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Dermatology > Skin Immunology and Biochemistry > Flashcards

Skin Immunology and Biochemistry Flashcards

1
Q

what 4 factors contribute to the skin’s effectiveness as a first line defence system?

A

structure - stratification, keratin layer
cell types - immune cells, keratinocytes
cytokines, chemokines, antimicrobial peptides
genetics

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2
Q

what are the 2 components of immune defence?

A

non-specific (innate)
- first line
specific (adaptive)
- self limiting

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3
Q

name 3 types of pathogenic immune responses

A

hypersensitivity
autoimmunity
immunodeficiency
autoinflammation

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4
Q

what is the difference between autoimmunity and autoinflammation

A 
autoimmunity = problem with adaptive immune system where it senses part of self as harmful and attacks
autoinflammation = problem with innate immune system where it reacts without cause or stimulation
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5
Q

how does the keratin layer form?

A

lipid rich barrier formed by differentiation of keratinocytes to corneocytes

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6
Q

what is present in the keratin layer?

A

filaggrin, involucrin, keratin,

Langerhans cells

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7
Q

what are keratinocytes and where are they mainly found?

A

structural and functional cells of the epidermis

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8
Q

what are 3 functions of keratinocytes?

A
  • sense pathogens via receptors on cell surface and mediate an immune response
  • produce antimicrobial peptides that directly kill pathogens
  • produce cytokines and chemokines
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9
Q

what are Langerhans cells?

A

type of dendritic cell found amongst keratinocytes in epidermis
main skin immune cell

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10
Q

what is the function of Langerhans cells and how are they characterised?

A

antigen presenting cells

characterised by birbeck granules

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11
Q

what type of T cells are found in the epidermis and the dermis?

A

epidermis = mainly CD8 T cells
Dermis = CD4 and CD8 T cells
other T cells like NK cells also found

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12
Q

CD4 T cells become helper T cells, which ones are associated with psoriasis and atopic dematits?

A

psoriasis = TH1
atopic dermatitis = TH2
Combination of both = TH17

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13
Q

where do T cells come from and where do they mature?

A

produced in the bone marrow

mature in the thymus

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14
Q

what is involved in antigen recognition and T cell activation?

A

interaction with T cell receptor and MHC which is enhanced by co-receptors CD4 and CD8

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15
Q

what is the role of CD4 cells?

A

helper T cells
TH1 = activate macrophages, IL2, IFN gamma
TH2 = help B cells make antibodies, IL4, IL5, IL6

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16
Q

what is the role of CD8 cells?

A

cytotoxic T cells
directly kill infected cells
protect against viruses and cancer

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17
Q

what is the role of interleukins?

A

communication between cells of the immune system

18
Q

what types of dendritic cells are found in the dermis and what do they do?

A

dermal DCs - Antigen presenting, secreting cyto/chemokines

plasmacytoid DCs - produce IFN alpha in diseased skin

19
Q

what cells are found in the dermis?

A 
macrophages
neutrophils
mast cells
dendritic cells
T cells
20
Q

what do mast cells do in the dermis?

A

effectors of IgE mediated immunity (allergy) by releasing inflammatory mediators upon binding of IgE/drugs etc (eg - histamine)

21
Q

which chromosome encodes for major histocompatibility complex?

A

6

22
Q

what does MHC class I do?

A

found on all cells and presents proteins (either self or foreign antigens) on surface of cell which are detected by cytotoxic T cells

23
Q

what does MHC class II do?

A

found only on antigen presenting cells

presents foreign antigens to T helper cells

24
Q

what benefits and problems can occur with MHC?

A 
benefits = anti-cancer mechanism
problem = transplant rejection
25
Q

name some skin conditions associated with inappropriate immune response

A 
psoriasis
atopic dermatitis
eczema
contact dermatitis
urticaria
SLE
bullous pemphigoid
skin infections/tumours
26
Q

what triggers the onset of psoriasis?

A

environmental trigger (trauma, stress, infection, drugs) in people who are genetically susceptible

27
Q

what are the hallmarks of psoriasis?

A

skin inflammation causing reversible plaques (red skin with overlying white scales)
joint pain

28
Q

is psoriasis associated with immune defence?

A

yes

psoriasis = non-ending, accelerated immune response (mainly phase 2) resulting in plaques loaded with natural antibiotic

29
Q

describe the pathogenesis of psoriasis?

A

keratinocytes under stress release interleukins, TNF and factors that stimulate dendritic cells to produce IFN alpha
these signals activate DCs which migrate to skin draining lymph node to present to T cells
T cells are attracted to the dermis by chemokines and secrete ILs which stimulate keratinocyte proliferation

30
Q

what other factors play a role in psoriasis pathogenesis?

A 
CD8 cells
dermal fibroblasts (release growth factors for keratinocytes and epidermis)
31
Q

what 2 symptoms must be present in a diagnosis of eczema?

A

dry skin and overactive immune response to microbes causing itching etc

32
Q

what causes eczema?

A

impairment of skin barrier
- mutation in filaggrin gene = cant bind water = dry skin
- reduced anti-microbial peptide in skin
allows access to allergen and promotes microbe colonisation

33
Q

what cells are involved in eczema?

A 
TH2
dendritic cells
keratinocytes
macrophages
mast cells
34
Q

give 3 autoimmune skin conditions

A

psoriasis
vitiligo
SLE

35
Q

what are the 2 types of immunodeficiency and give examples

A 
primary = inherited defect (genetic)
- DiGeorge syndrome
Secondary = acquired
- AIDS
- malignancy
- aging
36
Q

describe type 1 hypersensitivity

A

allergy (IgE mediated)
1st exposure produces IgE which binds to FcεR1 receptors on mast cells
2nd exposure = receptor crosslinking , signal transduction and mast cell degranulation

37
Q

what hypersensitivity is important in autoimmunity and transplantation?

A

type 2

38
Q

what mediates type 2 hypersensitivity?

A

antibodies

IgM and IgG

39
Q

what mediates type 4 hypersensitivity and what happens?

A

TH1 cells

T cell mediated response which then recruits other cells to site

40
Q

give examples of type 4 hypersensitivity

A

tuberculin reaction
contact allergy (nickel)
drugs

Dermatology (38 decks)

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