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Questions and Answers
Which type of hypersensitivity reaction is primarily associated with IgE antibodies?
Which type of hypersensitivity reaction is primarily associated with IgE antibodies?
Which condition is commonly categorized under Type II hypersensitivity reactions?
Which condition is commonly categorized under Type II hypersensitivity reactions?
What type of hypersensitivity reaction is characterized by immune complexes?
What type of hypersensitivity reaction is characterized by immune complexes?
Koch's phenomenon is an example of which type of hypersensitivity reaction?
Koch's phenomenon is an example of which type of hypersensitivity reaction?
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Which diagnosis method is employed to identify allergies in patients?
Which diagnosis method is employed to identify allergies in patients?
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What can result from exposure to normally sequestered antigens during development?
What can result from exposure to normally sequestered antigens during development?
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How can structural modification of tissue proteins lead to autoimmune disease?
How can structural modification of tissue proteins lead to autoimmune disease?
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What does cross-reactivity refer to in the context of autoimmune diseases?
What does cross-reactivity refer to in the context of autoimmune diseases?
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What is an example of an autoimmune disease caused by the modification of surface proteins?
What is an example of an autoimmune disease caused by the modification of surface proteins?
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What is the primary mechanism behind autoimmune diseases resulting from exposure to normally hidden antigens?
What is the primary mechanism behind autoimmune diseases resulting from exposure to normally hidden antigens?
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What characterizes type IV hypersensitivity?
What characterizes type IV hypersensitivity?
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In immune complex-mediated hypersensitivity, what is a primary mechanism of tissue damage?
In immune complex-mediated hypersensitivity, what is a primary mechanism of tissue damage?
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What is the typical time frame for reactions in type I hypersensitivity?
What is the typical time frame for reactions in type I hypersensitivity?
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Which of the following describes the role of macrophages in delayed hypersensitivity reactions?
Which of the following describes the role of macrophages in delayed hypersensitivity reactions?
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Which immunological response is characterized by the presence of serum sickness and systemic lupus erythematosus (SLE)?
Which immunological response is characterized by the presence of serum sickness and systemic lupus erythematosus (SLE)?
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What is the hallmark of autoimmune diseases related to autotolerance failure?
What is the hallmark of autoimmune diseases related to autotolerance failure?
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What type of hypersensitivity is characterized by complement activation and cell destruction via antibodies?
What type of hypersensitivity is characterized by complement activation and cell destruction via antibodies?
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What is a major characteristic of the Arthus reaction?
What is a major characteristic of the Arthus reaction?
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Which of the following best describes acquired (induced) tolerance?
Which of the following best describes acquired (induced) tolerance?
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Which cell type is primarily involved in type III hypersensitivity reactions?
Which cell type is primarily involved in type III hypersensitivity reactions?
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Study Notes
Hypersensitivity Reactions and Autoimmunity
- Hypersensitivity reactions are harmful immune responses to a harmless antigen.
- Autoimmunity is a breakdown in tolerance where the immune system attacks its own body's cells.
Lecture Outline
- Hypersensitivity reactions
- Autoimmune diseases and tolerance
Lecture Learning Objectives
- Understand Hypersensitivity reactions
- Understand autoimmune diseases and tolerance
Immunopathogenesis
- Immunopathogenesis is the study of the disease mechanisms of hypersensitivity reactions.
Gell and Coombs Classification of Hypersensitivity Reactions
| Type | Examples | Mechanism |
|---|---|---|
| I | Anaphylaxis, asthma, hay fever, eczema, food allergies | IgE |
| II | HTR caused by ABO incompatibility, HDN caused by Rh incompatibility | Cytotoxic Ab |
| III | Serum sickness, Arthus phenomenon, rheumatoid arthritis | Immune complexes |
| IV | Koch's phenomenon, allograft rejection, contact dermatitis | Cell-mediated |
Type I Hypersensitivity Reactions
- Allergen triggers the production of IgE antibodies, binding to mast cells.
- Subsequent exposure to allergen leads to mast cell degranulation and release of vasoactive amines.
- This results in a range of symptoms, including inflammation and tissue damage.
- The process is regulated by CD4 cells and IL-4.
IgE-mediated Allergic Reactions
- This table describes common allergens, their routes of entry, and resulting symptoms in IgE-mediated allergic reactions.
| Syndrome | Allergen(s) | Route(s) of entry | Response |
|---|---|---|---|
| Systemic anaphylaxis | Drugs, serum, venoms, peanuts | IV (injection to tissue) | Increased vascular permeability, edema, tracheal occlusion, circulatory collapse, and death |
| Wheal and flare | Insect bites, Allergy testing | Subcutaneous | Local increase in blood flow and vascular permeability |
| Allergic rhinitis (hay fever) | Pollens, dust-mite feces | Inhaled | Edema of nasal mucosa, irritation of nasal mucosa |
| Bronchial asthma | Pollens, dust mite feces | Inhaled | Bronchial constriction, increased mucus production, airway inflammation |
| Food allergy | Shellfish, Milk, Eggs, Fish, Wheat | Oral | Vomiting, diarrhea, pruritis, urticaria, anaphylaxis |
Skin Prick Test for Allergy Diagnosis
- Introducing a low dose allergen into skin to detect immediate hypersensitivity reactions.
Drug Hypersensitivity
- A series of hypersensitivity reactions triggered by medication, including skin rashes, inflammation, and other symptoms.
Erythema Nodosum Lesions
- Skin lesions due to hypersensitivity to Coccidioides immitis antigens .
Bite Reactions
- Skin reactions, appearing as multiple linearly arranged erythematous nodules, with tense blister formation.
Hives (Urticaria)
- Skin rashes, characterized by red, raised, itchy areas.
Type II Cytotoxic Mechanism
- Antibodies bind to target cells, leading to their destruction by complement activation or phagocytosis.
Immune Complex-Mediated Hypersensitivity
- Immune complexes (antigen-antibody complexes) deposit in tissues, activating complement and attracting inflammatory cells.
- Resulting inflammation and tissue damage are characteristic of this type of hypersensitivity. This can lead to many issues.
Mechanisms of Damage in Immune Complex Hypersensitivity
- Immune complexes are formed from antigen and antibody, aggregated platelets are involved, and complement is activated.
- Vasoactive amines are released, microthrombi form, and enzymes are released.
- This leads to inflammation, tissue damage, and other complications.
Immune Complex Hypersensitivity
- Immunopathological responses due to the formation of immune complexes in tissues, resulting in various diseases.
Immunopathogenesis/ Tolerance and Autoimmunity
- Discusses tolerance to self-antigens; when tolerance to outside antigens is required, which can cause issues like autoimmune diseases.
Definition of Tolerance
- The body's ability to not attack its own cells, meaning it doesn't attack its own self-antigens. This has two aspects:
- Auto-tolerance (natural tolerance of self-antigens).
- Acquired tolerance (induced tolerance of outside antigens).
Autotolerance
- Tolerance to self-antigens, induced early in development, mainly in utero. Failure can cause autoimmune diseases.
Acquired (Induced Tolerance)
- Induction of tolerance to an antigen throughout life. This is important for allergy treatment, immune response to an antigen, and graft rejection.
Definition of Autoimmune Disease
- Adaptive immune response to self-antigens, leading to the production of autoantibodies and/or self-reactive T-cells, resulting in autoimmune diseases.
Aetiology of Autoimmune Diseases (Causes)
- Exposure to sequestered antigens:
- Antigens not usually exposed to the immune system during development, but exposed for example by injury to these areas, will trigger an immune response
- Structural modification of tissue proteins:
- Certain drugs, chemicals or viruses can alter protein structures on tissues.
- These proteins are no longer recognized by the body as self and the immune system will initiate an attack leading to autoimmune diseases.
- Cross-reactivity:
- Antibodies produced against one antigen can react with similar antigens on other tissues, which is known as cross-reactivity.
- This leads to the body attacking its own tissues instead of the foreign antigen.
Genetic Predisposition to Autoimmune Disease
- Genetic factors play a role
- Some autoimmune diseases run in families
- This may be linked to specific MHC antigens, which are capable of presenting self peptides to self-reactive cells.
- Several autoimmune diseases exhibit strong associations with specific MHC proteins.
Mechanisms of Tissue Injury in Autoimmune Disease
- Type II: Cytotoxic reactions
- Type III: Immune-complex-mediated reactions
- Type IV: Cell-mediated reactions
Ulcerative Colitis
- A form of inflammatory bowel disease.
Lab Diagnosis of Autoimmune Diseases
- Elevated serum immunoglobulins
- Presence/detection of autoantibodies
- Detection of immune complexes in serum and tissues
- Level of complement in serum
Management of Autoimmune Diseases
- Anti-inflammatory drugs
- Immunosuppressive drugs
- Plasmapheresis
- Interference with cytokine network
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Description
This quiz covers hypersensitivity reactions and autoimmune diseases, exploring the mechanisms and classifications involved. Gain insights into how the immune system can react harmfully to harmless antigens and the breakdown of tolerance that leads to autoimmunity.
