Immunology - Immunology of the Skin Flashcards Preview

2nd Year - Dermatology > Immunology - Immunology of the Skin > Flashcards

Flashcards in Immunology - Immunology of the Skin Deck (65):
1

What 4 factors contribute to the skin as an immunological system?

Genetics
Structure (keratin layer, stratification)
Cell types (immune cells, keratinocytes)
Chemical signals/ molecules (cytokines, chemokines, eicoanoids, antimicrobial peptides

2

What are cytokines?

Proteins that are involved in cell communication

3

What are chemokines?

Chemical messengers that induce chemotaxis

4

What are eicosanoids?

Signalling molecules made by oxidation of 20-Carbon fatty acids

5

What is an antigen?

a protein/ peptide or polysaccharide that elicits an immune response

6

What is hypersensitivity?

over reaction to antigen

7

What is autoimmunity?

Reaction to host tissue

8

What is the stratum corneum made up of?

Corneocytes (terminally differentiation keratinocytes)

9

What are 3 important structural proteins in the keratin layer?

Filaggrin
Involucrin
Keratin

10

What is filaggrin?

Filament-associated protein that binds to keratin

11

What does involucrin do?

Contributes to formation of cell envelope that protects corneocytes

12

How do keratinocytes in the epidermis sense pathogens?

Via cell surface - then help mediate an immune response

13

What 2 things (other than pathogens) can activate keratinocytes in the epidermis leading to an immune response?

UV
Sensitisers (e.g. contact dermatitis)

14

What can keratinocytes in the epidermis produce that can kill pathogens directly?

Anti-microbial peptides (AMPs)

15

In what condition are AMPs found in high levels in the skin?

Psoriasis

16

What do keratinocytes in the epidermis produce that recruit and regulate cells of the adaptive and innate immune system?

Cytokines and chemokines

17

Where are Langerhans cells found?

Interspersed with keratinocytes in the epidermis

18

What is the main skin resident immune cell?

Langerhans cells

19

What organelle is characteristic of Langerhans cells?

Birbeck granule

20

What type of immune cell are Langerhans cells?

Dendritic cells - antigen presenting cells

21

What shape are Birbeck granules?

"tennis-racket" cytoplasmic organelle

22

What do Langerhan cells do?

"Keep watch" in the epidermis
Process lipid Ag and microbial fragments and present them to effector T cells
Help to activate T cells

23

What type of T lymphocytes are located in the epidermis?

Mainly CD8+ (Killer) T cells

24

What type of T lymphocytes are located in the dermis?

CD4+ and CD8+ T cells
Other subsets of T cells are also found e.g. NK cells

25

What type of CD4+ Th cells are associated with psoriasis?

Th1 and Th17

26

What type of CD4+ Th cells are associated with atopic dermatitis?

Th2 and Th17

27

What interleukin does Th17 produce?

Interleukin 17

28

What are interleukins?

A group of cytokines expressed by WBCs

29

Where are T cells produced?

Bone marrow

30

Where are T cells sensitised?

Thymus

31

What does Ag recognition and T cell activation involve integration with?

T cell receptor (TCR) and major histocompatibility complex (MHC) - this is enhanced by co-receptors

32

What do Th1 T cells do? what do they release (2)?

Activate macrophages to destroy micro-organisms - release IL2 and IFNgamma

33

What do Th2 cells do? What do they release (3)?

Help B cells to make Ab, release IL4, IL5 and IL6

34

What is the purpose of CD8+ cytotoxic T cells?

To kill infected cells directly
Important protection against viruses and cancer

35

What are 2 examples of dendritic cells found in the dermis?

Dermal dendritic cell
Plasmacytoid dendritic cell (pDC)

36

What are dermal dendritic cells involved in?

Ag presenting and secreting cyto/ chemokines

37

What is the purpose of plasmacytoid dendritic cells?

Ag presenting and to produce IFNalpha -> found in diseased skin

38

Apart from dendritic cells, what 3 other immune cells are present in the dermis?

Macrophages
Neutrophils
Mast cells

39

What attracts circulating neutrophils to tissue?

Chemokines

40

What cells are the effects of IgE-mediated immune response?

Mast cells

41

What happens when IgE binds to mast cells?

Activation of the mast cell and release of inflammatory mediators

42

What are 4 examples of pre-formed mediators released from mast cells?

Tryptase
Chymase
TNF
Histamine

43

What are examples of newly synthesised mediators released from mast cells?

IL (3, 5, 6, 8, 13, 16, 18), TNF, TGFbeta, PGD2, PGE2, LTB4, LTC4, VEGF, bFGF, IP-10, MIP-1alpha, MIP-1beta

44

Apart from IgE, what else can activate mast cells? (3)

Physical trauma, certain drugs, micro-organisms

45

What chromosome is the gene for MHC found?

Chromosome 6

46

Where are class 1 MHC found?

On almost all cells

47

What is the purpose of class 1 MHC?

To present Ag to cytotoxic T cells - present endogenous Ag

48

What is the purpose of class 2 MHC?

To present exogenous Ag to Th cells

49

Where are Class 2 MHC found?

On APC (B cells, macrophages)

50

Skin conditions associated with inappropriate immune response/ inflammation? (9)

Skin infection
Skin tumours
Psoriasis
Atopic dermatitis
Bullous pemphigoid
Contact dermatitis
Morphea/ systemic sclerosis
Urticaria
Systemic lupus erythematous

51

Give 3 examples of autoimmune skin conditions?

Psoriasis
Vitiligo
Systemic lupus erythematous

52

What mediates type 1 hypersensitivity?

IgE - immediate

53

What happens in type 1 hypersensitivity?

Early exposure to allergen causes the production of IgE, which binds to FceRI receptor on mast cells
Laster exposure causes rapid cross linking of the receptors, signal transduction and degranulation of mast cell

54

What 2 time frames of responses are involved in type 1 hypersensitivity?

Very rapid early response = minutes (wheal and flare)
Later réponse = hours (cellular infiltration, nodule)

55

What mediates type 2 and 3 hypersensitivity?

Antibodies - IgG and IgM

56

What conditions are type 2 hypersensitivity important in?

Auto-immunity and transplantation e.g. haemolytic disease the newborn

57

What type of reaction does skin testing in type 3 hypersensitivity lead to?

Arthus reaction- slow than type 1 but faster than type 4

58

What mediates type 4 hypersensitivity?

Th1 cells - delayed type hypersensitivity based on a t cell resoles which then recruits other cells to the site

59

2 examples of a type 4 hypersensitivity reaction?

Tuberculin reaction
Contact allergy

60

when does a type 4 hypersensitivity reaction peak?

24 - 48 hours after exposure

61

How does ageing affect skin immunity?

Changes in skin structure = easier access
Decreased ability to detect malignant cells
Decreased ability to detect Ag = infection risk
Decreased ability to detect self from non-self = autoimmunity

62

Non-immune cells of the epidermis?

Keratinocytes
Melanocytes

63

Immune cells of the epidermis?

Langerhans cells
T cells (Esp. CD8+ cells)

64

Immune cells in the dermis?

Dendritic cells
Macrophages
NK cells
T cells (CD4+ and CD8+)

65

Non-immune cells in the dermis?

Fibroblasts
Lymph/ vasculature