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Questions and Answers
What is the role of IL-5 in the immune response?
What is the role of IL-5 in the immune response?
Which phase occurs first during a Type I hypersensitivity reaction?
Which phase occurs first during a Type I hypersensitivity reaction?
What happens during the immediate effector phase of allergic reactions?
What happens during the immediate effector phase of allergic reactions?
Which of the following statements about FceRI is correct?
Which of the following statements about FceRI is correct?
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How do mast cells and basophils contribute to IgE-mediated responses?
How do mast cells and basophils contribute to IgE-mediated responses?
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What is the function of Th2 cells in the immune response?
What is the function of Th2 cells in the immune response?
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During which phase are allergens processed and presented to T cells?
During which phase are allergens processed and presented to T cells?
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Which type of immunoglobulin is primarily involved in allergic reactions?
Which type of immunoglobulin is primarily involved in allergic reactions?
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What is the primary role of IgE antibodies in type I hypersensitivity reactions?
What is the primary role of IgE antibodies in type I hypersensitivity reactions?
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Which type of T helper cell is primarily involved in the activation of IgE responses in allergic reactions?
Which type of T helper cell is primarily involved in the activation of IgE responses in allergic reactions?
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What is a major consequence of mast cell degranulation during an allergic reaction?
What is a major consequence of mast cell degranulation during an allergic reaction?
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Which symptom is typically associated with an allergic reaction mediated by type I hypersensitivity?
Which symptom is typically associated with an allergic reaction mediated by type I hypersensitivity?
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How can allergies be diagnosed in individuals?
How can allergies be diagnosed in individuals?
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Which type of immune response does type II hypersensitivity relate to?
Which type of immune response does type II hypersensitivity relate to?
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What type of antigens are classified as allergens in type I hypersensitivity reactions?
What type of antigens are classified as allergens in type I hypersensitivity reactions?
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What is a characteristic feature of mast cells that contribute to their role in allergic responses?
What is a characteristic feature of mast cells that contribute to their role in allergic responses?
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What role do mast cells play in allergic reactions?
What role do mast cells play in allergic reactions?
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Which cytokine is primarily responsible for recruiting eosinophils during an allergic reaction?
Which cytokine is primarily responsible for recruiting eosinophils during an allergic reaction?
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IgE-mediated responses are primarily associated with which type of allergic conditions?
IgE-mediated responses are primarily associated with which type of allergic conditions?
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What is a significant effect of eosinophil activation during allergic reactions?
What is a significant effect of eosinophil activation during allergic reactions?
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What symptom is commonly associated with allergic rhinitis?
What symptom is commonly associated with allergic rhinitis?
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Which of the following conditions is NOT typically classified as a Type I allergic reaction?
Which of the following conditions is NOT typically classified as a Type I allergic reaction?
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What is the primary mechanism by which mast cells mediate allergic reactions?
What is the primary mechanism by which mast cells mediate allergic reactions?
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Which type of cell is primarily activated by IL-5 during an allergic reaction?
Which type of cell is primarily activated by IL-5 during an allergic reaction?
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Study Notes
Hypersensitivity Reactions
- Immune reactions triggered by non-pathogen antigens, occurring on subsequent exposures to a sensitized individual.
- Allergies and immune conditions cause excessive side effects destroying host tissues (inflammation).
- Drives allergic or atopic responses, not autoimmune.
Type I Hypersensitivities
- IgE on FceRI receptors bind soluble antigens (allergens), causing degranulation of mast cells, basophils, and eosinophils.
- Histamine leads to inflammation.
Hypersensitivity Differences
- Type II: IgG binds to cell-associated antigens or receptors, activating complement or altering signalling.
- Type III: IgG binds to soluble foreign proteins forming immune complexes, which deposit in tissues.
- Type IV: CD4 Th1 cells and CD8 cytotoxic T cells respond to foreign/modified self-proteins.
Autoimmunity
- Adaptive immune responses directed at healthy host cells and tissues (types II, III, and IV).
- Immune system mistakenly targets the body's own cells.
Allergens
- Antigens that elicit allergic/atopic responses (type I).
- Small, soluble, dried proteins that rehydrate on contact with mucus, releasing antigens.
Mast Cells
- Primary responders in allergic reactions.
- Release histamine and TNF-α to induce allergic inflammation.
- When IgE binds to FceRI, histamine and TNF-α release causes leaky capillaries, recruiting immune cells.
Eosinophils
- Granulocytes in mucosal and epithelial tissues.
- Long-lived, retain memory for antigens.
- Secondary responders in late effector phase.
- Release toxic granules.
- Found in respiratory, GI, and GU tracts.
Basophils
- Secondary responders; recruited to inflamed tissues.
- Activated via TLRs.
- Secrete IL-4 and IL-13, which influence T cell differentiation and IgE switching.
FceRI
- Receptor with high affinity for IgE on mast cells and basophils.
- Cross-linking results in degranulation.
Phases of Type I Hypersensitivity
- Sensitization Phase: Initial allergen exposure triggers T cell differentiation into Th2 cells, stimulating IgE production against the specific allergen.
- Immediate Effector Phase: Re-exposure leads to cross-linking of IgE on mast cells, causing immediate degranulation and release of pre-formed mediators like histamine and TNF-α.
- Late Effector Phase: Mast cells release lipid factors (PAF), leukotrienes, and prostaglandins causing more potent effects. Th2 cells are further activated.
Allergic Reaction Effects
- Gastrointestinal tract: Increased fluid secretion, diarrhea, vomiting.
- Airways: Constriction, mucus production, coughing, sneezing.
- Blood vessels: Increased permeability, edema, inflammation.
Allergy vs Intolerance
- Allergy: IgE-mediated response (anaphylaxis, urticaria).
- Intolerance: Not IgE-mediated (asthma).
Type I Diagnoses
- Allergic Rhinitis
- Atopic/Allergic Asthma
- Urticaria
- Angioedema
- Atopic Dermatitis (eczema)
- Systemic Anaphylaxis
Predisposing Factors
- A combination of genes and environmental factors.
- Exposure to various environmental factors can influence susceptibility to certain conditions.
Purpose of IgE-mediated Responses
- Protect against helminths/parasites too large to be phagocytosed.
Hygiene Hypothesis
- Developed countries have increased incidence of atopic disorders.
- Limited exposure to pathogens during childhood might contribute to immune system development, potentially influencing susceptibility to conditions like allergies.
Treatments for Atopic Disorders
- Avoiding allergens is a common treatment approach.
- Managing symptoms with medications.
- In some cases, allergen immunotherapy (desensitization) is employed.
Pharmacological Treatments
- Immunological: Desensitization with allergen-specific immunotherapy (SIT).
- Helminthic therapy aims to induce parasite-specific IgE response, potentially influencing allergic responses.
- Antihistamines block histamine binding to H1 receptors, mitigating effects.
- Monoclonal anti-IgE blocks IgE from binding to Fc receptors.
- Lipoxygenase antagonists prevent leukotriene generation.
- Corticosteroids and epinephrine manage inflammation and allergic reactions, respectively.
Skin Conditions
- Urticaria, hives.
- Angioedema, swelling.
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Description
Explore the different types of hypersensitivity reactions, including Type I, II, III, and IV, and how they interact with the immune system. Understand the role of antibodies like IgE and IgG, and how these reactions can lead to various allergic responses and autoimmunity. This quiz will challenge your knowledge of immunological processes and their implications.
