Hypersensitivity 1 Flashcards
What are hypersensitive reactions?
Hypersensitive reactions = excessive immune responses that cause damage
What are examples of antigens involved in hypersensitive reactions?
- Infection
- Harmless environmental substances
- Self-antigens
What are the 4 different types of hypersensitivity?
- Type I (Immediate)
- Type II (cell-bound antigen)
- Type III (immune complex)
- Type IV (Delayed)
Describe the process of influenze causing hypersensitivity?
- Virus damaged epithelial cells in respiratory tract
- Sometimes triggers exaggerated immune response
- High levels of cytokine secretion (cytokine storm)
- Cytokines attract leukocytes to the lungs, triggering vascular changes that lead to hypotension and coagulation
- In severe influenza, inflammatory cytokines spill into systemic circulation causing effects in remote parts of body, such as brain
Describe the process of dust causing hypersensitivity?
- Able to enter lower extremities of respiratory tract which are rich in adaptive immune response cells
- Can mimic parasites and stimulate antibody response
- If dominant antibody is IgE may trigger immediate hypersentivity, which manifests as allergy symptoms such as asthma or rhinitis
- If dominant antibody is IgG may trigger a different kind of hypersensitivity, such as farmer’s lung
Describe the process of nickel causing hypersensitivity?
Sometimes smaller molecule diffuse into the skin and can act as haptens (small molecule irritants that bind to proteins and elicit immune response), triggering delayed hypersensitive reaction – example is nickel causing contact dermaititis:
- Drugs administered orally, by injection or onto surface of body can elicit hypersensitivity reaction mediated by IgE or IgG antibodies or by T cells
- This is common, and even small doses can be life-threatening (idiosyncratic adverse drug reactions)
What is type I hypersensitivity?
Immediate hypersensitivity reaction to environmental antigens mediated by IgE
- Degranulation of mast cells and eosinophils
How quick is the onset of type I hypersensitivity?
- Within minutes of exposure
What is type 1 hypersensitivity basically?
An allergy
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What is another word for allergy?
Atopy
What are some presentations of type 1 hypersensitivity?
- Anaphylaxis
- Angioedema
- Urticaria
- Rhinitis
- Asthma
- Dermatitis
- Eczema
What is the atopic march?
Different presentations of type 1 hypersensitivty come and go at different ages
![](https://s3.amazonaws.com/brainscape-prod/system/cm/371/253/473/a_image_thumb.png?1609704198)
What are allergens?
Allergens = antigens that trigger allergic reactions
How can people be exposed to allergens?
- Inhalation, ingestion, contact or administered as drugs
What immunoglobulin mediates type 1 hypersensitivity?
IgE is required for type 1 hypersensitivity:
- B cells produce it when co-stimulated with IL-4 (secreted by TH2 cells)