Allergic Reaction in the Skin Flashcards
Tuberculin PPD skin test is an example of which type of hypersensitivity?
Type IV
Pathology report referred to a sample as having a mononuclear cellular infiltrate and a diagnosis of allergic contact dermatitis was later established. What is the likely cells that were in the infiltrate?
T cells and macrophages constitue most of a mononuclear infiltrate in DTH lesions.
What test would be performed to assess the possibility of allergic contact dermatitis?
Patch test - applying patches impregnates with various allergens to the patient
What type of hypersensitivity are SLE and RA?
Type III
How long do you leave patches on during a patch test?
72 hours, got to get a cell immediated response
Linear Rash is assoicate with what?
Contact dermititis due to the brushing motion against an allergen line a leaf, the linear is the edge of the leaf contact point
What is the most common metal allergy?
NIckel Sulfate
What is the basic pathway of allergic contact dermatitis
Metal or other hapten exposure leads to sensitization. The antigen is presented on MHC class I and II. CD4 and CD8 expansion. Upon re-exposure to hapten there is T cell recruitment and macrophage recruitment and activation. This leads to inflammatory mediator production.
What does pruritic mean?
Itchy
What is the basic process of sensitization?
First exposure leads to binding to skin proteins and formation of neoantigen. The Ag is then presented on MHC II and creation of CD4 and CD8 memory cells.
After sensitization and upon second exposure what happens?
Memory T cells and activated macrophages lead to the production of chemokines and IFN-gamma This can have two outcomes. CD4 T cells down regulate inflammation via Treg cells or the produciton of inflammtory mediators like Prostaglandins, Leukotrines, and proteases. This lead to complement anaphylatoxins and then mast cell mediators.
