Allergy Flashcards
How does someone become allergic to an allergen
Allergen Develops
1. Allergen enters blood stream
2. B cells differentiate into plasma cells and make antibodies
3. Antibodies attach to mast cells
Allergic reaction
4. allergen binds to antibodies on amst cell
5. histamine is released from the mast cell
6. Allergic reaction happens
What are the 4 types of hypersensitivity reactions?
- IgE-mediated allergic reactions
- tissue specfic reactions
- immune complex - mediated reactions
- cell - mediated, delayed type reactions
What happens in a type 1 hypersensitivity reaction? (IgE-mediated allergic reactions)
IgE antibodies trigger mast cells and basophils to release histamine and other chemicals.
Classic allergy reaction
What happens in a type 2 hypersensitivity reaction? (tissue specific reaction)
The body produces IgG or IgM antibodies that bind to its own cells, marking them as “foreign.” This leads to destruction of these cells via the complement system or immune cells.
(antibodies attacking cells)
What happens in a type 3 hypersensitivity reaction? (immune complex)
Antigen-antibody complexes (IgG or IgM) form in the blood and get trapped in tissues, causing inflammation and tissue damage through complement activation and immune cell recruitment.
(immune complexes clogging up tissue)
What happens in a type 4 hypersensitivity reaction? (cell mediated - delayed)
T-cells, not antibodies, cause inflammation. After exposure to an antigen, sensitized T cells recruit macrophages and other immune cells to attack tissues.
(delayed reaction delivere by t-cells)
What is the mechanism of action of histamines
- Dilation of capillaries and venules - decreases cardiac preload, stoke volume, and cardiac output
- Contraction of nonvascular smooth muscle
- Increased capillary permeability - plasma leaks into interstitial space
What are the 2 other chemical mediators involved in allergic reactions?
Leukotrienes and Eosinophils
What is MOA of Leukotrines?
Potent bronchoconstrictor
Causeas
- Wheezing
- Coronary vasoconstriction
- Increased vascular permeability
What is the MOA of Eosinophils?
Perpetuates the inflammatory response
- degranulation of eosinophils release cytokines
- cytokines are singalling proteins that stimualte the immune response
What is the worry window for an allergic reaction with someone who has ingested an allergen vs someone who has an allergen injected
Injected (1 hour)
Injested (0.5-2.5 hours)
What are the 3 drugs used to treat allergic reactions?
Epi - Severe
Diphenhydramine - moderate to severe
Bronchoconstriction
