Hypersensitivities

Question 1

Hypersensitivities

Answer 1

-exaggerated immunological reaction to a normally harmless antigenic stimulus resulting in injury to the host
-too much immunity
-type I, II, III, IV

Question 2

Autoimmune disease

Answer 2

-develop when antibodies or leukocytes are reactive against self-antigens

Question 3

Type I hypersensitivity

Answer 3

-immediate reaction
-animal comes into contact with antigen in which the animal already has mast cells
>histamine release= hyperemia, swelling, edema

Question 4

Type II hypersensitivity

Answer 4

-like an autoimmune disease. Sensitivity to typically normal body structures. Lymphocyte mediated destruction

Question 5

Type III hypersensitivity

Answer 5

-circulating antigen-antibody complexes accumulate and settle out on vessel wall

Question 6

Type IV hypersensitivity

Answer 6

-delayed type hypersensitivity
-mediated by T cells and macrophages

Question 7

Atopy (atopic dermatitis)

Answer 7

-type I
-allergen exposure usually through respiratory route
>excessive IgE with antigens trigger degranulation of mast cells
-major target is skin

Question 8

Lesions of atopy

Answer 8

-Erythema (redness)
-Urticaria (itchy)
-self-inflicted trauma (licking, rubbing due to pruritus)

Question 9

Food hypersensitivity dermatitis

Answer 9

-type I, III, IV reaction to food antigens
-non seasonal pruritic disease

Question 10

Lesions of food hypersensitivity dermatitis

Answer 10

-erythema
-urtica
-self-inflicted trauma (licking, rubbing due to pruritus)

Question 11

Pemphigus

Answer 11

-autoimmune disease (type II)
>immune response against the desmosomes preventing cells from sticking together
Results in blisters and eventually ulcers and erosions (usually at mucocutaneous junctions)

Question 12

Acquired myasthenia gravis

Answer 12

-autoimmune disease
-systemic muscular disease caused by type II reaction
>auto-antibodies against acetylcholine receptors which results in receptors not interacting with acetylcholine

Question 13

Clinical signs of acquired myasthenia gravis

Answer 13

-muscle weakness
-fatigue exacerbated by exercise and resolves with rest
-megaesophagus +/- aspiration pneumonia

Question 14

Iso (allo)-immune thrombocytopenia in piglets

Answer 14

-sows are sensitized to platelet antigens of piglets. They develop anti-platelet antibodies and secrete them into the colostrum. These colostral antibodies are ingested by the piglets where they bind to their platelets and destroy them.
>Results in thrombocytopenia and widespread hemorrhages

Question 15

Idiopathic immune-mediated hemolytic anemia

Answer 15

-most common in dogs
-auto-antibodies are developed against erythrocytic antigens
>resulting in RBCs being phagocytosed by macrophages in the spleen (extravascular hemolysis-serum will be normal) OR hemolysis by complement (intravascular hemolysis- serum will be red)

Question 16

Lesions of the idiopathic immune-mediated hemolytic anemia

Answer 16

-regenerative anemia (bone marrow hyperplasia=red bone marrow
-icterus (pre-hepatic) OR sometimes very pale mucous membranes
-enlarged spleen due to activation of macrophages and extramedullary hematopoiesis
-centrilobular hepatic necrosis (nutmeg liver) due to hypoxia (because anemia)

Question 17

Spherocytosis

Answer 17

-small erythrocyte lacking central pallor
-hallmark of immune mediated hemolytic anemia

Question 18

Type III hypersensitivity reactions

Answer 18

-difficult to identify
-usually follow an infection resulting in high production of antibodies and high levels of antibody-antigen complexes that float around by themselves. They tend to settle on blood vessel walls and the glomeruli

Question 19

Equine Purpura hemorrhagica

Answer 19

-occurs after a Streptococcus equi infection
-some horses have high levels of antigen-antibody complexes in circulation which deposit on the vessels with consequential vasculitis, generalized edema and purpura

Question 20

Purpura

Answer 20

-medium sized hemorrhages

Question 21

Feline infectious peritonitis (FIP)

Answer 21

-progressive, often fatal immune-complex disease of cats caused by enteric coronavirus that progresses.

Question 22

FIP viral spread systemically

Answer 22

-believed to be due to type III hypersensitivity reaction
-spread by infected macrophages
>immune complexes are deposited on the venular walls and cause type III immune reaction

Question 23

FIP infection

Answer 23

-depends on the cell mediated immunity of the animal
>strong and rapid Cell mediated immunity leads to virus being contained and eradicated
>weak cell mediated immunity leads to effusive wet form of FIP with marked fibrinous exudation
>moderately strong cell mediated immunity leads to dry form with granulomatous inflammation

Question 24

Amyloidosis

Answer 24

-a pathogenic proteinaceous substance
>waxy, pale appearance
-diagnosed by biopsy
-observed microscopically: beta pleated sheets (hard for body to remove), amorphous, eosinophilic, extracellular, congo red stain with polarized light (pink/red and birefringent green)

Question 25

Different types of amyloidosis

Answer 25

-AA: most common, accumulation of acute phase protein called Amyloid a

-AL: rarely seen in animals, largely a disease of humans. Light chains.

-IAPP: normal component co-secreted with insulin by beta-cells. Occurs in islet beta-cells, linked with diabetes in cats (secrete large amounts of insulin because they are insulin resistant, and increased IAPP occurs which can cause the death of islet cells)

Question 26

Renal amyloidosis

Answer 26

-leads to renal failure and uremia because the amyloid interferes with the blood supply to the nephrons and renal tubular atrophy occurs
-kidneys are enlarged and pale yellow-brown
-occurs in glomeruli, renal tubules, arterioles
>affects normal filtration and results in proteinuria