid dendritic cell

Question 19

What is the function of dermal DC?

Answer 19

Involved in antigen presentation and secreting cytokines and chemokines

Question 20

What is the function of plasmacytoid DC?

Answer 20

To produce IFN-alpha

Found in diseased skin

Question 21

What immune cells are found in the dermis?

Answer 21

Macrophages, neutrophils, mast cells

Question 22

What is the function of neutrophils?

Answer 22

Circulating leukocytes attracted to tissue by chemokines

Question 23

What is the function of mast cells?

Answer 23

Tend to be found in barriers
Effectors of IgE mediated immune response (allergy)
Binding of IgE causes activation of the mast cell and release of inflammatory mediators

Question 24

Where are MHC1 found?

Answer 24

On all cells

Present antigens to cytotoxic T cells

Question 25

What is an endogenous Ag?

Answer 25

Endogenous antigens are generated within normal cells as a result of normal cell metabolism, or because of viral or intracellular bacterial infection. The fragments are then presented on the cell surface in the complex with MHC class I molecules.

Question 26

Where are MHC2 found?

Answer 26

Found on antigen presenting cells (B cells and macrophages) | Present to Th cells

Question 27

What is an exogenous Ag?

Answer 27

By endocytosis or phagocytosis, exogenous antigens are taken into the antigen-presenting cells (APCs) and processed into fragments. APCs then present the fragments to T helper cells (CD4+) by the use of class II histocompatibility molecules on their surface

Question 28

What chromosome codes for MHC molecules?

Answer 28

Chromosome 6

Question 29

What skin conditions are associated with an inappropriate immune response/ inflammation?

Answer 29

``` Psoriasis Atopic dermatitis Bullous pemphigoid Contact dermatitis Morphea Urticaria SLE Skin infections Skin tumours ```

Question 30

What is the hallmark of psoriasis?

Answer 30

Inflammation | There is a non-ending accelerated phase 2 wound response

Question 31

What skin appendages can psoriasis affect?

Answer 31

Nails and joints

Question 32

What are the symptoms of psoriasis?

Answer 32

Erythema Itchy plaques Bleeding of lesions Arthritis

Question 33

What can cause the onset or exacerbation of psoriasis?

Answer 33

``` Bacterial pharyngitis (gram +ve) Mild trauma of skin (koebner phenomenom) HIV infection Stress B-blockers or lithium Genetic ```

Question 34

What is the immunopathogenesis of psoriasis?

Answer 34

KC under stress releases factors to produce IFN-alpha Chemical signals activate DC which migrate to skin draining lymph nodes to present to and activate T cells Th1 and Th17 T cells attracted to dermis by chemokiles where they secrete interleukins causing KC proliferation, AMP release and neurtrophil attracting chemokines

Question 35

How can atopic eczema occur?

Answer 35

Mutations in filaggrin gene Decrease in AMP in skin T cells (Th2), DC, KC, macrophages and mast cells are involved

Question 36

What skin conditions are autoimmune?

Answer 36

Psoriasis Vitiligo SLE - fault apoptosis causing lots of DNA to accumulate in the blood and therefore the body starts to form auto-antibodies to its own DNA

Question 37

What is type 1 hypersensitivity?

Answer 37

Antibody mediated IgE

Question 38

What is the pathogenesis of type 1 hypersensitivity?

Answer 38

Early exposure to allergen causes the production of IgE which binds to the IgE receptor on mast cell. Later exposure causes rapid crosslinking of the receptors, signal transduction and degranulation of the mast cell

Question 39

What is type 2 hypersensitivity?

Answer 39

Antibody mediated: IgG and IgM | Important in autoimmunity and transplantation

Question 40

What are some common disaeses via type 2 hypersensitivity?

Answer 40

Haemolytic disease of the newborn | Blood transfusion recipients

Question 41

What is type 4 hypersensitvity?

Answer 41

Cell mediated: Th1 | Delayed type hypersensitivity is based on T-cell mediated response

Question 42

What are some examples of type 4 hypersensitivity reactions?

Answer 42

Tuberculin reaction Contact allergy Metals - nickel and chromate

Question 43

What cell types are involved in skin immunity in the epidermis?

Answer 43

Keratinocytes Langerhans CD8+ T cells Melanocytes

Question 44

What cell types are involved in skin immunity in the dermis?

Answer 44

``` DC cells Macrophages CD4+ and CD8+ T cells NK cells Fibroblasts Lymph/ vasculature ```