Skin & Immune Mediated Diseases 3

Question 1

what are hypersensitivtity reactions

Answer 1

an exaggerated or inappropriate immune response to a mild pathogen or innocuous substance (allergen)

Question 2

what is an autoimmune disease

Answer 2

a specific humoral or cell-mediated immune response against the constituents of the body’s own tissues (auto-antigens)

Question 3

what are the types of hypersensitivity reactions

Answer 3

type I: anaphylactic, immediate

type II: antibody-dependent, cytotoxic

type III: immune complex mediated

type IV: cell-mediated, delayed

the host reponse to an imagined insult or an over-reaction to a real (but sometimes unidentified or unknown) infectious agent (ex. aberrations of normal immune reactions)

Question 4

what is type I hypersensitivity

Answer 4

production of antigen specific IgE –> IgE is bound to mast cell membranes

re-exposude to antigen

mast cell degranulation –> release of vasoactive mediators (histamines and prostaglandins) –> severe systemic reaction anaphylaxis or a milder local reaction

Question 5

what is anaphylaxis/anaphylactic shock

Answer 5

immediate systemic reaction caused by rapid IgE-mediated

Question 6

what does anaphylaxis/anaphylactic shock cause

Answer 6

immune release of potent mediators from tissue mast cells and peripheral basophils

serious allergic reaction that is rapid in onset and may cause death

Question 7

what does anaphylaxis/anaphylactic shock involve

Answer 7

involves skin +/- mucosal tissue; resp. system; gastrointestinal system; reduced BP

Question 8

what is the process of anaphylaxis/anaphylactic shock

Answer 8

release of vasoactive mediators > systemic vasodilation & increased vascular permeability > hypotension & tissue hypoperfusion

Question 9

what arre the triggers of anaphylaxis

Answer 9

foods

medication

venoms

unidentified

(not all reactions involve IgE –> some triggers directly stimulate mast cells)

Question 10

what are examples of type I hypersensitivity

Answer 10

1. apopic dermatitis
2. insect bite hypersensitivity (flea bite)
3. drug eruptions
4. food allergy

Question 11

what accounts for majority of skin disease in dogs and cats

Answer 11

atopic dermatitis

flea bite hypersensitivity

Question 12

what causes atopic dermatitis

Answer 12

multifactorial (genetics + environment)

Question 13

what is a common cause of atopic dermatitis

Answer 13

environmental allergens –> commonly house dust mites, insects, pollen, mold, dander of other animals

Question 14

what is the predisposition of atopic dermatitis

Answer 14

seems to be inherited

10% of dogs affected

esp WHWTs, cairns, scotties, boxers

Question 15

what does atopic dermatitis cause and where are common locations

Answer 15

pruritic dermatitis and otitis (conjuctivitis)

face, feet, ventrum

itching, red skin, loss of fur, small pus filled or solid bumps in skin, sores that might ooze, recurrent skin and ear infections

Question 16

what does atopic dermatitis appear histologically

Answer 16

acute inflammation with mast cell rich infiltrate

Question 17

®how do allergies cause atopic dermatitis

Answer 17

allergens can be absorbed via the skin +/- inhaled

Question 18

what contributes to the pathogenesis of canine atopic dermatitis

Answer 18

abnormal skin barrier

1. variation in filaggrin expression
2. disorganized lipid lamellae
3. altered balance of antimicrobial peptides

Question 19

what research is being done to prevent atopic dermatitis from abnormal skin barrier

Answer 19

repair lipid barrier in dogs by topical applications or nutritional supplements

Question 20

what is insect bite hypersensitivity

Answer 20

allergic dermatitis –> acute or more often chronic

Question 21

what triggers cause insect bite hypersensitivity

Answer 21

1. fleas
2. biting midges
3. black flies
4. mosquitoes

Question 22

how does insect bite appear on histology

Answer 22

focal necrosis beneath surface crust

reaction often characterized by eosinophils

Question 23

what is flea bite hypersensitivity

Answer 23

type 1 hypersensitivity (and/or type IV)

common - no breed predilection

may be seasonal –> summer & autumn

Question 24

what does flea bite hypersensitivity

Answer 24

pruritic papular dermatitis (miliary eczema)

dorsal lumbosacral area, neck, inner thighs, abdomen

Question 25

what is the features of flea bite hypersensitivity histology

Answer 25

may include eosinophils in dermal infiltrate and/or intraepidermal eosinophilic abscesses

Question 26

what is this

Answer 26

flea bite hypersensitivity eosinophil exocytosis, pustules & scale-crust

Question 27

what is this

Answer 27

crusted papules & alopecia

Question 28

what is type IV hypersensitivity delayed type hypersensitivity

Answer 28

DTH reactions involve same processes as cell-mediated immunity to microbial infection --\> not dependent on antibody balance swings from protection to tissue damage if the stimulus is great or unusually persistent

Question 29

what occurs in type IV hypersensitivity

Answer 29

sensitized T-cell population develops after initial contact with antigen via ACPs --\> re-exposure --\> lymphocyte activation --\> cytokine release --\> macrophage infiltration tissue damage is due to activated macrophages and cytotoxic T cells

Question 30

what are delayed hypersensitivity reactions

Answer 30

Question 31

what is the tuberculin test

Answer 31

an example of DHT 1. antigen introduced into subcutaneous tissue and processed by local antigen-presenting cells 2. A TH1 effector cell recognized antigen and release cytokines which act on vascular endothelium 3. recruitment of T cells, phagocytes, fluid and protein to site of antigen injection causes visible lesion

Question 32

how does DTH reaction cause a granuloma

Answer 32

granuloma formation depends on prolonged stimulation (\> 2 weeks)

Question 33

what is a disease that causes granulomas

Answer 33

tuberculosis

Question 34

what is allergic contact dermatitis

Answer 34

type IV hypersensitivity chemical (hapten) binds to epidermal proteins to form allergen not commonly diagnosed in animals --\> difficult to distinguish from irritant contact

Question 35

what is the appearance of allergic contact dermatitis

Answer 35

variably pruritic maculopapular dermatitis --\> sparsely haired regions affected especially ventrum --\> feet, legs, perineum, scrotum, chin and pinnae

Question 36

what is the histological appearance of allergic contact dermatitis

Answer 36

chronic dermatitis with hyperplasia, hypergranulosis, compact hyperkeratosis and lymphocyte exocytosis

Question 37

what is type III hypersensitivity

Answer 37

direct damage mediated by antibodies to exposed cell surface antigens --\> antigen usually endogenous binding of antibody (IgG or IgM) +/- complement --\> cytolysis or cytotoxicity

Question 38

what causes type II hypersensitivity

Answer 38

underlies various autoimmune disorders affecting various tissues --\> pemphigus, pemphigoid (epidermal cells), hemolytic anemia (red blood cells)

Question 39

what type of hypersensitivity is sweet itch

Answer 39

?

Question 40

what triggers sweet itch

Answer 40

culicoides spp. hypersensitivity

Question 41

what are the key features of flea bite hypersensitivity

Answer 41

type I hypersensitivity seasonal --\> summer and autumn pruritic papular dermatitis (miliary excema) dorsal lumbosacral area, neck, inner thighs, abdomen histoloy: eosinophils in dermal infiltrate and/or intraepidermal eosinophilic abscesses

Question 42

what type of hypersensitivity is delayed type

Answer 42

type IV hypersensitivity

Question 43

name 2 autoimmune conditions which have a hypersensitivity component

Answer 43

type II hypersensitivity pemphigus, pemphigoid (epidermal cells), hemolytic anemia (RBCs)

Question 44

what is shown here

Answer 44

allergic contact dermatitis

Question 45

give an example of delayed type hypersensitivity relevant to vet med

Answer 45

tuberculosis

Question 46

what is the difference between hypersensitivity reactions and autoimmune disease

Answer 46

hypersensitivity: exaggerated or inappropriate immune response to a mild pathogen or innocuous substance (allergen) autoimmune: a specific humoral or cell-mediated immune response against the constituents of the body's own tissues (auto-antigens)