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
Asthma and hay fever is more likely if
There is a family history
What is an allergy often caused by if it is seasonal
Pollens from any type of plant or spores from fungi
What are allergies usually from if they are year round
Dust mites Roaches (produce allergen) Animal dander Fungi Molds
Dander allergens are more of a concern working
Indoors
True or false
Fine dander like on cats and rabbits are more likely to cause hay fever/asthma
True
What is the main allergen found on cats
Salivary protein that sticks to hair when licking
True or false
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
Anaphylactic shock is a major concern when;
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 veterinary practices always have on hand to prepare for anaphylactic reactions
Epinephrine
Antihistamines
Corticosteroids
Major signs of anaphylactic reactions are seen in the lungs and GI tract (shock organs) Whichever predominates depends on the species, describe when they are seen
Lungs AND GI: horses
Lungs only: cattle, sheep, cats
GI: dogs
Anaphylactic reactions also may be seen in the skin, especially in
Cats
Why are the kidneys and skeletal muscles not affected in anaphylaxis
Because mast cells are driving the anaphylactic response and these are mainly found at entry points of the body (GIT 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 the head
Weakness
Incoordination
Collapse
Death
Antihistamines are used in treatment of anaphylaxis in
Antihistamines: diphenhydramine (benadryl)
Often given in 2.2mg/kg
Often used in early signs
Why should you not give antihistamines in the 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 to 0.5 ml or 1:1000 epinephrine solution
IV fluids are given to help treat anaphylaxis to support circulation, what are some commonly used fluids
Corticosteroids
Prednisolon sodium succinate
Dexamethasone phosphate in water
A patient came in and got a first time vaccine along with a Booster vaccine, he ended up having a severe allergic reaction and came back to the clinic. What is the most likely cause of the reaction, explain 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 be primed against it before
