hypersensitivity Flashcards
What are the four types of hypersensitivity?
Type I: Anaphylactic and atopic.
Type II: Antibody-mediated.
Type III: Immune complex-mediated.
Type IV: Cell-mediated.
What mediates Types I, II, and III hypersensitivity?
Antibodies.
What is the mechanism of Type I hypersensitivity?
Immediate phase: Antigen cross-links preformed IgE on mast cells → degranulation → release of histamine, tryptase, and leukotrienes.
Late phase: Chemokines attract inflammatory cells (e.g., eosinophils) → inflammation and tissue damage.
How is Type I hypersensitivity diagnosed?
Skin test or blood test (ELISA) for allergen-specific IgE.
What are examples of Type I hypersensitivity?
Anaphylaxis (e.g., food, drug, bee sting).
Allergic asthma.
What is the mechanism of Type II hypersensitivity?
Antibodies bind to cell-surface antigens or extracellular matrix → cellular destruction, inflammation, and dysfunction.
What are the mechanisms of cellular destruction in Type II hypersensitivity?
Phagocytosis and/or complement activation.
NK cell-mediated antibody-dependent cellular cytotoxicity.
What diagnostic tests are used for Type II hypersensitivity?
Direct Coombs test: Detects antibodies directly attached to the RBC surface.
Indirect Coombs test: Detects unbound antibodies in serum.
What are examples of cellular destruction in Type II hypersensitivity?
Autoimmune hemolytic anemia.
Immune thrombocytopenia.
Transfusion reactions.
Hemolytic disease of the newborn.
What are examples of inflammation in Type II hypersensitivity?
Goodpasture syndrome.
Rheumatic fever. strep Ab against myoocytes
Hyperacute transplant rejection.
What are examples of cellular dysfunction in Type II hypersensitivity?
Myasthenia gravis. Ach receptors
Graves disease.
Pemphigus vulgaris.
what is thee treatment for type 1 hypersensitivity reactions ?
epinephrine
what. are the mediator’s of type 1 hyperseniitiity reactions ?
histamine
PGE2
PGD2
LTC4 LTD4
LTB4
EECCF-A
seretonin
platelet activating factor
neutral protease ( tryptasee)
heparin
how do you test for an IgE response ?
pin prick test , a positive result shows whela formation
what is the process when desensitizing an individual to a certain allergen ?
the aim is to switch the response from IgE to IgG
modified Th2 response
