Hypersensitivities Flashcards
Hypersensitivities
-exaggerated immunological reaction to a normally harmless antigenic stimulus resulting in injury to the host
-too much immunity
-type I, II, III, IV
Autoimmune disease
-develop when antibodies or leukocytes are reactive against self-antigens
Type I hypersensitivity
-immediate reaction
-animal comes into contact with antigen in which the animal already has mast cells
>histamine release= hyperemia, swelling, edema
Type II hypersensitivity
-like an autoimmune disease. Sensitivity to typically normal body structures. Lymphocyte mediated destruction
Type III hypersensitivity
-circulating antigen-antibody complexes accumulate and settle out on vessel wall
Type IV hypersensitivity
-delayed type hypersensitivity
-mediated by T cells and macrophages
Atopy (atopic dermatitis)
-type I
-allergen exposure usually through respiratory route
>excessive IgE with antigens trigger degranulation of mast cells
-major target is skin
Lesions of atopy
-Erythema (redness)
-Urticaria (itchy)
-self-inflicted trauma (licking, rubbing due to pruritus)
Food hypersensitivity dermatitis
-type I, III, IV reaction to food antigens
-non seasonal pruritic disease
Lesions of food hypersensitivity dermatitis
-erythema
-urtica
-self-inflicted trauma (licking, rubbing due to pruritus)
Pemphigus
-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)
Acquired myasthenia gravis
-autoimmune disease
-systemic muscular disease caused by type II reaction
>auto-antibodies against acetylcholine receptors which results in receptors not interacting with acetylcholine
Clinical signs of acquired myasthenia gravis
-muscle weakness
-fatigue exacerbated by exercise and resolves with rest
-megaesophagus +/- aspiration pneumonia
Iso (allo)-immune thrombocytopenia in piglets
-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
Idiopathic immune-mediated hemolytic anemia
-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)
Lesions of the idiopathic immune-mediated hemolytic anemia
-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)
Spherocytosis
-small erythrocyte lacking central pallor
-hallmark of immune mediated hemolytic anemia
Type III hypersensitivity reactions
-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
Equine Purpura hemorrhagica
-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
Purpura
-medium sized hemorrhages
Feline infectious peritonitis (FIP)
-progressive, often fatal immune-complex disease of cats caused by enteric coronavirus that progresses.
FIP viral spread systemically
-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
FIP infection
-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
Amyloidosis
-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)
Different types of amyloidosis
-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)
Renal amyloidosis
-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
