Tolerance and Autoimmune Disorders
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Questions and Answers

What are the two major types of hypersensitivity reactions involved in autoimmune diseases?

Type II and Type III hypersensitivity reactions.

Describe the chronic nature of autoimmune diseases.

Autoimmune diseases are chronic and progressive, characterized by relapses and remissions.

What factors can influence the signs and symptoms of autoimmune diseases?

Age, hormones, and environmental factors can influence symptoms.

Name a common organ-specific autoimmune disease related to the thyroid.

<p>Grave's disease or Hashimoto thyroiditis.</p> Signup and view all the answers

Identify a systemic autoimmune disease and mention its implication.

<p>Systemic lupus erythematosus, which affects multiple organs throughout the body.</p> Signup and view all the answers

How do the clinical manifestations of autoimmune diseases impact their classification?

<p>Clinical manifestations are overlapping and affect classification, complicating accurate diagnosis.</p> Signup and view all the answers

What role do autoreceptor antibodies play in autoimmune conditions?

<p>Autoreceptor antibodies can interfere with normal cellular functions, as seen in Myasthenia gravis.</p> Signup and view all the answers

What is a significant characteristic of an individual with autoimmune diseases?

<p>An individual may have more than one autoimmune disease simultaneously.</p> Signup and view all the answers

Which organs are commonly impacted by autoimmune diseases?

<p>Blood vessels, connective tissues, joints, muscles, skin, and endocrine glands.</p> Signup and view all the answers

What distinguishes organ-specific from systemic autoimmune diseases?

<p>Organ-specific diseases target individual organs, while systemic diseases affect multiple body systems.</p> Signup and view all the answers

What leads to the breakdown of T cell anergy and the subsequent activation of T cells specific for self-antigens?

<p>The upregulation of costimulatory molecules on antigen-presenting cells (APCs) causes the breakdown of T cell anergy and activates T cells.</p> Signup and view all the answers

How can molecular mimicry result in autoimmune reactions?

<p>Molecular mimicry occurs when a microbe shares an amino acid sequence with a self-antigen, leading to cross-reactive immunological reactions that target self-antigens.</p> Signup and view all the answers

What role do polyclonal B cell activation play in autoimmunity?

<p>Polyclonal B cell activation can lead to the stimulation of autoreactive lymphocytes, promoting the development of autoimmune diseases.</p> Signup and view all the answers

What are the implications of defective regulatory T-cell development in autoimmune diseases?

<p>Defective regulatory T-cell development can fail to maintain peripheral and central tolerance, increasing susceptibility to autoimmunity.</p> Signup and view all the answers

How does the release of sequestered self antigens contribute to autoimmune processes?

<p>Release of sequestered self antigens exposes hidden epitopes, often due to tissue trauma or inflammation, triggering immune responses.</p> Signup and view all the answers

What is the association between HLA alleles and autoimmune diseases?

<p>Certain HLA alleles, like HLA-B27, are strongly associated with increased incidences of autoimmune diseases such as ankylosing spondylitis.</p> Signup and view all the answers

What are the mechanisms through which infections can precipitate autoimmune diseases?

<p>Infections may cause autoimmune diseases by modifying self-antigens, leading to cross-reaction, and inducing necrosis and inflammation.</p> Signup and view all the answers

How does the familial incidence of autoimmune diseases emphasize the role of genetic factors?

<p>A familial increase in certain autoimmune diseases, such as systemic lupus erythematosus (SLE), indicates a genetic predisposition to autoimmunity.</p> Signup and view all the answers

What happens when there is a failure of T cell-mediated suppression, such as in AIDS?

<p>Failure of T cell-mediated suppression can lead to increased immune activation and the potential development of autoimmune conditions.</p> Signup and view all the answers

In what way does the presence of complex, multigenic patterns affect the understanding of autoimmune diseases?

<p>The complex, multigenic patterns suggest that autoimmune diseases cannot be attributed to single gene mutations but rather interactively involve multiple genetic defects.</p> Signup and view all the answers

What is immunologic tolerance and how does it relate to autoimmunity?

<p>Immunologic tolerance is the inability of the immune system to respond to a specific antigen, crucial for preventing autoimmune reactions against self-antigens.</p> Signup and view all the answers

Distinguish between central tolerance and peripheral tolerance.

<p>Central tolerance involves clonal deletion of autoreactive lymphocytes in the thymus or bone marrow, while peripheral tolerance addresses autoreactive cells that escape central tolerance through mechanisms like anergy and suppression by regulatory T cells.</p> Signup and view all the answers

What role do regulatory T cells play in maintaining peripheral tolerance?

<p>Regulatory T cells inhibit lymphocyte activation and effector mechanisms through the secretion of cytokines like IL-10, contributing to peripheral tolerance.</p> Signup and view all the answers

Explain how antigen sequestration contributes to self-tolerance.

<p>Antigen sequestration involves certain tissues hiding their antigens behind blood-tissue barriers, preventing autoreactive lymphocytes from interacting with them.</p> Signup and view all the answers

Identify the factors that contribute to the failure of self-tolerance in autoimmune diseases.

<p>The failure of self-tolerance in autoimmune diseases can result from inherited susceptibility genes and environmental triggers such as infections.</p> Signup and view all the answers

Describe the process of clonal deletion in central tolerance.

<p>Clonal deletion involves the apoptosis of autoreactive T and B lymphocytes during their development in the thymus or bone marrow.</p> Signup and view all the answers

What is anergy in the context of peripheral tolerance?

<p>Anergy refers to the irreversible functional inactivation of autoreactive cells that escape central tolerance, preventing them from mounting an immune response.</p> Signup and view all the answers

How do mutations in apoptosis genes relate to autoimmune lymphoproliferative disorders?

<p>Mutations in apoptosis genes can lead to inadequate deletion of autoreactive lymphocytes, resulting in autoimmune lymphoproliferative disorders.</p> Signup and view all the answers

Illustrate how environmental factors may trigger autoimmune responses in genetically susceptible individuals.

<p>Environmental factors, like infections, can interact with genetic susceptibility genes, leading to the breakdown of self-tolerance and subsequent autoimmune reactions.</p> Signup and view all the answers

What clinical conditions can arise as a consequence of disturbances in immunologic tolerance?

<p>Disturbances in immunologic tolerance can lead to various autoimmune diseases, including rheumatoid arthritis, lupus, and type 1 diabetes.</p> Signup and view all the answers

Study Notes

Tolerance and Autoimmune Disorders

  • Tolerance is the immune system's inability to mount a response against self-antigens.
  • Self-tolerance is crucial for avoiding immune responses against our own cells and tissues.
  • Central tolerance involves the elimination of autoreactive T and B lymphocytes in the thymus or bone marrow.
  • Peripheral tolerance involves mechanisms that remove or inactivate autoreactive cells that escape central tolerance, including anergy, suppression by regulatory T cells, and deletion via apoptosis.
  • Autoimmune diseases occur when self-tolerance breaks down, allowing immune responses against self-antigens.

Mechanisms of Autoimmunity

  • Failure of self-tolerance: Inheritance of genes contributing to a breakdown of self-tolerance or the regulation of immune responses.
  • Breakdown of T cell anergy: Up-regulation of costimulatory molecules on antigen-presenting cells (APCs), leading to the activation of T cells specific to self-antigens.
  • Failure of T cell-mediated suppression: Occurs in conditions like AIDS, affecting the regulation of T cell responses.
  • Molecular mimicry: Similar amino acid sequences between a pathogen and a self-antigen, leading to cross-reactivity, where the immune response is directed at the self-antigen.

Role of Susceptibility Genes

  • HLA alleles are associated with autoimmunity, such as HLA-B27 and ankylosing spondylitis.
  • Genetic defects in apoptotic pathways can influence tolerance.
  • Defective regulatory T-cell development contributes to autoimmune diseases.

Role of Infection

  • Viral infections can play a role in triggering autoimmune diseases by modifying self-antigens.
  • Cross-reactivity: Pathogens may share epitopes (surface features) with self-antigens.
  • Microbial agents causing necrosis and inflammation upregulate co-stimulatory molecules, exposing hidden antigens, and causing polyclonal activation of lymphocytes.

Classification of Autoimmune Diseases

  • Organ-specific autoimmune diseases target specific organs (e.g., Grave's disease of the thyroid gland, Type 1 diabetes mellitus, myasthenia gravis).
  • Systemic autoimmune diseases affect multiple organs (e.g., Systemic Lupus Erythematosus, rheumatoid arthritis, inflammatory bowel diseases).

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Tolerance, Autoimmune Disorders PDF

Description

Explore the concepts of tolerance and autoimmune disorders in this quiz. Understand how self-tolerance is crucial for preventing immune responses against our own cells and tissues. Learn about central and peripheral tolerance, and the mechanisms that lead to autoimmune diseases.

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