18 Hypersensitivity/Autoimmune Dz

Question 1

What is a Type 1 hypersensitivity?

Answer 1

Immediate hypersensitivity (severe example: anaphylaxis)

Question 2

What is the MOA of a Type 1 hypersensitivity reaction?

Answer 2

Antigen binds allergen-specific IgE on mast cell –> mast cell degranulates

Question 3

What is a cutaneous type 1 hypersensitivity reaction?

Answer 3

Urticaria

Question 4

What is a Type 2 hypersensitivity?

Answer 4

Antibody mediated/cytotoxic hypersensitivity

Question 5

What is the MOA of a Type 2 hypersensitivity reaction?

Answer 5

Loss of self-recotnition; IgG antibodies are directed against the antigens of normal cells

Question 6

What is a Type 3 hypersensitivity?

Answer 6

Immune complex mediated hypersensitivity

Question 7

What is the MOA of a Type 3 hypersensitivity reaction?

Answer 7

IgG and IgM antigen-antibody complexes deposit along the basal lamina and activate the complement cascade

Question 8

What is a Type IV hypersensitivity?

Answer 8

Cell mediated (delayed) hypersensitivity. (Ex: allergic contact dermatitis; atopic dermatitis)

Question 9

What is the MOA of a type IV hypersensitivity reaction?

Answer 9

Delayed reaction mediated by T cells

Question 10

What is miliary dermatitis?

Answer 10

An allergic hypersensitivity reaction in cats resulting in tiny crusted papules

Question 11

What predisposes horses to Culicoides hypersensitivity?

Answer 11

Genetic predilection

Question 12

Where on the body will Culicoides hypersensitivity lesions be found?

Answer 12

Dorsal presentation: Face and ears, poll, crest, withers, base of tail
Ventral presentation: entire ventral midline

Question 13

How does atopic dermatitis start?

Answer 13

Transepidermal exposure and absorption of allergens via a defective epidermal barrier

Question 14

What do naive Langerhans cells do when they find an antigen?

Answer 14

Process the antigen and travel to a draining lymph node to present it to a naive T helper cell (Th0)

Question 15

What do naive T helper cells (Th0) activate to when presented with an antigen from a Langerhans cell?

Answer 15

Th2 phenotype helper T cells

Question 16

What cytokines do Th2 cells produce and what do they do?

Answer 16

IL-4 and IL-13 to stimulate B cells to produce allergen-specific IgE

Question 17

What do activated Th2 and allergen-specific IgE do in the dermis?

Answer 17

Activate/progress the itching and inflammation cycle

Question 18

What do Langerhans cells do upon re-exposure to an allergen?

Answer 18

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

Question 19

What happens when mast cells re-encounter an allergen?

Answer 19

Allergen specific IgE on the surface of the mast cell will cross-link with the allergen, causing degranulation

Question 20

How are autoimmune skin diseases diagnosed?

Answer 20

Skin biopsy

Question 21

What part of the skin is attacked in Pemphigus diseases?

Answer 21

Desmosomal proteins

Question 22

What does the clinical presentation of Pemphigus foliaceus look like?

Answer 22

Pustules and crusting lesions with a facial to generalized distribution, variable foot pad lesions (cats often have claw bed lesions), malaise. No mucosal involvement.

Question 23

What does a clinical presentation of Pemphigus vulgaris look like?

Answer 23

Coalescing erosions, ulcerations, and pustules; lots of mucosal involvement. Systemic illness.