Immunology and UV Flashcards
Describe a type 1 hypersensitivity reaction
-Mediated by crosslinking of IgE molecules on mast cells by allergen
=Degranulation of mast cells, and the clinical lesion is urticaria
Peanut allergy and latex
Assessment of type 1 hypersensitivity
- Measuring serum specific IgE to particular antigens (what were once called RAST tests)
- Application of the stimulus with a needle to the skin. A positive response, elicits triple response: erythema, wealing and an axon reflex
Describe type 2 hypersensitivity
-IgG antibody mediated cytotoxicity.
=Examples include the autoimmune blistering disorders such as pemphigoid and pemphigus
=some of the systemic vasculitides involving ANCA (antineutrophilic cytoplasmic antigen).
Describe type 3 hypersensitivity reaction
-Immune complexes form and deposition of these complexes in the vessel may lead to a series of changes including complement activation, and activation of polymorphs and macrophages, and subsequent tissue damage to vessels and surrounding tissue.
=The most common clinical example would be leucocytoclastic vasculitis which can be a response to drugs, infections or a cutaneous manifestation of a systemic inflammatory disorder such as rheumatoid arthritis or SLE
Describe the type 4 hypersensitivity reaction
-T-cell mediated reaction, and clinically presents as eczema (dermatitis).
=Nickel allergy, or allergic contact dermatitis in response to a plaster.
-Immunological memory. A
-Delayed type
-Patch testing
UVB vs UVA
-Erythemal activity of sunshine (~80%) comes from the UVB component.
-So, although most radiation is UVA, UVB is so much more effective at inducing erythema, that most burning is due to the UVB component
Clinical epidemiology of diseases
-Skin cancer: 20% in lifetime
-Eczema: 15%
-Psoriasis: 2%
-Moderate to severe acne: 20%
Main causes of death from skin disease
-Skin cancers
-Blistering eruptions
-Cutaneous adverse effects of drugs
