3.1.3 Cutaneous Allergic Reaction Flashcards Preview

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Flashcards in 3.1.3 Cutaneous Allergic Reaction Deck (9)
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Tuberculin PPD skin test is an example of what type of hypersensitivity?

Type IV


CD4 T cells are activated when they recognize antigens presented by?

MHC class II


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 constitute 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


How long do you leave the patches on during a patch test?



Linear rash can be associated with?

A contact dermatitis due to the brushing motion against the allergen


What is the basic overview 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 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 reg inflammation via T reg cells or the production of inflammatory mediators-PGs, LTs, and proteases. This lead to complement anaphylatoxins and then mast cell mediators

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