4.2 Allergy and autoimmunity Flashcards
allergy:
inappropriate immune response to harmless foreign antigen
allergy: 2 types of reactions
1) systemic allergic reaction
2) localized allergic reaction
localized allergic reaction
reaction at site of exposure
- skin
- respiratory tract
- GI tract
Type 1 allergic disease:
- Most common
- IgE mediated
- immediate-type hypersensitivity
Type Iv allergic disease:
- T cell mediated
- delayed -type
Type 1 hypersensitivity spectrum of severity:
- Urticaria: skin
Can progress to: - Angioedema: subcutaneous tissue/ swelling
Can progress to: - Anaphylaxis: Fatal
Therapy for systemic hypersensativity:
- Epinephrine (epi-pen)
- antihistamines (relieve fever, hives)
- steroids (dexamethasone, prednisolone)
*Often administered intravenously
Allergic skin disease:
Most common type 1 hypersensitivity:
- flea allergic dermatitis
- atopic dermatitis
- feline eosinophilic granuloma complex
- sweet itch in horses
- sometimes in Type IV ( allergic contact dermatitis
Flea-allergic dermatitis:
- Type 1 hypersensitivity in antigenic components in flea saliva
- dogs scratch
- cats overgroom - hair loss is common sign
Canine atopic dermatisis:
- allergic reaction to environment allergens
- dogs become very itchy and cause secondary trauma
- often opportunistic infection also present
Sweet itch in horses:
- allergic reaction to midge bites
- often affect the dorsum of the tail base
- intensely itchy
Allergy testing types:
- intradermal skin test
- serology blood test (allercept)
Problem with allergy test?
is making sure that the test is picking up igE because igE is the antibody associated with type 1 hypersensitivity
Allergic respiratory disease:
- cats
-dogs
- horses
cats: asthma
dogs: allergic bronchitis
horses: inflammatory airway disease
inflammatory airway disease in horses:
- allergic response to mmoldspores in crappy hay
- coughing, wheezing, exercise intolerance
Immune-mediated GIT disease:
- Gluten sensitive
- IBD
Gluten-sensitive enteropathy:
- Hypersensitivity to gluten in the diet
- chronic diarrhea and weight loss
- common in Irish setter
IBD:
inappropriate immune reactivity to protein in diet or antigen coming from microbial flora
Mucosal immunity: viruses and bacteria
- Gut is exposed to the virus and bacteria and antigen stimulates a response that generates secretory igA
- is transported across the mucosal epithelium and forms a neutralization barrier
mucosal immunity: parasite
- igE is stimulated and binds to tissue mast cells and protects from parasites trying to get through epithelium
mucosal tolerance: harmless antigen
- dietary protein or antigen from microflora
- expect to see tolerance and production of regulatory T cells that produce immunosuppressive cytokines that switch off immune repsonse
Underlying causes of IBD:
- increased intestinal permeability ( more antigen gets across)
- to much IgE produced against harmless antigen
- IGA Deficiency
- Poor T regulatory cell response
- defective innate immune response to bacteria
Ciclosporin =
immunosuppressive drug
For autoimmune disease to happen:
- a breakdown intolerancee to self antigen
- failure to regulate pathological immune response
Susceptibility to autoimmune disease:
- genetic factor (MHC genes play a critical role)
- Hormonal factors ( progesterone and estrogen)
- environmental factors ( stress, diet, vitamin D)
IgE is associated with
allergic disease, NOT autoimmune disease
Type II automimunity:
- Production of igM or igG to cell surface antigens or extracellular proteins
- autoimmune attack on target cell ( red blood cells, platlets)
- autoimmune attack on protein function: antibodies against acetocolyine receptors in myasthenia gravis
Type III autoimmunity:
- antibody (igG) binding in solution
- immune complex disease
- deposition of Ag/Ab complexes in blood vessels
- multisystemic immune-mediated disease
ex: glomerulonephritis ( fluorscence )
Type IV autoimmunity:
mediated by
- CD4 TH1 activating macrophages in the abscess of infection
- CD8 accidentally killing healthy cells that they think are virus but they arent
Type IV autoimmunity: Rheumatoid arthris
Rheumatoid arthritis:
packed full of:
- macrophage
- T cells
- pro-inflammatory cytokines
when activated produce Pro-inflammatory cells and secrete collagenase
Articlar cartilage is made of
type II collagen
What does collagenase do to collagen?
digest it
Type IV autoimmunity: Hypothyroidism
- lymphocytic thyroiditis
- likely T-cell mediated
- they think the thyroid gland is bad and then target and destroy thyroid
Type IV autoimmunity: Keratoconjunctivitis sicca:
- dry eye
- immune-mediated destruction of lacrimal gland
- probably T cell-mediated
- Treat with ciclosporin eye drops ( immunosuppressive)
Treatment of autoimmune disease:
- predinisolone: 1st tablet to use, use in high doses
- Ciclosporin (atopica): interferes with T cell signaling
- Azathioprine: treat rapidly dividing cells
- Cyclophosphamide: treat rapidly dividing cells
