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Questions and Answers
What does atopy refer to in medical terms?
What does atopy refer to in medical terms?
What percentage of the population in developed countries is estimated to be atopic?
What percentage of the population in developed countries is estimated to be atopic?
What is the primary characteristic of hives (urticaria)?
What is the primary characteristic of hives (urticaria)?
What does the term 'asthma' literally mean?
What does the term 'asthma' literally mean?
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What is a potential consequence of anaphylaxis if left untreated?
What is a potential consequence of anaphylaxis if left untreated?
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What percentage of Canadians are affected by seasonal allergic rhinitis (hay fever)?
What percentage of Canadians are affected by seasonal allergic rhinitis (hay fever)?
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Food allergies impact which percentage of Canadians?
Food allergies impact which percentage of Canadians?
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Which insects are most commonly associated with allergic reactions?
Which insects are most commonly associated with allergic reactions?
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What type of allergic reaction is asthma most commonly associated with?
What type of allergic reaction is asthma most commonly associated with?
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What has been the trend in allergy prevalence over the last 30 years?
What has been the trend in allergy prevalence over the last 30 years?
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Which type of hypersensitivity reaction is primarily mediated by IgE antibodies?
Which type of hypersensitivity reaction is primarily mediated by IgE antibodies?
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What characterizes Type II hypersensitivity reactions?
What characterizes Type II hypersensitivity reactions?
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Which statement accurately describes the immunological mechanisms of Type III hypersensitivity reactions?
Which statement accurately describes the immunological mechanisms of Type III hypersensitivity reactions?
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What does sensitization to an antigen entail in the context of hypersensitivity reactions?
What does sensitization to an antigen entail in the context of hypersensitivity reactions?
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Which of the following correctly identifies a common feature shared by all types of hypersensitivity reactions?
Which of the following correctly identifies a common feature shared by all types of hypersensitivity reactions?
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Which type of hypersensitivity is specifically associated with delayed-type mechanisms?
Which type of hypersensitivity is specifically associated with delayed-type mechanisms?
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What is an allergen?
What is an allergen?
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What role do memory responses play in hypersensitivity reactions?
What role do memory responses play in hypersensitivity reactions?
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Which is an example of a Type I hypersensitivity reaction?
Which is an example of a Type I hypersensitivity reaction?
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How can the antigen involved in hypersensitivity be characterized?
How can the antigen involved in hypersensitivity be characterized?
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Study Notes
Hypersensitivity Reactions Overview
- Hypersensitivity reactions (HSRs) are heightened immune responses to antigens, potentially harmful or fatal.
- Gell & Coombs classification categorizes HSRs into four types (I-IV).
- Type I: Allergy/anaphylaxis/atopic reactions
- Type II: Antibody-mediated, antibodies bind to cells/tissues.
- Type III: Immune complex-mediated, involves IgG and soluble antigens.
- Type IV: Delayed-type hypersensitivity (DTH), cell-mediated via T-cells and macrophages.
Common Features of Hypersensitivity Reactions
- Adaptive immune response, involves sensitization to the antigen (primary response).
- Memory response develops, can last for years.
- Antigens are often proteins (or haptens/drugs conjugated with proteins).
Type I Hypersensitivity Reactions (Immediate Hypersensitivity)
- Characterized by immediate reactions due to IgE antibodies.
- Triggers include allergens (innocuous antigens), typically proteins initiating IgE responses.
- Atopic individuals ( ~40% of developed world population) are more prone to IgE mediated responses.
- Recent data shows a 2-3 fold increase in allergy occurrence in the last 30 years.
- Conditions associated with type I include:
- Allergic asthma (studied as a case example)
- Seasonal allergic rhinitis ("hay fever")
- Food allergies (affecting ~6-8% of Canadians)
- Reactions to insect stings (bees, wasps, yellow jackets)
- Hives (urticaria)
Key Terms
- Allergy: Altered reactivity to an antigen.
- Allergen: Antigen causing allergic reaction.
- Atopy: Tendency to develop IgE-mediated antibodies to allergens.
- Asthma: Chronic respiratory condition, often allergic in nature.
- Anaphylaxis: Exaggerated systemic allergic reaction, potentially fatal.
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Description
This quiz covers the classification and key features of hypersensitivity reactions, including Gell & Coombs classification types I-IV. Explore the mechanisms of each type, from immediate allergic responses to delayed-type hypersensitivity. Test your knowledge on how these immune responses can vary and their implications on health.
