Hypersensitivity Flashcards
Which hypersensitivities can lead to tissue damage?
Hypersensitivity 2 and 4
Which hypersensitivities are mediated by antibodies?
Hypersensitivity 2 and 3
Which hypersensitivity is responsible for ALLERGIC reaction?
Hypersensitivity 1
Which hypersensitivity is involves T cell mediated DTH?
Hypersensitivity 4
What is the mechanism of hypersensitivity 1?
- Th2 cells with cytokine IL-4
- trigger class switch in B cells
- IgE circulating binds FceR1 on MAST Cells and leads to activation of mast cell
- cross linking signal increases mast cell degranulation
- mediators increase inflammation
What receptor is important for Hypersenstivity 1 ? Which Antibody is involved ?
FceR1 receptor , IgE
What is immediate phase of H-Sensitivity 1 ?
increase in edema , vasodilationm, sm muscle contraction
What is latent phase of H-Sensitivity 1 ?
2-24 hours later … increase in leukocytes to the area (neutrophils, eusinophils and macrophages
What are the clinical syndromes of H-Sensitivity 1 ?
- asthma- increased capillary permeability in lungs , SOB
2. anaphylaxis - bronchi sm muscle vasodilation , decrease in BP
What can we use to detect Type 1?
Allergen testing
What is Hypersensitivity 2?
IgM and IgG against surface (cell surface or extracellular matrix
What are the mechanisms of Hypersensitivity 2? (2 main)
- Complement-mediated (cytotoxic)
• Opsonization ( increase in C3a / C5a or recruitment and activation of inflammatory cells )
- ENHANCES Phagocytosis (via FcRy / CR1 receptors)
2.Non-cytotoxic
• Change in physiologic behavior of a cell
Examples of Non-cytoxic effects of hypersensitivity 2?
- GRAVES disease
2. Myasthenia gravis
Graves disease?
- type of sensitivity?
- mechanism?
- sxs
- Type 2
- Ab binds TSH receptor stimulating TSh release without hormone (non cytotoxic)
- hyperthyroidism
Myasthenia Gravis
- type of sensitivity?
- mechanism?
- sxs
- Type 2
- Ab inhibits Acetycholine binding Ach receptor (non -cytotoxic)
- muscle weakness
Good pasture syndrome..
- type of sensitivity?
- mechanism?
- Type 2
- Ab binds protein in kidney glomeruli and lungs (cytotoxic ;complement/ Fc receptors)
- nephritis and lung hemmorhage
Rheumatic Fever..
- type of sensitivity?
- mechanism?
- sxs
- Type 2
- Ab binds strep cell wall Ag (cytotoxic; phagocytosis)
- myocarditis
What is Type 3 hypersensitivity?
Complement-mediated recruitment and activation of inflammatory cells resulting in some combination of arthritis, vasculitis and/or nephritis.
How does quinidine work ?
binds C3b —> to RBC—> hemolytic anemia
How does alpha-methyldopa work?
binds directly to RBC self Ag—-> hemolysis . (phagocytosis)
Systemic Lupus and inflammation response ?
nephritis, vasculitis , arthritis
Poststreptoccoal Glomuleronephritis and inflammation response ?
nephritis
Serum Sickness and inflammation response ?
SYSTEMIC vasculitis/ nephritis due to immune complex build up in circulation
Arthrus Reaction and inflammation response ?
LOCAL vasculitis , immune complex build up in local area
What is (2) mechanisms of type 4 hypersensitivity ?
Cytokine-mediated tissue damage • T cell IFN-y activation of macrophage • IL-17 recruitment and activation of neutrophil Direct killing • CTL-mediated cellular death
Which T cells are involved in DTH ?
Th1 and Th17
What are two major triggers of Hypersensitivity 4?
- M tuberculosis
2. contact by poison ivy, metals, chemicals
What is the principle difference between type II and type III hypersensitivity?
a. whether Ab reacts with Ag on cell or reacts with Ag before it interacts with cell
b. the class isotoype of Ab
c. the participation of complement
d. the participation of T cells
A.
Type 2 deals with Ab binding to cell surface or ECM Ag
Type 3 involves Immune complex formation before interaction with cell
two important properties of allergens?
- binds with specificity to IgE
2. can bind IgE with LOW concentration (low threshhold)
