Hypersensitivity Type 3

Question 1

What is the general idea behind the type 3 hypersensitivity

Answer 1

Immune (antigen-antibody) complex disease

The response from the immune system to an antigen damages the host

Question 2

What does complement activation stimulate

Answer 2

Attracts neutrophils

Triggers inflammation

Question 3

Describe the mechanism behind how hypersensitivity type 3 reactions damage the host

Answer 3

Antibody binds to antigen (antigen typically from an infection)

Complexes filtered out or precipitate out into various locations

Antibody will then activate complement and attract neutrophils

Or

Antibody will bind to macrophages and mast cells which degranulate and release mediators that stimulate inflammation

This is a normal response, but in a hypersensitivity, large amounts of complexes cause excessive activation and disease

Question 4

Where are some sites damage usually occurs due to hypersensitivity Type 3 reactions

Answer 4

Lungs (local)

Kidneys and joints (systemic)

Question 5

What is hypersensitivity pneumonitis

Answer 5

Due to an inhaled allergen

This is often due to heat tolerant molds growing on damp hay (major problem since spores are small and get inhaled into the lungs)

Antigen-antibody complexes depositors in lungs (whole lung is affected, causing inflammation and fibrosis in chronic cases -scarring)

Question 6

What is the different between asthma and hypersensitivity pneumonitis (type 3 reaction)

Answer 6

Differences from asthma:

1) type of inflammatory cell
- eosinophils in asthma
- neutrophils in hypersensitivity pneumonitis

Both respond to bronchodilators

In both you see bronchoconstriction and Dyspnea (just caused by different things)

In hypersensitivity pneumonitis the early inflammatory response causes damage

Question 7

What are some common examples of type 3 hypersensitivity reactions

Answer 7

Heaves (COPD), Recurrent airway obstruction (RAO) of horses

Allergic pneumonitis of cattle (atypical interstitial pneumonia of cattle, hypersensitivity pneumonitis) and people (farmer’s lung)

Question 8

What are the clinical signs of the common hypersensitivity type 3 reactions? What is the treatment?

Answer 8

Signs: cough, increased respiratory rate, wheezing

Treatment: remove contact with allergen, corticosteroids, bronchodilators

Question 9

What are 2 diseases caused by precipitation of circulating complexes seen with type 3 hypersensitivity reactions

Answer 9

Blue eye in dogs

Glomerulonephritis

Question 10

What is blue eye in dogs

Answer 10

Corneal edema (blue) and uveitis (inflammation of the uvea -middle layer of the eye, ciliary body, choroid, iris)

following infectious canine hepatitis (adenovirus, CAV-1) (could be from the disease or older type vaccinations of the disease)

Immune complexes deposited in capillaries around the iris

Signs start in 2-3 weeks following the infection

Self cures with time

Question 11

What is glomerulonephritis

Answer 11

Immune complexes get filtered out at the glomeruli and become trapped in the glomerular capillaries and cause kidney damage

This needs a continuous source of antigen to cause chronic disease (chronic viral or bacterial diseases such as EIA in horses, pyometra in dogs, heart worms in dogs, Lyme disease or feline leukemia)

See heavy proteinuria without evidence of a UTI due to damage of the kidney

Treatmeant: treat the primary cause/infection and possible use of corticosteroids to reduce antibody production

Question 12

What do corticosteroids do

Answer 12

Used to reduce inflammation and suppress the immune system

Question 13

What is a commons Type 3 hypersensitivity skin disease, describe it including signs and treatment

Answer 13

Purpura hemorrhagica in horses

Seen 2-4 weeks after S. Equi infection (strangles/pneumonia)

Immune complexes deposited in blood vessels of the skin (begin to circulate and get trapped in come capillaries and cause inflammation in areas they are trapped)

Patchy, symmetrical skin inflammation (heat, swelling, pain, may ooze serum, skin may slough off, hemorrhages on mucosal surfaces)

Signs: may have GI signs, depression, fever, tachycardia, tachypnea)

Treat with corticosteroids

Question 14

What is immune mediated arthritis of animals

Answer 14

In people it is called Rheumatoid arthritis

Swollen joints

Causes milk or moderate lameness

Question 15

True or false

Type 3 hypersensitivities have a longer duration than type 1 and 2

Answer 15

True

They are often chronic

Question 16

What antibodies cause the disease in type 3 hypersensitivities

Answer 16

IgM or IgG (activate complement and neutrophils)

Question 17

True or false
An important mechanism of type 3 hypersensitivities is that it needs constant/chronic exposure to antigen to cause the problem

Answer 17

True

Question 18

How can a type 3 hypersensitivity reactions cause local vs systemic disease

Answer 18

Local: lungs

Systemic: spread through circulation (deposited in capillary bed in the eyes, kidneys, skin, joints, etc)