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Questions and Answers
What is the primary cause of allergic diseases?
What is the primary cause of allergic diseases?
What is the result of the immune response directed against self-antigens?
What is the result of the immune response directed against self-antigens?
What type of hypersensitivity reaction is caused by the release of mediators from mast cells?
What type of hypersensitivity reaction is caused by the release of mediators from mast cells?
What is the characteristic of Type II hypersensitivity reactions?
What is the characteristic of Type II hypersensitivity reactions?
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What is the result of the deposition of immune complexes in blood vessels?
What is the result of the deposition of immune complexes in blood vessels?
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What is the main difference between hypersensitivity reactions and normal immune responses?
What is the main difference between hypersensitivity reactions and normal immune responses?
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What is the role of immunoglobulin E antibodies in hypersensitivity reactions?
What is the role of immunoglobulin E antibodies in hypersensitivity reactions?
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What is the common characteristic of hypersensitivity reactions?
What is the common characteristic of hypersensitivity reactions?
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What type of hypersensitivity reaction is characterized by the activation of T lymphocytes specific for self antigens or microbes in tissues?
What type of hypersensitivity reaction is characterized by the activation of T lymphocytes specific for self antigens or microbes in tissues?
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What is the primary mechanism of immediate hypersensitivity reactions?
What is the primary mechanism of immediate hypersensitivity reactions?
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What is the estimated percentage of people affected by allergic diseases?
What is the estimated percentage of people affected by allergic diseases?
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What is the term for individuals who are prone to develop immediate hypersensitivity reactions?
What is the term for individuals who are prone to develop immediate hypersensitivity reactions?
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What is the role of Th2 cells in immediate hypersensitivity reactions?
What is the role of Th2 cells in immediate hypersensitivity reactions?
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What is the term for antigens that elicit immediate hypersensitivity reactions?
What is the term for antigens that elicit immediate hypersensitivity reactions?
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What is the outcome of late-phase reactions in immediate hypersensitivity?
What is the outcome of late-phase reactions in immediate hypersensitivity?
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What is the primary function of IgE antibodies in immediate hypersensitivity reactions?
What is the primary function of IgE antibodies in immediate hypersensitivity reactions?
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Study Notes
Allergy and Hypersensitivity
- Allergies are conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment.
- Common allergens include pollen and certain foods.
Hypersensitivity
- Hypersensitivity is a reflection of excessive or aberrant immune responses.
- Hypersensitivity reactions may occur in two situations:
- Responses to foreign antigens may cause tissue injury, especially if the reactions are repetitive or poorly controlled.
- The immune responses may be directed against self-antigens, as a result of the failure of self-tolerance.
Types of Hypersensitivity Reactions
- Type I: Immediate Hypersensitivity
- Caused by the release of mediators from mast cells.
- Depends on the production of immunoglobulin E (IgE) antibodies.
- Type II: Antibody-Mediated
- Antibodies directed against cell or tissue antigens can damage these cells or tissues or impair their function.
- Type III: Immune Complex Diseases
- Antibodies against soluble antigens in the blood may form complexes with the antigens, causing inflammation and tissue injury.
- Type IV: T cell-mediated diseases
- Some diseases result from the reactions of T lymphocytes specific for self-antigens or microbes in tissues.
Immediate Hypersensitivity
- Immediate hypersensitivity is an IgE antibody- and mast cell-mediated reaction to certain antigens.
- Causes rapid vascular leakage and mucosal secretions, often followed by inflammation.
- Allergy/Atopy: Disorders in which IgE-mediated immediate hypersensitivity is prominent.
- Atopic: Individuals with a propensity to develop these reactions.
Clinical Syndromes and Therapy
- Common types of immediate hypersensitivity:
- Hay fever
- Food Allergies
- Asthma
- Anaphylaxis
- Allergies are the most frequent disorders of the immune system, estimated to affect 10% to 20% of people.
- The incidence of allergic diseases has been increasing, especially in industrialized societies.
Development of Immediate Hypersensitivity Reactions
- Sequence of events includes:
- Activation of Th2 and IL-4-secreting follicular helper T (Tfh) cells.
- Binding of IgE to IgE-specific Fc receptors of mast cells.
- Cross-linking of the bound IgE by the antigen.
- During this event, mast cells mediators cause a rapid increase in vascular permeability and smooth muscle contraction.
- Immediate reactions may occur in minutes.
- Late-phase reactions happen when mast cells continuously recruit neutrophils and eosinophils over several hours, causing tissue injury.
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Description
Discover the different types of hypersensitivity reactions, including immediate hypersensitivity, and learn about clinical syndromes and therapy. Explore the causes of allergies and common allergens.
