Podcast
Questions and Answers
Which type of hypersensitivity is mediated by antibodies?
Which type of hypersensitivity is mediated by antibodies?
What role do mast cells play in Type I hypersensitivity reactions?
What role do mast cells play in Type I hypersensitivity reactions?
What type of reaction is characterized by atopy?
What type of reaction is characterized by atopy?
Which of the following is NOT considered an atopic condition?
Which of the following is NOT considered an atopic condition?
Signup and view all the answers
In which year were the methods for defining hypersensitivity reactions proposed by Gell and Coombs?
In which year were the methods for defining hypersensitivity reactions proposed by Gell and Coombs?
Signup and view all the answers
What is the immediate effect of mast cell degranulation during an allergic reaction?
What is the immediate effect of mast cell degranulation during an allergic reaction?
Signup and view all the answers
Which lipid mediator is primarily responsible for bronchoconstriction during an allergic response?
Which lipid mediator is primarily responsible for bronchoconstriction during an allergic response?
Signup and view all the answers
What characterizes the early/immediate phase of an allergic reaction?
What characterizes the early/immediate phase of an allergic reaction?
Signup and view all the answers
What is a likely consequence of the late-phase response in an allergic reaction?
What is a likely consequence of the late-phase response in an allergic reaction?
Signup and view all the answers
What type of immune cell predominantly contributes to the late-phase allergic reaction?
What type of immune cell predominantly contributes to the late-phase allergic reaction?
Signup and view all the answers
What occurs during the second exposure to an allergen in individuals with sensitisation?
What occurs during the second exposure to an allergen in individuals with sensitisation?
Signup and view all the answers
Which mediator is synthesized de novo during the allergic response?
Which mediator is synthesized de novo during the allergic response?
Signup and view all the answers
Which statement correctly describes type V hypersensitivity?
Which statement correctly describes type V hypersensitivity?
Signup and view all the answers
What is a common clinical manifestation of Grave's disease?
What is a common clinical manifestation of Grave's disease?
Signup and view all the answers
What occurs when immune complexes are not cleared from the body?
What occurs when immune complexes are not cleared from the body?
Signup and view all the answers
Which factor is primarily associated with type III hypersensitivity reactions?
Which factor is primarily associated with type III hypersensitivity reactions?
Signup and view all the answers
In the context of type IIb hypersensitivity, what is the nature of the antibodies involved?
In the context of type IIb hypersensitivity, what is the nature of the antibodies involved?
Signup and view all the answers
Which antibody is primarily produced by B cells in response to T helper cell activation during allergic reactions?
Which antibody is primarily produced by B cells in response to T helper cell activation during allergic reactions?
Signup and view all the answers
What triggers the systemic release of vasoactive mediators in anaphylaxis?
What triggers the systemic release of vasoactive mediators in anaphylaxis?
Signup and view all the answers
What characterizes Goodpasture’s syndrome in terms of antibody involvement?
What characterizes Goodpasture’s syndrome in terms of antibody involvement?
Signup and view all the answers
Which of the following is NOT a typical cause of anaphylaxis?
Which of the following is NOT a typical cause of anaphylaxis?
Signup and view all the answers
What role do neutrophils play when antibodies bind to tissues during a type II hypersensitivity reaction?
What role do neutrophils play when antibodies bind to tissues during a type II hypersensitivity reaction?
Signup and view all the answers
What is a potential consequence of the complement system being activated in type II hypersensitivity reactions?
What is a potential consequence of the complement system being activated in type II hypersensitivity reactions?
Signup and view all the answers
Which of the following is a hallmark symptom of anaphylaxis?
Which of the following is a hallmark symptom of anaphylaxis?
Signup and view all the answers
Which environmental factors are associated with triggering Goodpasture's syndrome?
Which environmental factors are associated with triggering Goodpasture's syndrome?
Signup and view all the answers
What is a significant result of the systemic release of vasoactive mediators during anaphylaxis?
What is a significant result of the systemic release of vasoactive mediators during anaphylaxis?
Signup and view all the answers
What type of hypersensitivity reaction is mediated by IgG and IgM binding to antigens on cells or tissues?
What type of hypersensitivity reaction is mediated by IgG and IgM binding to antigens on cells or tissues?
Signup and view all the answers
Study Notes
MD137 Immunology - Lecture 4: Allergy & Autoimmunity
-
Learning Objectives:
- Understand allergy and autoimmunity.
- Identify four to five types of hypersensitivity reactions.
- Understand disease mechanisms.
- Give examples of each hypersensitivity type.
Hypersensitivity
- An excessive or inappropriate immune response causing tissue damage.
- 1963 Gell and Coombs classification method.
- Types I, II, III, and IV reactions distinguished by the mechanisms involved.
- Type I, II, III mediated by antibodies.
- Type IV mediated by T cells.
Type I Hypersensitivity (IgE-mediated allergy)
-
Immediate hypersensitivity response.
-
IgE produced by B cells.
-
Atopy: A tendency to produce IgE in response to allergens.
-
IgE binds to mast cell receptors.
-
Cross-linking of IgE by allergens triggers mast cell degranulation.
-
Release of mediators (e.g., histamine).
-
Atopic Conditions:
- Eczema
- Allergic rhinitis (hay fever)
- Asthma
- Food allergy
Type I Hypersensitivity - Sensitisation
- First exposure: Allergen causes IgE to bind to FcεRI receptors on mast cells.
- Second exposure: Cross-linking of IgE triggers mast cell degranulation, leading to allergy symptoms.
Mast Cell Mediators
-
Pre-formed mediators (stored in granules): Released within seconds
- Enzymes (tryptase, serotonin).
- Histamine.
-
Synthesized de novo: Released later
- Cytokines.
- Lipid mediators.
Lipid Mediators in Allergy
- Phospholipase A2, Arachidonate.
- Pathways for lipid mediator formation (12-HETE, 15-lipoxygenase and 5-lipoxygenase, Lipoxins A and B, Cyclooxygenase, Leukotrienes, etc)
- Outcomes or consequences of these mediators (bronchoconstriction, etc.)
Early/Immediate and Late-phase Reactions
- Early/immediate phase: Caused by primary mediators released from mast cells, occurring within minutes.
- Late phase: Infiltrating cells (eosinophils, neutrophils, T cells) release secondary mediators (cytokines, lipid mediators) 4-24 hours later.
- Long-term tissue damage (e.g., tissue remodeling) is a possible outcome.
Allergy Symptoms
- Symptoms depend on the affected tissue.
- Gastrointestinal tract: Increased fluid secretion, peristalsis, diarrhea, vomiting.
- Airways: Decreased diameter, increased mucus secretion, wheezing, coughing, phlegm.
- Blood vessels: Increased blood flow, permeability.
Type II Hypersensitivity (IgM/IgG-mediated)
- Caused by IgG or IgM binding to antigens on cells or tissues.
- Bound antibodies activate complement or bind to Fc receptors on phagocytes.
- Leads to cellular destruction, inflammation, or tissue damage.
- Example: Goodpasture's syndrome
Type III Hypersensitivity (Immune Complex-mediated)
- Caused primarily by IgG binding to soluble antigens.
- Immune complexes form, and if not cleared properly, they deposit in tissues.
- Can lead to inflammation, tissue damage, and vasculitis.
- Example: Systemic Lupus Erythematosus (SLE).
Type IV Hypersensitivity (T-cell mediated)
- Delayed-type hypersensitivity.
- T cell-driven, occurring after a delay (24-72 hours) compared to other hypersensitivity reactions.
- Includes contact dermatitis, multiple sclerosis, type 1 diabetes mellitus, and rheumatoid arthritis.
- Example: Contact hypersensitivity, Poison ivy.
Granulomatous Hypersensitivity
- Forms in response to persistent immune stimulation.
- Involves macrophages, other immune cells, and tissue inflammation.
- Examples: Crohn's disease and sarcoidosis.
Multiple Sclerosis (MS)
- Demyelination and sclerosis of nerve tissue (usually at multiple sites).
- T cells specific for myelin basic protein.
- Autoimmune disease affecting the central nervous system (CNS).
Grave's disease
- Autoimmune disease stimulating hormones.
- Antibodies mimic TSH binding, stimulating thyroid hormone release.
- Results in hyperthyroidism.
- Thyroid gland enlargement (goiter), weight loss, sweating, anxiety, exophthalmos.
Systemic Lupus Erythematosus (SLE)
- Autoantibodies against DNA and associated proteins.
- Systemic disease impacting various organs (kidneys, skin, lungs).
- Can cause kidney damage, butterfly rash, and pulmonary disease.
Summary of Main Points (repeated):
- Type I, IgE-mediated reactions.
- Type II, Antibody-mediated reactions.
- Type III, Immune complex-mediated reactions.
- Type IV, T-cell mediated reactions.
- Granulomatous hypersensitivity as a specific reaction pattern and chronic diseases, such as Crohn's disease and multiple sclerosis.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the concepts of allergy and autoimmunity in this quiz based on MD137 Immunology Lecture 4. Learn about the types of hypersensitivity reactions, their mechanisms, and examples of each type. Test your understanding of how the immune system responds to allergens.
