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Dermatology > Immunology/Biochem of Skin > Flashcards

Immunology/Biochem of Skin Flashcards

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Dermatology Board Prep flashcards
1
Q

How does the structure of skin contribute to its function as an immunological system?

A

Keratin layer (stratum corneum), stratifications

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2
Q

What cell types are involved in the immune response in the skin?

A

Immune system cells, keratinocytes

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3
Q

What are some examples of chemical signals/molecules that influence cell behaviour or help target pathogens?

A

Cytokines, chemokines, eicosanoids, antimicrobial peptides

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4
Q

What are the different immune responses?

A

Normal (innate and adaptive), hypersensitivity, immunodeficiency, autoimmunity

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5
Q

What occurs in hypersensitivity?

A

Over-reaction to antigen

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6
Q

What occurs in immunodeficiency?

A

Infection not controlled (tumours may form)

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7
Q

What occurs in autoimmunity?

A

Reaction to host (chronic inflammation)

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8
Q

How is the keratin layer of the skin formed?

A

Terminal differentiation of keratinocytes to corneocytes

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9
Q

What are some important proteins in the keratin layer?

A

Filaggrin, keratin and involucrin

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10
Q

What is another name for the keratin layer?

A

Stratum corneum

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11
Q

What are keratinocytes?

A

Structural and functional cells of the epidermis

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12
Q

How are keratinocytes involved in the immune response?

A

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

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13
Q

What are some examples of things which can activate keratinocytes?

A

UV and sensitisers (e.g allergic contact dermatitis)

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14
Q

What do keratinocytes produce that aids in the immune response?

A

Antimicrobial peptides (AMP), cytokines, chemokines

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15
Q

What do AMPs do?

A

Directly kill pathogens

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16
Q

What do cytokines and chemokines do?

A

Recruit and regulate cells of the adaptive and innate immune system

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17
Q

In what skin condition are high levels of AMP found in the skin?

A

Psoriasis

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18
Q

What are Langerhans cells?

A

Type of dendritic cell that intersperse with the keratinocytes in the epidermis

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19
Q

What are the main skin-resident immune cells?

A

Langerhans cells

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20
Q

How do Langerhans cells work?

A

Antigen presenting cells (APCs) that process lipid antigen and microbial fragments and present them to effector T cells (help activate T cells)

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21
Q

What are Langerhans characterised by, and what do they act as in the skin?

A

Birbeck granules; act as sentinels

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22
Q

Where are T cells found in healthy skin

A

Both the epidermis and dermis

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23
Q

What kind of T cells are found in the epidermis?

A

Mainly CD8+ T cells

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24
Q

What kinds of T cells are found in the dermis?

A

CD4+ and CD8+ T cells

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25
Q

What other kind of T cells can be found in the epidermis and dermis?

A

Natural killer cells

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26
Q

What are some CD4+ Th cells associated with inflammation of the skin?

A

Th1 (psoriasis), Th2 (atopic dermatitis), Th17 (psoriasis and atopic dermatitis)

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27
Q

Where are T cells produced and synthesised?

A

Produced in the bone marrow and synthesised in the thymus

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28
Q

What cells form the basis of cell-mediated immunity?

A

T cells

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29
Q

What are involved in antigen recognition and T cell activation?

A

Interaction between the T cell receptor and the Major Histocompatibility complex (MHC), enhanced by co-receptors (CD4+ and CD8+)

30
Q

What are the two CD4+ helper cells?

A

Th1 and Th2

31
Q

How does Th1 work?

A

Activate macrophages to destroy micro-organisms (e.g IL-2, IFNg)

32
Q

How does Th2 work?

A

Helps B cells make antibodies (e.g IL-4/5/6)

33
Q

How do CD8+ cytotoxic T cells work?

A

Ca kill cells directly (important in protection against viruses and cancer)

34
Q

What are some dermal dendritic cells?

A

Dermal dendritic cells (involved in antigen presenting and secretion of chemo/cytokines), Plasmacytoid dendritic cells (produce IFNa, found in diseased skin)

35
Q

How do cytokines and chemokines work during the inflammatory response?

A

Modulate the response and recruit/activate different cell types to the locus

36
Q

What are other cells involved in the immune response found in the dermis?

A

Macrophages, Neutrophils, Mast cells

37
Q

What are neutrophils?

A

Circulating leukocytes attracted to tissue by chemokines

38
Q

Where do mast cells tend to be found?

A

In “barriers”

39
Q

What are mast cells?

A

Effector cells of the IgE-mediated immune response (allergy)

40
Q

How are mast cells activated and what does this cause?

A

IgE binds causing activation and release of inflammatory mediators

41
Q

What else can activate mast cells?

A

Trauma, some drugs, certain micro-organisms

42
Q

What are some preformed mediators of inflammation found in mast cells?

A

Tryptase, chymase, TNF, histamine

43
Q

What are some inflammatory mediators that are newly synthesised by mast cells?

A

IL-3/5/6/8, TNF, TGFb, IFNy, PGD2

44
Q

What chromosome is linked to MHC molecules?

A

Chromosome 6

45
Q

What is MHC class I?

A

Found on almost all cells, presents endogenous antigen to CD8+ T cells

46
Q

What is MHC class II?

A

Found on antigen presenting cells (B cells, macrophages), presents exogenous antigen to Th cells (CD4+)

47
Q

How does MHC control the immune system?

A

Through recognition of “self” and “non-self”

48
Q

What are some skin conditions linked to an inappropriate immune response?

A

Psoriasis, Atopic dermatitis, Bullous pemphigoid, Contact dermatitis, Morphea/systemic sclerosis, Urticaria, SLE, Skin tumours

49
Q

How is psoriasis triggered?

A

Environmental factors in genetically susceptible individuals

50
Q

What is the hallmark of skin lesions in psoriasis?

A

Inflammation

51
Q

Are the plaques in psoriasis reversible?

A

Yes

52
Q

What do keratinocytes release when they are under stress in psoriasis?

A

Factors that stimulate plasmacytoid dendritic cells and produce IFNa, release IL-1b/6 and TNF

53
Q

Where do the dendritic cells migrate to in psoriasis once activated?

A

Skin draining lymph nodes-present to and activate T cells (Th1 and Th7)

54
Q

Where are T cells attracted to in psoriasis?

A

Attracted to dermis by chemokines and then secrete IL-17A/17F/22 (stimulates keratinocyte proliferation, AMP release and neutrophil-attracting chemokines)

55
Q

How is atopic eczema different from psoriasis?

A

Histologically different, non-lesioning skin is not normal

56
Q

Why does atopic eczema occur?

A

Impairment of skin barrier-mutations in filaggrin gene associated with severe/early onset, decreased AMP in skin

57
Q

What cells are involved in atopic eczema?

A

T cells (Th2), dendritic cells, keratinocytes, macrophages and mast cells (all found in lesions)

58
Q

How does the defective skin barrier in atopic eczema cause disease?

A

Allows access/sensitisation to allergen and promotes colonisation by micro-organisms

59
Q

What are some factors in autoimmunity?

A

Lymphocyte abnormalities, intercell communication, genetic predisposition, anatomic abnormalities, hormonal influence, infection

60
Q

What are some diseases caused by autoimmunity?

A

Psoriasis, vitiligo, systemic lupus erythematous

61
Q

What are the two kinds of immunodeficiency?

A

Primary (genetic)-inherited defect (specific/non-specific)

Secondary (acquired)-AIDS, malignancy, aging, diabetes

62
Q

What mediates a type 1 hypersensitivity reaction?

A

IgE

63
Q

How do allergies arise?

A

Early exposure to allergen causes production of IgE which binds to FceR1 receptor on mast cells

64
Q

What occurs on later exposure to an antigen in allergy?

A

Rapid cross-linking of receptors, signal transduction and degranulation of the mast cell

65
Q

How long can an allergic response take?

A

Minutes (very early onset, Wheal and flare), hours (cellular infiltration nodule)

66
Q

What is a type II hypersensitivity mechanism important in?

A

Autoimmunity and transplantation (haemolytic disease)

67
Q

What occurs in skin testing for a type III hypersensitivity response?

A

Leads to Arthus reaction (slower than type I skin response but faster that type IV response)

68
Q

What mediates type II and III hypersensitivity responses?

A

IgG and IgM

69
Q

What mediates type IV hypersensitivity responses?

A

Th1-based on T-cell mediated response which then recruits other cells to site (tuberculin reaction)

70
Q

When does a type IV hypersensitivity reaction peak?

A

24-48 hrs after contact with allergen

71
Q

What cells are found in the epidermis of the skin?

A

Keratinocytes, Langerhans cells, CD8+ T cells, melanocytes

72
Q

What cells are found in the dermis of the skin?

A

Dendritic cells, macrophages CD4+ and CD8+ T cells, natural killer cells, fibroblasts, lymph/vasculature

Dermatology (31 decks)

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