Hypersensitivity 1 Flashcards
What is the main immunoglobulin (antibody) involved in type 1? Function?
IgE
- involved in allergies and parasite infections
Triggers inflammation bc it exists pre-bound to basophils and mast cells
- 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
- dogs
some antigens produce very strong IgE responses
- wasp and bee stings (naturally programmed to create response, excessive IgE makes more severe)
Why are hypersensitivity type 1 reactions considered immediate?
IgE is pre-bound to mast cells
- created a rapid response to allergens (minutes)
Mast cells (sentinel) use IgE as a detection mechanism Example of when IgE response is appropriate
Internal parasitic worms activate mast cells
Mast cells release chitinase
- destroy 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 pre-bound to these cells
- when appropriate allergen binds to IgE, causes mast cell to degranulate
Release interleukin 31
- sensitizes and stimulates pruritis
Release histamine and heparin
- vasodilation and increased capillary impermeability
Attracts eosinophils
Signs: redness, pale MM, swelling (local edema), itchiness
Atopy definition
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: none 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 a metal allergy
Injected allergen
- flea saliva, culicoides/midge bites in horses - sweet itch, mosquitoes
Ingested allergen (food)
- small amount of dietary protein from gut 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
Pruritis (intense itching in the feet and ears often first sign)
Skin lesions/changes (hives/urticaria)
Erythema (red skin)
Scratching/licking feet or rubbing
- damages skin (alopecia, thickening - hyperkeratosis, 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: allergies
- cut out possibilities one at a time before diagnosing allergy
- time consuming
Skin testing: environmental allergies
- inject potential allergens into the skin an see if there is a reaction (patches)
Serum testing: better at ruling things out
How is allergic skin disease (atopic dermatitis) treated?
Washing/bathing frequently
- contact dermatitis*
- tepid/cool water and moisturizing shampoos (oatmeal = anti-pruritic)
Reduce inflammation
- antihistamines, corticosteroids, atopica (cyclosporin), oclacitinin (apoquel), monoclonal antibody (reduces itching)
How is allergic skin disease (atopic dermatitis) prevented?
Remove source or allergen
(environmental changes, reduce flea infestation, stables horses to avoid midges, diet changes)
Dietary exclusions (feed a simple diet, novel proteins, test different proteins)
Changing to less inflammatory diet (increase omega-3 fatter acids - fish/flax/canola)
Desensitization (allergy shots, aim is to switch Ig synthesis to IgG, gradually increase doses)
Is evening primrose oil helpful in allergic skin disease?
No
contains omega-6 fatty acids (not omega-3)
What is similar about hay fever and asthma?
What is the difference?
both IgE mediated hypersensitivities of the resp tract
Difference depends on where the antigen is trapped
Medical term for hay fever
Allergic rhinitis
Large particles get trapped in the upper airways cause?
Hay fever
Small particles carried down into the lungs cause?
Asthma
T or F
Hay fever is mainly a people problem
True
Signs of hay fever
Nose: sneezing, watery nasal discharge, blocked passages, itchy nose
Eyes: itchy, red, swollen, feel gritty, blueness bellow skin (only people)
Throat: soreness, itchy
Sleep: mouth breathing and fatigue
Who is asthma seen in
Cats
Basenji dogs
People
Asthma signs
Wheezing
Dyspnea
Can be acute or 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
Lots of siblings and we raised on a farm
Asthma and hay fever more likely if
There is a family history
What are seasonal allergies often caused by?
Pollen from any type of plant or spores from fungi
What are year round allergies usually caused by?
Dust mites Roaches (produce allergen) Animal dander Fungi Molds
Dander allergens are more of a concern when
Working indoors
T or F Fine dander (cats and rabbits) are more likely to cause hay fever/asthma
True
Main allergen found on cats
Salivary protein that sticks to hair when licking
T or F
There is a diet that contains antibodies against common cat salivary allergens to help reduce reactions in people
True
What is anaphylactic shock?
An extreme, life threatening allergic reaction to an allergen
When is anaphylactic shock a major concern?
Giving a biological product (vaccine) due to injection of an actual antigen or live virus
Penicillin (common)
How long does it take for an anaphylactic shock reaction to occur?
15-30 minutes
What should vet practices always have on hand in case of anaphylactic shock?
Epinephrine
Antihistamines
Corticosteroids
Describe when major anaphylactic shock signs are seen and in what species
Lungs AND GI: horses
Lungs only: cattle, sheep, cats
GI only: dogs
What species may anaphylactic reactions be seen in the skin?
Cats
Why are the kidneys and skeletal muscles not affected in anaphylaxis?
Mast cells are driving the anaphylactic response and are only found at entry points of the body (GI and lungs)
These areas have few sentinel cells
What are some common respiratory signs of anaphylaxis?
Increased RR
Dyspnea
Coughing
What are some common GI signs of anaphylaxis
Vomiting (not in horses)
Increased defecation/diarrhea (may be bloody)
What are some other signs of anaphylaxis?
Skin irritation (cats) and scratching around head
Weakness
Incoordination
Collapse
Death
Antihistamines are used in treatment of anaphylaxis in?
Antihistamines: diphenhydramine (Benadryl)
Give 2.2mg/kg
Often used in early signs
Why should antihistamines not be given in food/orally?
Takes longer to absorb
Patient may be vomiting or have diarrhea
What does epinephrine do in the treatment of anaphylaxis?
Stabilizes mast cells and stops degranulation
Reverses vasodilation
Dilates smooth muscle to help breathing
Rapidly absorbed if given IM or SQ
Dose for cats and dogs is 0.1 - 0.5 ml or 1:1000 epinephrine solution
What are some commonly used IV fluids to support circulation and help treat anaphylaxis?
Corticosteroids
Prednisolone sodium succinate
Dexamethasone phosphate in water
A patient came in and got a first time vaccine along with a booster vaccine
Ended up having a severe allergic reaction and came back to clinic
What is the most likely cause of the reaction? Why?
The booster vaccine (not the first time vaccine) because the immune system/body has been primed against the vaccine that was boosted at the first vaccination appointment so the reaction was ready the second time
The first time vaccine would not have created a reaction so fast because the immune system has not been previously primed against it
