Hypersensitivity and Autoimmune disease Flashcards
What are the types of hypersensitivity reactions?
Immediate (Type I)
Antibody-mediated (Type II)
Immune complex-mediated (Type III)
Delayed-type hypersensitivity (Type IV)
What are the immune mechanisms involved in a type I reaction?
Activation of Th2 cells resulting in the production of IgE which in turn binds to FceR on mast cells, basophils and eosinophils
What are the mechanisms of tissue injury behind a type I reaction?
Immediate reaction:
Degranulation and release of vasoactive amines (ie. histamine) and proteases
Late-phase reaction:
- Synthesis and secretion of prostaglandins and leukotrienes
- Cytokine-induced inflammation and leukocyte recruitment
What are the immune mechanisms involved in a type II reactions?
IgM and IgG against surface (cell surface or extracellular matrix)
Antibodies on top of tissue
What are mechanisms of tissue injury behind a type II reaction?
Complement mediated (cytotoxic):
- Opsonization and enhances phagocytosis
- Recruitment and activation of inflammatory cells
Non-cytotoxic:
Change in physiologic behavior of a cell
What are the immune mechanisms involved in a type III reaction?
Deposition of immune complexes comprised of IgM or IgG and soluble antigen
Complex inside tissue
What are the mechanisms of tissue injury behind a type III reaction?
Complement mediated recruitment and activation of inflammatory cells resulting in some combination of arthritis, vasculitis, and/or nephritis
What are the immune mechanisms involved in a type IV reaction?
Inflammatory cytokines, IFN-gamma and IL-17, produced by CD4+ Th1 and Th17 cells, respectively
What are the mechanisms of tissue injury behind a type IV reaction?
Only reaction due to T cells
Cytokine-mediated tissue damage:
- IFN-gamma activation of macrophage
- IL-17 recruitment and activation
Direct killing:
CTL-mediated cellular death
CD8+ CTLs (T-cell-mediated cytolysis):
Direct target killing, cytokine-mediated inflammation
What are some examples of Type I hypersensitivity?
Allergic rhinitis Systemic anaphylaxis Food allergies Wheal and flare Asthma
What are the allergens that cause allergic rhinitis?
Trees, grasses, dust, cats, dogs, mites
What are the clinical findings of allergic rhinitis?
Edema, irritation, mucus in nasal mucosa
What are the allergens that cause systemic anaphylaxis?
Insect stings, drug reactions
What are the clinical findings of systemic anaphylaxis?
Bronchial and tracheal constriction, complete vasodilation and death
What are the allergens that cause food allergies
Milk, eggs, fish, cereals, grains
What are the clinical findings of food allergies?
Hives and gastrointestinal problems
What is the wheal and flare?
In vivo skin testing for allergies
What are the clinical findings of the wheal and flare
Local skin edema, reddening, vasodilation of vessels
What are the allergens that cause asthma?
Inhaled materials
What are the clinical findings of asthma?
Bronchial and tracheal constriction, edema, mucus production, massive inflammation
What are examples of Type II hypersensitivity?
Autoimmune hemolytic anemia (HDNB) Acute rheumatic fever Goodpasture syndrome Transfusion reaction Autoimmune thrombocytopenia purpura Myasthenia gravis Graves disease Type II (insulin resistant) diabetes Pernicious anemia
What are the examples of Type III hypersensitivity?
Systemic lupus erythematosus Poststreptococcal glomerulonephritis Arthus reaction Serum sickness Polyarteritis nodosa Diffuse systemic sclerosis Limited scleroderma Sjorgren syndrome
What is the antigen involved in systemic lupus erythematosus?
dsDNA
Sm
Other nuceloproteins
What are the clinical manifestations of systemic lupus erythematosus?
Nephritis
Arthritis
Vasculitis
Butterfly facial rash
