1What is Hypersensitivity?
-An exaggerated response to a typically harmless antigen that results in tissue injury, disease, or even death
- 4 groups - classified based on the immunologic mechanism
2What are the 4 classes found in hypersensitivity?
• Class I (aka anaphylactic hypersensitivity)
• Class II (aka antibody-mediated cytotoxic hypersensitivity)
• Class III (aka immune complex-mediated hypersensitivity)
• Class IV (aka cell-mediated hypersensitivity)
3What mediates the 4 classes of hypersensitivity?
• I, II and III are antibody-mediated, and called immediate hypersensitivity reactions (happen within few minutes to a few hours after contact with Ag)
• IV is T cell-mediated and called delayed hypersensitivity reaction (takes 24-48h)
4What is Class I also called?
allergies
5What are some examples of Class I causes?
hay fever, hives, allergic asthma, systemic anaphylaxis
6What is the major antibody involved, which is greatly increased in these patients?
IgE
7What is atopy, which explains Class I at the genetics level?
the inherited tendency to develop classic allergic responses to naturally occurring inhaled or ingested allergens
8In the Class I, which are the main players and why?
- IgE
- basophils, mast cells, eosinophils,
- they have receptor for IgE
9Which is the major cell for Class I hypersensitivity?
mast cells
10Which Th cells are imbalanced during Class I rxn?
Th1 and Th2 balance is shifted so that Th2 response will predominate
11What happens once the Th cells are activated? Which cytokines are produced?
Il-4 and Il-13 - cytokines responsible for B cell differentiation and IgE production
12How long does the immunologic reaction for Class I take?
30-60 minutes