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Questions and Answers
What characterizes hypersensitivity reactions?
What can result from a failure of self-tolerance mechanisms?
What is a significant feature of hypersensitivity diseases?
In a population, what percentage may be abnormally responsive to environmental substances?
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What is one of the consequences of excessive immune reactions against microbes?
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Which type of antibody is primarily associated with allergic diseases in hypersensitive individuals?
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Which of the following statements is accurate regarding humoral and cell-mediated immunities in hypersensitivity?
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What is the primary distinction between types of hypersensitivity reactions?
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What characterizes hormone production in patients with Graves’ disease?
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What is the main effect of autoantibodies in myasthenia gravis?
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Which mechanism is NOT involved in the destruction of RBCs in autoimmune hemolytic anemia?
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How do antibodies function as antagonists in the context of cell-surface receptors?
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What type of antibodies are generally involved in cell- or tissue-specific diseases?
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What results from the binding of autoantibodies to acetylcholine receptors in myasthenia gravis?
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In autoimmune hemolytic anemia, which receptor type contributes to RBC destruction through opsonization?
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Which statement about the mechanisms of autoreactive antibodies is true?
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What characterizes the immune response in allergic diseases compared to autoimmune diseases?
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What is the role of autoantibodies that act as receptor antagonists?
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In which condition do autoantibodies against the TSH receptor lead to excessive thyroid hormone production?
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Which type of hypersensitivity reaction is uniquely associated with allergic diseases?
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How do autoantibodies against streptococcal antigens contribute to rheumatic fever?
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What is a common mechanism by which autoantibodies mediate disease in autoimmune disorders?
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What effect does the binding of autoantibodies (agonists) to the TSH receptor have in Graves’ disease?
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What are the main similarities between the mechanisms of allergic reactions and autoimmune diseases?
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What is the primary mechanism of tissue injury in immune complex-mediated diseases?
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In Goodpasture's syndrome, what is observed in immunofluorescence?
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Which type of immune response is primarily responsible for tissue injury in T cell-mediated diseases?
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Which statement about immune complex-mediated diseases is true?
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What type of inflammation is seen in glomerulonephritis associated with systemic lupus erythematosus (SLE)?
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How do T lymphocytes typically cause tissue injury?
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What characterizes the inflammation associated with antibody-mediated glomerulonephritis?
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In the context of immune complex-mediated diseases, what could promote the recruitment of neutrophils?
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How can humans be sensitized for delayed-type hypersensitivity (DTH) reactions?
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What is the primary purpose of the purified protein derivative (PPD) in relation to tuberculosis?
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In a positive tuberculin skin test response, what indicates prior exposure to tuberculosis?
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What autoimmune characteristic is commonly observed in patients with rheumatoid arthritis?
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What is a common goal of current treatments for autoimmune diseases?
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In terms of hypersensitivity reactions, which type of hypersensitivity is exemplified by the tuberculin reaction?
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Which factor does NOT contribute to DTH reactions according to the given information?
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Which of the following statements about cytokine antagonists is most accurate?
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Study Notes
Hypersensitivity Reactions
- Hypersensitivity refers to harmful immune responses against foreign antigens like environmental substances, drugs, and microbes.
- In healthy individuals, there is no reaction towards harmless environmental substances, but 20% of the population may be abnormally responsive to one or more of these substances.
- Hypersensitivity reactions are classified based on the type of immune response, the mechanism responsible for cell and tissue injury, and the effector mechanism.
- Reactions can be antibody-dependent or T cell-dependent.
Classification of Hypersensitivity
- Type I: IgE-mediated, involves allergic reaction involving mast cells and basophils.
- Type II: Antibody-dependent cytotoxic reactions, involves antibodies binding to cell surface antigens.
- Type III: Immune complex-mediated reactions, involves the formation of immune complexes that deposit in tissues and activate complement.
- Type IV: Cell-mediated reactions, involves T cell-mediated responses.
Autoimmunity
- Occurs when immune system reacts against self-antigens, causing autoimmune diseases.
- Breakdown in self-tolerance mechanisms leads to T and B cell mediated responses.
- Examples: rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis.
Antibody-Mediated Diseases
- Antibodies act as either agonists or antagonists.
- Agonists mimic the natural ligand and activate the receptor.
- Antagonists block the natural ligand and inhibit receptor activation.
Examples of Antibody-Mediated Diseases
- Graves' disease: AutoAbs against TSH receptor, cause overproduction of thyroid hormones.
- Myasthenia gravis: AutoAbs against acetylcholine receptor, decrease muscle contraction efficiency.
- Autoimmune hemolytic anemia: Antibodies target red blood cells, leading to their destruction.
- Glomerulonephritis: Antibodies target glomerular basement membrane, causes inflammation and damage.
Immune Complex-Mediated Diseases
- Involve immune complexes formed in circulation and deposited in tissues.
- Immune complexes usually composed of antibodies against self-antigens or foreign antigens.
- Primarily affect multiple organs, but sometimes they affect the kidneys.
- Examples: Systemic Lupus Erythematosus (SLE).
Cell-Mediated Diseases
- T lymphocytes can cause tissue damage through cytokine production or direct killing of target cells.
- CD4+ T cells mainly contribute to inflammation, while CD8+ CTLs kill cells.
- T cells involved can be autoreactive or specific for foreign antigens present in tissues.
Examples of Cell-Mediated Diseases
- Contact hypersensitivity: Response to environmental antigens, like poison ivy.
- Tuberculin reaction: Delayed-type Hypersensitivity (DTH) response to Mycobacterium tuberculosis antigens.
Treatment of Immunologic Diseases
- Focus on reducing immune activation and the injurious consequences of the autoimmune response.
- Therapeutic approaches include cytokine antagonists and monoclonal antibodies.
Pathogenesis of Autoimmune Diseases
- Systemic lupus erythematosus (SLE): Involves the production of autoantibodies against various components of the nucleus, resulting in tissue inflammation and damage.
- Rheumatoid arthritis (RA): Involves the production of autoantibodies against the Fc region of IgG, known as rheumatoid factor.
Treatment of Rheumatoid Arthritis
- Current treatment focuses on reducing immune activation and inflammation.
- TNF-α inhibitors have shown significant success in managing RA symptoms.
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Description
This quiz covers the fundamental concepts of hypersensitivity reactions, including their classification and mechanisms. You'll learn about the four types of hypersensitivity reactions and how immune responses can lead to harmful effects. Ideal for students studying immunology or related fields.