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

Immunology - Immunology of the Skin Flashcards

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Dermatology Board Prep flashcards
1
Q

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

A

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

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2
Q

What are cytokines?

A

Proteins that are involved in cell communication

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3
Q

What are chemokines?

A

Chemical messengers that induce chemotaxis

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4
Q

What are eicosanoids?

A

Signalling molecules made by oxidation of 20-Carbon fatty acids

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5
Q

What is an antigen?

A

a protein/ peptide or polysaccharide that elicits an immune response

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6
Q

What is hypersensitivity?

A

over reaction to antigen

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7
Q

What is autoimmunity?

A

Reaction to host tissue

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8
Q

What is the stratum corneum made up of?

A

Corneocytes (terminally differentiation keratinocytes)

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9
Q

What are 3 important structural proteins in the keratin layer?

A

Filaggrin
Involucrin
Keratin

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10
Q

What is filaggrin?

A

Filament-associated protein that binds to keratin

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11
Q

What does involucrin do?

A

Contributes to formation of cell envelope that protects corneocytes

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12
Q

How do keratinocytes in the epidermis sense pathogens?

A

Via cell surface - then help mediate an immune response

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13
Q

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

A

UV

Sensitisers (e.g. contact dermatitis)

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14
Q

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

A

Anti-microbial peptides (AMPs)

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15
Q

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

A

Psoriasis

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16
Q

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

A

Cytokines and chemokines

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17
Q

Where are Langerhans cells found?

A

Interspersed with keratinocytes in the epidermis

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18
Q

What is the main skin resident immune cell?

A

Langerhans cells

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19
Q

What organelle is characteristic of Langerhans cells?

A

Birbeck granule

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20
Q

What type of immune cell are Langerhans cells?

A

Dendritic cells - antigen presenting cells

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21
Q

What shape are Birbeck granules?

A

“tennis-racket” cytoplasmic organelle

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22
Q

What do Langerhan cells do?

A

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

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23
Q

What type of T lymphocytes are located in the epidermis?

A

Mainly CD8+ (Killer) T cells

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24
Q

What type of T lymphocytes are located in the dermis?

A

CD4+ and CD8+ T cells

Other subsets of T cells are also found e.g. NK cells

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25
Q

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

A

Th1 and Th17

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26
Q

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

A

Th2 and Th17

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27
Q

What interleukin does Th17 produce?

A

Interleukin 17

28
Q

What are interleukins?

A

A group of cytokines expressed by WBCs

29
Q

Where are T cells produced?

A

Bone marrow

30
Q

Where are T cells sensitised?

A

Thymus

31
Q

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

A

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

32
Q

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

A

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

33
Q

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

A

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

34
Q

What is the purpose of CD8+ cytotoxic T cells?

A

To kill infected cells directly

Important protection against viruses and cancer

35
Q

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

A

Dermal dendritic cell

Plasmacytoid dendritic cell (pDC)

36
Q

What are dermal dendritic cells involved in?

A

Ag presenting and secreting cyto/ chemokines

37
Q

What is the purpose of plasmacytoid dendritic cells?

A

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

38
Q

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

A

Macrophages
Neutrophils
Mast cells

39
Q

What attracts circulating neutrophils to tissue?

A

Chemokines

40
Q

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

A

Mast cells

41
Q

What happens when IgE binds to mast cells?

A

Activation of the mast cell and release of inflammatory mediators

42
Q

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

A

Tryptase
Chymase
TNF
Histamine

43
Q

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

A

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

44
Q

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

A

Physical trauma, certain drugs, micro-organisms

45
Q

What chromosome is the gene for MHC found?

A

Chromosome 6

46
Q

Where are class 1 MHC found?

A

On almost all cells

47
Q

What is the purpose of class 1 MHC?

A

To present Ag to cytotoxic T cells - present endogenous Ag

48
Q

What is the purpose of class 2 MHC?

A

To present exogenous Ag to Th cells

49
Q

Where are Class 2 MHC found?

A

On APC (B cells, macrophages)

50
Q

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

A 
Skin infection
Skin tumours
Psoriasis
Atopic dermatitis
Bullous pemphigoid
Contact dermatitis
Morphea/ systemic sclerosis
Urticaria
Systemic lupus erythematous
51
Q

Give 3 examples of autoimmune skin conditions?

A

Psoriasis
Vitiligo
Systemic lupus erythematous

52
Q

What mediates type 1 hypersensitivity?

A

IgE - immediate

53
Q

What happens in type 1 hypersensitivity?

A

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
Q

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

A

Very rapid early response = minutes (wheal and flare)

Later réponse = hours (cellular infiltration, nodule)

55
Q

What mediates type 2 and 3 hypersensitivity?

A

Antibodies - IgG and IgM

56
Q

What conditions are type 2 hypersensitivity important in?

A

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

57
Q

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

A

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

58
Q

What mediates type 4 hypersensitivity?

A

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

59
Q

2 examples of a type 4 hypersensitivity reaction?

A

Tuberculin reaction

Contact allergy

60
Q

when does a type 4 hypersensitivity reaction peak?

A

24 - 48 hours after exposure

61
Q

How does ageing affect skin immunity?

A

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
Q

Non-immune cells of the epidermis?

A

Keratinocytes

Melanocytes

63
Q

Immune cells of the epidermis?

A 
Langerhans cells
T cells (Esp. CD8+ cells)
64
Q

Immune cells in the dermis?

A

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

65
Q

Non-immune cells in the dermis?

A

Fibroblasts

Lymph/ vasculature

2nd Year - Dermatology (16 decks)

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