Hypersensitivity Type 1 Flashcards
What is the main immunoglobulin (antibody) involved in hypersensitivity type 1, describe its function
IgE
Involved in allergies and parasite infections
Triggers inflammation because it exists pre-bound to basophils and mast cells and cause them to degranulate when they bind to their antigen
Exaggerated hypersensitivity type 1 responses are the common cause of
Allergies
Why do hypersensitivity type 1 reactions occur
Some animals produce more IgE (genetics)
Some antigens naturally produce very strong IgE responses (wasp and bee stings)
Why are hypersensitivity type 1 reactions considered immediate
Because IgE is pre-bound to mast cells which creates a rapid response to allergens (minutes)
Mast cells (sentinel) use IgE as a detection mechanism, Give an example of when the IgE response is appropriate?
Internal parasitic worms activate mast cells
Mast cells release chitinase which destroy the parasite’s outer covering and attracts eosinophils to destroy them
Describe the mechanism of activation of mast cells/basophils/eosinophils due to IgE what are the signs of this occurring?
IgE is pre-bound to these cells, When it’s appropriate antigen binds to IgE, it causes the mast cell to
Degranulate
Release interlukin 31 which sensitizes and stimulates pruritis
Release histamine and heparin (vasodilation and increased capillary permeability)
Attracts eosinophils
Signs: redness, pale MM, swelling (local edema) and itchiness
What is Atopy
The genetic predisposition to allergic disease (type 1)
Affected animals often have increased production of IgE and become sensitized to allergens common to the environment
What breeds are more susceptible to allergic diseases, which ones are less susceptible?
More: terriers, Dalmatians, retrievers
Less: non pure bred dogs
Describe the 3 main causes of allergic skin disease (atopic dermatitis), give an example of each.
Contact with environmental allergen (skin keratin defect -people with allergy to metal)
Injected allergen (flea saliva, culicoides/midge bites in horses called Sweet Itch, mosquitoes)
Ingested allergen(food) (from the gut, a small amount of dietary protein is absorbed intact, may or may not have GI signs, absorbed allergen may travel through the blood and bind to skin mast cells)
What are the signs of allergic skin disease (atopic dermatitis)
Often first seen in younger adults
Characterized by pruritis (intense itching in the feet and ears is often the first sign)
Skin lesions/changes (hives/urticaria)
Erythema (red skin)
Scratching/licking feet or rubbing leads to damage to the skin (alopecia, thickening (hyperkeratosis) and pigmentation)
Describe hives/urticaria
Raised lumps
Small or large
Warm, edematous
Pruritic
How is allergic skin disease (atopic dermatitis) diagnosed
Exclusion in the diet or environment: best for diet allergies (cut out possibilities one by one before diagnosing an allergy) -time consuming
Skin testing: inject potential allergens into the skin and see if there is a reaction (patches) -best for environmental allergies
Serum testing: better at ruling things out
How do you treat allergic skin disease (atopic dermatitis)
Washing/bathing frequently especially for contact dermatitis. Use tepid/cool water and moisturizing shampoos (oatmeal is a good anti-pruritic)
Reduce inflammation with antihistamines, corticosteroids, atopica (cyclosporin), oclacitinin (apoquel), monoclonal antibody (reduces itching)
How do you prevent allergic skin disease (atopic dermatitis)
Remove the source of allergen (environmental changes, reduce flea infestation, stable horses to avoid midges, diet changes)
Dietary exclusion (feed a simple diet, novel proteins, test different proteins)
Changing to a less inflammatory diet (increase omega-3 fatty acids -fish/flax/canola)
Desensitization (allergy shots, aim is to switch Ig synthesis to IgG, gradually increase doses)
Why is evening primrose oils not helpful in allergic skin disease
Contains omega 6 fatty acids (not omega 3s)
What is similar about hay Fever and asthma, what is the difference between the two?
Hay fever (allergic rhinitis) and asthma are both IgE mediated hypersensitivities of the respiratory tract. The difference depends on where the antigen is trapped
Large particles get trapped in the upper airways and cause
Hay fever
Small particles are carried down into the lungs and cause
Asthma
True or false
Hay fever is mainly a people problem
True
What are the signs of hay fever
Nose: sneezing, watery nasal discharge, blocked passages, itchy nose
Eyes: itchy, red, swollen, may feel gritty, blueness below skin (people)
Throat: soreness, itchy
Sleep: mouth breathing and fatigue
Who is asthma seen in
Cats
Basenij dogs
People
What are the signs of asthma
Wheezing
Dyspnea
Can be acute, severe and even fatal
How is asthma diagnosed
Administrating a bronchodilator -if it works then bronchoconstriction is causing the problem
Hay fever and asthma is less likely in humans if
You have lots of siblings and were raised on a farm
