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Questions and Answers
What is the first stage that an allergy undergoes when the immune system encounters an allergen?
What is the first stage that an allergy undergoes when the immune system encounters an allergen?
Which immune cells are primarily involved in the degranulation process during an allergic reaction?
Which immune cells are primarily involved in the degranulation process during an allergic reaction?
Which of the following describes the physiological response during the reactive phase of an allergy?
Which of the following describes the physiological response during the reactive phase of an allergy?
What typical symptoms are associated with inflammation during an allergic response?
What typical symptoms are associated with inflammation during an allergic response?
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Which antibody plays a critical role in mediating allergic reactions?
Which antibody plays a critical role in mediating allergic reactions?
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What primary factor affects the severity of an allergic response?
What primary factor affects the severity of an allergic response?
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Which characteristic differentiates parasitic antigens from allergens?
Which characteristic differentiates parasitic antigens from allergens?
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What type of allergic reaction is characterized by symptoms like hives and redness?
What type of allergic reaction is characterized by symptoms like hives and redness?
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Which cells are involved in amplifying an allergic response?
Which cells are involved in amplifying an allergic response?
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What causes lower blood pressure during anaphylaxis?
What causes lower blood pressure during anaphylaxis?
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Which of the following is NOT a symptom of anaphylaxis?
Which of the following is NOT a symptom of anaphylaxis?
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What dictates the type of allergic reaction experienced?
What dictates the type of allergic reaction experienced?
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What are the components involved in the symptoms of hives?
What are the components involved in the symptoms of hives?
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What is the primary role of IgE in the immune response?
What is the primary role of IgE in the immune response?
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What genetic factor is primarily involved in increasing the risk of allergies?
What genetic factor is primarily involved in increasing the risk of allergies?
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Which type of immune cell is primarily associated with allergy responses?
Which type of immune cell is primarily associated with allergy responses?
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How does IL-4 affect T-cell differentiation?
How does IL-4 affect T-cell differentiation?
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What is the outcome of the immune response during an allergic reaction?
What is the outcome of the immune response during an allergic reaction?
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Which cytokines are overexpressed in individuals predisposed to allergies?
Which cytokines are overexpressed in individuals predisposed to allergies?
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What triggers the class switching of B-cells to produce IgE?
What triggers the class switching of B-cells to produce IgE?
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What role do mast cells play in the immune reaction associated with allergies?
What role do mast cells play in the immune reaction associated with allergies?
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What is the primary aim of the gastrointestinal response to infection?
What is the primary aim of the gastrointestinal response to infection?
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What is NOT a function of leukotrienes and prostaglandins during a gastrointestinal reaction?
What is NOT a function of leukotrienes and prostaglandins during a gastrointestinal reaction?
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Which of the following methods is commonly used to identify potential allergens?
Which of the following methods is commonly used to identify potential allergens?
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What does serum IgE concentration indicate about an individual?
What does serum IgE concentration indicate about an individual?
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Which factor is NOT considered when determining the severity of an allergic reaction?
Which factor is NOT considered when determining the severity of an allergic reaction?
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Anaphylaxis is characterized by which of the following responses?
Anaphylaxis is characterized by which of the following responses?
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What is the role of specific epitopes in allergy management?
What is the role of specific epitopes in allergy management?
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In the context of allergy diagnosis, why is the skin prick test significant?
In the context of allergy diagnosis, why is the skin prick test significant?
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Study Notes
Hypersensitivity Type I: Allergy
- Allergy is a misdirected immune response to a non-threatening antigen.
- Allergy escalates the immune response to cause a large immune reaction.
- Allergy has genetic factors that increase the number and reaction potential towards Th2 cells and IgE antibody response.
Predisposition to Allergy (Atopy)
- Rates of allergy are increasing in Western populations, reaching 40%.
- Allergy is caused by a propensity towards an immune response involving IgE and Th2 cells.
- Class switching to IgE in B cells is a key aspect.
- Th2 cells increase, resulting in two interactions: T-cell differentiation to Th2 cells and B-cells switching to IgE.
- Overexpression of IL-4, 5, 9, and 13, requiring GATA-3 Transcription Factor, is observed.
Mechanisms of Allergy
- Sensitization: Initial encounter with allergen creates an immune response that's not overly misdirected.
- Reactive Phase: Subsequent encounters trigger immunological and physiological responses, including inflammatory signs (rubor, calor, dolor, tumor, loss of function).
IgE Production
- Th2 cells and naïve B cells interact with CD40, CD40L, and IL-13.
- IgE is locally produced in germinal centers of lymph nodes.
- IgE receptors (IgER) are found on basophils, eosinophils, and mast cells.
- Positive feedback loops intensify IgE response until the threat is neutralized.
Causes of Degranulation in Immune Cells
- Mast cells release histamine, interleukins, and lipid mediators (leukotrienes, prostaglandins, PAF).
- The aim of these releases is to attract and activate other immune cells.
- The outcome of the cascade is an exponential response to stimuli leading to inflammatory responses.
Symptoms of Allergy
- Tumour: Localized inflamed area with a central flare.
- Rubor: Red inflammation surrounding the flare.
- Dolor/Calor: Painful and often itchy, warm, inflamed area.
- Loss of function: Primarily seen in digestive and respiratory tracts.
- Inflammation is the primary source of symptoms through several pathways (examples given in presentation)
Types of Allergic Reaction
- Anaphylaxis: A centralized allergic response.
- Allergic rhinitis: Symptoms include sneezing and coughing.
- Diarrhoea and vomiting: Gastrointestinal reaction.
- Allergic dermatitis (hives): Skin reaction manifest with hives.
- What determines the type of reaction, and factors include the concentration /site of allergen.
Comparison of Allergens vs. Parasitic Antigens
- Protein allergens are present in higher doses, have low molecular weight (10-40 kDa), are highly soluble, stable, and bind to MHC class II.
- Parasitic antigens are present in lower doses, have low molecular weight (10-40 kDa), are highly soluble, have short-acting stability, and mainly bind to MHC class II.
Severity of Allergic Responses
- High allergen and IgE doses lead to high responses.
- Amplification of response by mast cells, eosinophils, and basophils.
- Location of activating nodes dictates location and type of response.
Diagnosis of Allergy
- Clinicians look for the cause of the reaction, causative substances, specific epitopes, and predict symptom severity.
- Identifying disease episodes through food diaries (but not ideal for anaphylaxis) is crucial.
- Skin prick tests and epitope determination (e.g., Der-P1, PR-10, BSA) help identify specific triggers.
- Serum IgE levels correlate with likelihood and severity of allergic reactions..
Determination of Severity
- Clinicians need to consider factors like previous reactions; epitope stability and ubiquity; and site of absorption to determine the severity.
Summary
- The presentation highlights the intricate relationship between immune cells, allergens, and resultant reactions.
- Different types of allergic reactions affect various parts of the body.
- The role of laboratories in allergy diagnosis and patient care is crucial, providing vital information.
- Clinicians and the laboratory collaborate in providing accurate diagnoses and effectively managing patient care.
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Description
Explore the mechanisms and genetics behind Type I hypersensitivity in allergies. This quiz covers topics such as genetic predisposition, sensitization, and the roles of IgE and Th2 cells. Understand the processes that lead to allergic reactions and their implications.
