Hypersensitivity Flashcards
What are Hypersensitivity Reactions and to what stimuli?
Excessive immune responses that cause damage.
Response to different types of antigens:
- Infectious agents.
- Environmental substances
- Self antigens.
What is the relationship between Hypersensitivity and Infections?
Not all infections are capable of causing hypersensitivity reactions.
Infections that elicit hypersensitivity do not do so in every case.
In severe influenza, inflammatory cytokines also spill out into the systemic circulation, causing ill effects in remote parts of the body, such as the brain
*Cytokine storms - Similar with covid. Issues in lungs and coagulation
How does influenza cause Hypersensitivity ?
Influenza viruses can cause hypersensitivity:
- Influenza virus damages epithelial cells in the respiratory tract.
- Can sometimes elicit an exaggerated immune response.
- Can trigger high levels of cytokine secretion (cytokine storm).
- The cytokines attract leukocytes to the lungs and trigger vascular changes that lead to hypotension and coagulation.
In severe influenza, inflammatory cytokines also spill out into the systemic circulation, causing ill effects in remote parts of the body, such as the brain
How does Dust act as an environmental substance in Hypersensitivity?
Dust triggers responses because it is able to enter the lower extremities of the respiratory tract, an area rich in adaptive immune response cells.
Dust can mimic parasites and may stimulate an antibody response.
If the dominant antibody is IgE, it may subsequently trigger immediate hypersensitivity, which manifests as allergy symptoms such as asthma or rhinitis.
If the dust stimulates IgG antibodies, it may trigger a different kind of hypersensitivity, such as farmer’s lung.
What are Haptens?
Smaller molecules sometimes diffuse into the skin and may act as haptens, triggering a delayed hypersensitivity reaction.
Haptens are small molecule irritants that bind to proteins and elicit an immune response.
How what skin reactions can be caused by Hypersensitivity?
Contact dermatitis caused by nickel.
Drugs administered orally, by injection, or onto the surface of the body can elicit hypersensitivity reactions mediated by IgE or IgG antibodies or by T cells.
Immunologically mediated hypersensitivity reactions to drugs are quite common, and even small doses can trigger life-threatening reactions (idiosyncratic adverse drug reactions).
What are the different types of Hypersensitivty?
See Graph
What are the features of Type I hypersensitivity ?
Mediated through the degranulation of mast cells and eosinophils.
The effects are felt within minutes of exposure.
Immediate hypersensitivity, allergy
What are the features and causes of Atopy/Allergies?
Immediate hypersensitivity reaction to environmental antigens mediated by IgE.
Develops within minutes of exposure
Family history with atopy traits.
Atopy = allergy
- Anaphylaxis
- Angioedema
- Urticaria
- Rhinitis
- Asthma
- Dermatitis, eczema
Allergic march
*Patients who displays allergies at young age and develop later in life. Eczema and food allergies actually get better over time. Rhinitis gets worse overtime (more likely to develop if have eczema as have genetic predisposition)
What is this?
Angioedema
What is this?
Atopic Eczema
What is this?
Acute urticaria
How do allergens work and what is the most common one?
Antigens that trigger allergic reactions are called allergens.
They gain access to the body through inhalation, ingestion, contact or administered as drugs
Peanut allergy is the most common cause of severe allergic reactions.
Allergy to latex
Penicillin allergy, the allergen is β-lactam
What diffeent types of peanut allergies is there?
Peanut allergy is the most common cause of severe allergic reactions.
Allergy to peanut protein Ara h2, a very stable protein.
Allergy to Ara h8, cross reactivity with other foods. Not very stable
How do allergic reactions occur within a cell?
IgE is required for type I hypersensitivity.
B cells produce it when co-stimulated with IL-4 (secreted by TH2 cells)
