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Dermatology > Immunology > Flashcards

Immunology Flashcards

1
Q

Name factors that contribute to skin as an immunological system

A
  • structure; keratin layer (stratum corneum), stratification
  • cell types; immune system cells and keratinocytes
  • cytokines, chemokines, eicosanoids, antimicrobial peptides; chemical signals / molecules that influence cell behaviour or help target pathogens
  • genetics
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2
Q

Describe the keratin layer

A
  • tough, lipid rich, physical barrier
  • formed by terminal differentiation of keratinocytes to corneocytes
  • also known as the stratum corneum
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3
Q

Name important structural proteins in the keratin layer and epidermis

A
  • filaggrin
  • involucrin
  • keratin
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4
Q

Describe the keratinocytes in the epidermis

A
  • structural and functional cells of the epidermis
  • sense pathogens via cell surface receptors and help mediate an immune response
  • produce antimicrobial peptides that can directly kill pathogens
  • produce cytokines and chemokines
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5
Q

What have been found at high levels in patients with psoriasis?

A

Antimicrobial peptides (AMPs)

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6
Q

Describe the langerhans cells in the epidermis

A
  • a type of dendritic cell that intersperse with keratinocytes in the epidermis
  • the main skin resident immune cells
  • they are antigen presenting cells, characterised by the birbeck granule
  • act as sentinels in the epidermiis
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7
Q

What is involucrin?

A

A structural protein that also helps to form the so called cornified envelope in the outer dermis. Helps to from structural cohesive to shield from microbes

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8
Q

Describe the T cells in the epidermis and dermis

A
  • healthy skin contains a large number of t lymphocytes in both the epidermis and dermis
  • mainly cd8 t cells in the epidermis
  • cd4 and cd8 ells are in the dermis
  • other subsets of T cells eg natural killer cells are also found
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9
Q

TH1 cells are associated with which condition?

A

Psoriasis

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10
Q

TH2 cells are associated with which condition?

A

Atopic dermatitis

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11
Q

TH17 cells are associated with which condition?

A

Psoriasis and atopic dermatitis

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12
Q

Describe dendritic cells in the dermis

A
  • dermal DC; involved in Ag presenting and secreting cyto and chemokines
  • plasmacytoid DC; produce INFalpha, found in diseased skin
  • APCs; transmit information to T and B cells
  • secrete cyto / chemokines during the inflammatory response
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13
Q

Name some skin conditions associated with inappropriate immune response / inflammation

A
  • psoriasis
  • atopic dermatitis
  • bullous pemphigoid
  • contact dermatitis
  • morphea / systemic sclerosis
  • urticaria
  • systemic lupus erythematosus
  • skin infections
  • skin tumours
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14
Q

Name the four types of immunological hypersensitivity

A
  1. immediate reactions mediated by IgE and mast cells
  2. cytotoxic reactions mediated by IgG and IgM antibodies and complement
  3. arthus reaction / immune complex mediated disease
  4. delayed / cell mediated reactions, involving lymphocytes and lymphokines
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15
Q

What two types of hypersensitivity are seen in the skin?

A

Type 1 and type 4

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16
Q

Describe the process of type 1 hypersensitivity

A
  • IgE antibody in cell surface passively sensitises the cell
  • antigen binds directly to antibody and activates cell membrane
  • release of histamine, heparin, other chemotactic factors (ECF, NCF), PAF, leukotrienes and prostaglandins
17
Q

Name some cutaneous examples of type 1 hypersensitivity

A
  • urticaria
  • angio oedema
  • anaphylaxis
18
Q

Describe urticaria

A
  • red wheals develop

- resembling in nettle rash, caused by dilated blood vessels and leakage of fluid into surrounding tissue

19
Q

Describe angio-oedema

A
  • a deeper cutaneous reaction than urticaria

- causing swelling of sub-cutaneous tissues, including mucous membranes eg lips

20
Q

Describe anaphylaxis

A
  • life threatening generalised reaction, with urticaria a/o angio-oedema, laryngeal (throat) swelling, bronchospasm (narrowed airways in lungs), hypotension or shock (drop in blood pressure)
21
Q

Name some cutaneous examples of type 4 hypersensitivity

A
  • allergic contact dermatitis
  • photo allergy (delayed reaction to sun exposure)
  • skin response to bacteria, fungi, viruses
  • abnormal delayed response in atopic eczema
  • all require initial sensitisation with antigen (allergen) and once sensitised any area of skin contact will react
22
Q

Describe contact hand dermatitis

A
  • small blisters (vesicles) and erosion due to delayed hypersensitivity to rubber chemicals
23
Q

Name some factors that will increase the potential of topical steroids to cause side effects

A
  • duration of therapy
  • steroid potency used
  • extent of application
  • occlusion eg skin folds, gloves etc
  • thin skin; elderly, children, face, genitalia
  • inflamed skin
24
Q

Describe the systemic side effects of steroids

A
  • syppression of HPA axis, by increasing negative feedback
  • cushings (rare)
  • growth retardation (extremely rare)
25
Q

Describe reversible steroid effects

A
  • poor wound healing
  • unstable pustular psoriasis
  • modification of existing disease
  • pigmentary changes
  • tinea incognito
  • tachyphylaxis
  • steroid folliculitis
  • steroid rosacea
  • peri-oral dermatitis
  • contact allergy
26
Q

What is tinea incognito?

A

A fungal infection masked by inappropriate use of topical steroid

27
Q

What is steroid folliculitis?

A

Pustules in hair follicles

28
Q

Describe permanent effects of steroids

A
  • poor wound healing
  • hirsutism
  • glaucoma, cataract
  • atrophy (thinned epidermis) and multiple telangiectasia (dilated superficial blood vessels)
  • atrophy, bruising
  • striae (stretch marks)
29
Q

How can the potential risks of steroids be reduced?

A
  • do not use topical steroids where they wont work; diagnosis not made, infection, urticaria, rosacea, acne etc
  • use the least potent preparation that is effective
  • short term higher potency and reduce use
  • know the quantities required for appropriate use
30
Q

Describe the quantities of steroid for appropriate use

A
  • 1 fingertip unit = 500mg, enough for 1 application to both palms
  • 1 standard tube of cream or ointment usually 30g
31
Q

Why are children more at risk of increased steroid side effects?

A

Due to a larger surface area to volume ratio

32
Q

Topical steroids may cause suppression of the pituitary-adrenal axis, why is it important to know if a patient has developed this?

A
  • our bodies production of glucocorticoids varies and increases markedly during stressful events
  • this feedback system does not work if enough exogenous steroid (oral or topical) is taken as this increases negative feedback
  • the normal response to stress is then lost and additional exogenous steroid may need to be given to cover the episode

Dermatology (10 decks)

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