Hypersensitivity Reactions Flashcards
We can remember the Hypersensitivity Reactions by the mneumonic ABCD what does it stand for?
A - Atopic/allergy
B - AntiBody
C - Complex
D - Delayed
What are the two phases of Type 1 Hypersensitivity Reactions?
Immediate and Late
What are the example Tests that would be a Type 1 Hypersensitivity?
Skin tests and blood tests for allergen specific IgE
What occurs in the immediate phase of a Type 1 Hypersensitivity Reaction?
Antigen crosslinks IgE on presensitized mast cell
immediate degranulation
release of histamine and tryptase
What occurs in the late phase of Type 1 Hypersensitivity?
Chemokines ( eosinophils, inflammatory cells)
leukotrienes from mast cells
Inflammation and tissue damage
What is a test that is essentially a type 2 hypersensitivity?
Direct Coombs test - detects antibodies attached directly to the RBC surface.
What is a Type 2 Hypersensitivity?
Antibodies bind to cell surface antigens - > cellular destruction, inflammation, and cellular dysfunction.
What are two ways cells are destroyed in a type 2 hypersensitivity reaction?
What are example diseases?
Antibody coated cells
- Phagocytosed or Complement activation
- NK cell killing
AIHA, ITP, Transfusion reaction, Hemolytic dz of the newborn.
What are some example of inflammation (binding of cell surface) type 2 hypersensitivity reactions?
Goodpasture, RF, Hyperacute transplant rejection
What are example of cellular dysfunction (antibody bound to receptor) Type 2 hypersensitivity
MG, Graves, Pemphigus vulgaris
What is a Type 3 hypersensitivity?
Immune complex - Ag-Ab complexes activate complement, which attracts neutrophils, neutrophils release lysosomal enzymes.
What are the three things stuck together in Type 3 Hypersensitivity reactions?
Complement, Antibody, Antigen
What are the two big ones we need to know for Type 3 Hypersensitivities?
Arthurs Reaction - local subacute immune complex mediated of skin - > edema, necrosis, and complement activation
Serum Sickness - prototypic immune complex disease. Antibodies to foreign proteins are produced and 1-2 weeks later, antibody antigen complexes form and deposit in tissue -> complement activation leading to inflammation and tissue damage
What are type 4 hypersensitivity reactions?
T cell mediated (delayed)
- Direct cell cytotoxicity: CD8+ direct cell killing
- inflammatory reaction: CD4+ T cells recognize antigen and release inflammation inducing cytokines
No antibodies
