18 Hypersensitivity/Autoimmune Dz Flashcards
(23 cards)
What is a Type 1 hypersensitivity?
Immediate hypersensitivity (severe example: anaphylaxis)
What is the MOA of a Type 1 hypersensitivity reaction?
Antigen binds allergen-specific IgE on mast cell –> mast cell degranulates
What is a cutaneous type 1 hypersensitivity reaction?
Urticaria
What is a Type 2 hypersensitivity?
Antibody mediated/cytotoxic hypersensitivity
What is the MOA of a Type 2 hypersensitivity reaction?
Loss of self-recotnition; IgG antibodies are directed against the antigens of normal cells
What is a Type 3 hypersensitivity?
Immune complex mediated hypersensitivity
What is the MOA of a Type 3 hypersensitivity reaction?
IgG and IgM antigen-antibody complexes deposit along the basal lamina and activate the complement cascade
What is a Type IV hypersensitivity?
Cell mediated (delayed) hypersensitivity. (Ex: allergic contact dermatitis; atopic dermatitis)
What is the MOA of a type IV hypersensitivity reaction?
Delayed reaction mediated by T cells
What is miliary dermatitis?
An allergic hypersensitivity reaction in cats resulting in tiny crusted papules
What predisposes horses to Culicoides hypersensitivity?
Genetic predilection
Where on the body will Culicoides hypersensitivity lesions be found?
Dorsal presentation: Face and ears, poll, crest, withers, base of tail
Ventral presentation: entire ventral midline
How does atopic dermatitis start?
Transepidermal exposure and absorption of allergens via a defective epidermal barrier
What do naive Langerhans cells do when they find an antigen?
Process the antigen and travel to a draining lymph node to present it to a naive T helper cell (Th0)
What do naive T helper cells (Th0) activate to when presented with an antigen from a Langerhans cell?
Th2 phenotype helper T cells
What cytokines do Th2 cells produce and what do they do?
IL-4 and IL-13 to stimulate B cells to produce allergen-specific IgE
What do activated Th2 and allergen-specific IgE do in the dermis?
Activate/progress the itching and inflammation cycle
What do Langerhans cells do upon re-exposure to an allergen?
Bind the antigen with cell membrane bound allergen-specific IgE on the surface of the Langerhans cell, then migrate and present the antigen to Th2 cells in the dermis
What happens when mast cells re-encounter an allergen?
Allergen specific IgE on the surface of the mast cell will cross-link with the allergen, causing degranulation
How are autoimmune skin diseases diagnosed?
Skin biopsy
What part of the skin is attacked in Pemphigus diseases?
Desmosomal proteins
What does the clinical presentation of Pemphigus foliaceus look like?
Pustules and crusting lesions with a facial to generalized distribution, variable foot pad lesions (cats often have claw bed lesions), malaise. No mucosal involvement.
What does a clinical presentation of Pemphigus vulgaris look like?
Coalescing erosions, ulcerations, and pustules; lots of mucosal involvement. Systemic illness.
