Immunology Flashcards
What factors of the skin contribute to it as an immunological system?
Structure
Eg. keratin layer (stratum corneum), stratification
Immune system cells and keratinocytes
Cytokines, chemokines, eicosanoids, antimicrobial peptides
How can the innate immune system be described?
No memory
Non-specific
First line
How can the adaptive immune system be described?
Memory
Highly specific (Eg. antibodies)
Tolerance
Self-limiting
What is an antigen?
protein/peptide or polysaccharide that elicits an immune response
What are the jobs of keratinocytes in terms of the immune response?
Sense pathogens on cell surface receptors and mediate an immune response.
Produce antimicrobial peptides (AMPs) that can directly kill pathogens.
Produce cytokines and chemokines.
What type of immune cell are Langerhans cells?
Antigen presenting dendritic cell
What type of T cell is found in the epidermis?
CD8+ T cells
What type of T cell is found in the dermis?
CD4 + and CD8+ T
What subtype of CD4+ T cells give rise to the inflammation in Psoriasis?
TH1 (psoriasis)
What subtype of CD4+ T cells give rise to the inflammation in atopic dermatitis?
TH2 (atopic dermatitis)
What subtype of CD4+ T cells give rise to both psoriasis and atopic dermatitis?
TH17 (psoriasis and atopic dermatitis).
Describe the difference between CD8+T cells and CD4+T cells
CD4 = helper T cells CD8 = cytotoxic T cells
What types of dendritic cells are found in the dermis?
Dermal DC: involved in Ag presenting and secreting cyto/chemokines
Plasmacytoid DC (pDC): produce IFNα. Found in diseased skin
Name the preformed mediators often released from mast cells upon activation
Tryptase
chymase
TNF
histamine
What type of inflammatory mediators do mast cells have?
Preformed Newly synthesised (lots of these!)
What antibody triggers a mast cell response?
IgE
What does MHC stand for?
Major Histocompatibility Complex
Where is the DNA which codes MHC found?
Chromosome 6
What is the difference between Class I and II MHC?
Class I:
Found on almost all cells
Present Ag to cytotoxic T cells
Present endogenous Ag
Class II:
Found on APC (B cells, macrophages)
Present to TH cells
Present exogenous Ag
What are interleukins now being used for?
Targets of drug treatments
Why will a skin biopsy of a psoriasis patch grow no bacteria when incubated?
The red patches are loaded with antibiotics (peptides we make ourselves)
Why do people on antibiotics often experience fungal infection?
The antibiotics wipe out our own biofilm, therefore leaving a breading ground for other microbes to grow - eg. the fungus that causes thrush
Where does psoriasis usually occur on the body?
in areas of low grade trauma i.e. scalp - due to hair growing extensor surfaces of elbows lower back and buttocks - due to body weight resting on these
Describe the immunopathogenesis of psoriasis
KC under stress
Chemical signals activate DC
these drain to lymph node to activate T cells
T cells are attracted to the dermis by chemokines and secrete IL-17A/17F/22
CD8+ cells also contribute to pathogenesis.
Dermal fibroblasts become involved, which release KC and epidermal growth factors.
In what age group is atopic eczema most common?
Children
What is the immunopathogenesis of atopic eczema?
Mutations in fillagrin gene associated with severe/early onset disease.
Fillagrin helps retain moisture => without it skin = DRY
↓AMP in skin
Immune response is then mounted to microbes from the biofilm
What type of T cell links eczema to asthma and other allergic conditions?
TH2 cells
Give 3 examples of autoimmune skin conditions
Psoriasis
Vitiligo
Systemic lupus erythematosus
Give examples of things which could cause a Type 1 Hypersensitivity Reaction
Pollen (birch, oilseed rape)
Drugs (penicillin)
Food (nuts, eggs, seafood)
Insects/animals (bee sting, cat hair)
What antibodies mediate type II and III hypersensitivity reactions?
IgG and IgM
What can inflict a Type II or III hypersensitivity reaction?
Haemolytic disease of the newborn
Blood transfusion recipients
What cell mediates a Type IV hypersensitivity reaction?
Tuberculin reaction
Contact allergy
Metals (nickel, chromate), drugs.
When does a type IV hypersensitivity reaction peak?
Peaks at 24-48h after contact with Ag
What factors affect the skins immune response?
Organ transplant (Immunosuppression)
Sunlight/UV (Immunosuppression / Structure)
Ageing
