Tolerance and Autoimmune Disorders
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Questions and Answers

What best describes central tolerance in the immune system?

  • The suppression of autoreactive responses by cytokines from regulatory T cells.
  • Deactivation of autoreactive cells through antigen sequestration.
  • Functional inactivation of autoreactive lymphocytes outside of primary lymphoid organs.
  • Clonal deletion of autoreactive T and B lymphocytes in the thymus or bone marrow. (correct)

Which mechanism is NOT a primary function of peripheral tolerance?

  • Apoptosis initiated by pathogenic infections. (correct)
  • Cytokine secretion leading to suppression of lymphocyte activation.
  • Sequestration of antigens in specific tissues.
  • Anergy through irreversible functional inactivation.

What causes the breakdown of self-tolerance leading to autoimmune diseases?

  • Exclusively genetic susceptibility factors.
  • Environmental triggers in conjunction with genetic factors. (correct)
  • Increased production of regulatory T cells.
  • Isolation of immune cells from self-antigens.

Which of the following correctly identifies a consequence of traumatic injury in relation to autoimmune responses?

<p>It exposes sequestered antigens, potentially triggering an autoimmune reaction. (D)</p> Signup and view all the answers

Which statement is true concerning autoimmune lymphoproliferative disorders?

<p>They are usually caused by failure of apoptosis in autoreactive lymphocytes. (B)</p> Signup and view all the answers

What role does antigen sequestration play in maintaining self-tolerance?

<p>It hides self-antigens from immune surveillance behind barriers. (B)</p> Signup and view all the answers

Which factor is NOT typically involved in the mechanisms of autoimmunity?

<p>Direct damage to immune system by external forces. (B)</p> Signup and view all the answers

Which statement about autoimmune diseases is NOT accurate?

<p>The symptoms of autoimmune diseases are always distinct and easily classified. (C)</p> Signup and view all the answers

Which of the following is classified as an organ-specific autoimmune disease?

<p>Grave's disease (D)</p> Signup and view all the answers

What common factor can influence the manifestation of autoimmune diseases?

<p>Age, hormones, and environmental factors (A)</p> Signup and view all the answers

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

<p>Upregulation of costimulatory molecules on APCs (A)</p> Signup and view all the answers

Which of the following phenomena is best exemplified by rheumatic heart disease?

<p>Molecular mimicry (A)</p> Signup and view all the answers

What is the most significant association of HLA alleles with autoimmune disease?

<p>Ankylosing spondylitis with HLA-B27 (C)</p> Signup and view all the answers

What mechanism involves the alteration of self antigens by microbial agents leading to autoimmune diseases?

<p>Modification of self antigens (B)</p> Signup and view all the answers

What role does tissue trauma play in the development of autoimmune diseases?

<p>It exposes hidden epitopes through inflammatory destruction (D)</p> Signup and view all the answers

Which of the following statements is true regarding susceptibility genes in autoimmune diseases?

<p>They typically show complex, multigenic patterns of susceptibility (B)</p> Signup and view all the answers

Which microorganism is known to cause polyclonal activation of B cells leading potentially to autoreactivity?

<p>Epstein-Barr virus (EBV) (B)</p> Signup and view all the answers

How does failure of T cell mediated suppression contribute to autoimmune diseases?

<p>It allows activated T cells to respond to self-antigens (D)</p> Signup and view all the answers

Which of the following methods can lead to autoimmune reactions through molecular mimicry?

<p>Cross-reactivity with similar amino acid sequences (C)</p> Signup and view all the answers

What can trigger the release of sequestered self antigens, potentially leading to autoimmune responses?

<p>Tissue trauma or inflammatory destruction (B)</p> Signup and view all the answers

Flashcards

Autoimmune Disease

A disease caused by the immune system attacking the body's own tissues, disrupting normal organ function.

Autoimmune hemolytic anemia

Type II hypersensitivity reaction, where antibodies target self-antigens on cell surfaces, leading to cell destruction.

Systemic Lupus Erythematosus (SLE)

Type III hypersensitivity reaction, where immune complexes accumulate in tissues, triggering inflammation and damage.

Organ-Specific Autoimmune Disease

A category of autoimmune diseases that affect specific organs or tissues, like the thyroid, pancreas, or muscles.

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Systemic Autoimmune Disease

Autoimmune diseases affecting multiple organ systems simultaneously, with widespread inflammation and damage.

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Immunological Tolerance

The state where the immune system doesn't attack the body's own cells and tissues.

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Central Tolerance

A type of tolerance that shuts down self-reactive immune cells during their development in the bone marrow or thymus.

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Peripheral Tolerance

A type of tolerance that removes or deactivates self-reactive immune cells after they leave the bone marrow or thymus.

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Anergy

A mechanism where self-reactive immune cells are permanently inactivated after they've left the bone marrow or thymus.

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Suppression by Regulatory T Cells

Regulatory T cells (Tregs) suppress other immune cells, preventing them from attacking the body's own tissues.

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Autoreactive Lymphocyte Deletion

A process where self-reactive immune cells undergo programmed cell death to eliminate them.

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Antigen Sequestration

A mechanism where the immune system can't access certain tissues like the brain, eye, and testis, blocking the occurrence of autoimmune reactions.

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T cell anergy breakdown

Breakdown of T cell anergy occurs when the expression of costimulatory molecules on antigen-presenting cells (APCs) is upregulated. This leads to the activation of T cells specific for self-antigens, overcoming their state of unresponsiveness.

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Failure of T cell suppression

A situation where T cell-mediated suppression is deficient, like in HIV/AIDS, leading to uncontrolled immune responses and potential autoimmunity.

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Molecular mimicry

When a microbe shares amino acid sequences with a self-antigen, the immune system may attack both, leading to tissue damage and autoimmune reactions.

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Polyclonal B cell activation

A mechanism that can trigger autoimmunity; certain microbes or their products can activate many different B cells, some of which may be autoreactive.

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Exposure of hidden epitopes

Trauma or inflammation can expose hidden self-antigens, triggering an autoimmune response. For example, lens proteins in the eye or sperm cells.

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Familial increase in autoimmune disease

Increased incidence of autoimmune diseases within families suggests a genetic component. For example, Systemic Lupus Erythematosus (SLE).

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HLA allele association with autoimmunity

Certain HLA alleles (human leukocyte antigen) are strongly associated with autoimmune diseases. For example, ankylosing spondylitis and HLA-B27.

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Defective apoptotic pathways

Defects in apoptotic pathways can disrupt the normal process of eliminating self-reactive immune cells, leading to an increased risk of autoimmunity.

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Defective regulatory T cell development

If regulatory T cells (T regs), responsible for suppressing the immune system, are deficient, it can lead to uncontrolled immune responses and autoimmunity.

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Multigenic pattern of susceptibility

Many autoimmune diseases are influenced by multiple genes, making it difficult to isolate a single gene responsible for the disease.

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Role of infection in autoimmunity

Viral infections, particularly, can contribute to autoimmune diseases through various mechanisms, including modifying self-antigens, molecular mimicry, and inducing inflammation.

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Study Notes

Tolerance and Autoimmune Disorders

  • Tolerance is the inability of the immune system to respond to self-antigens.
  • Self-tolerance prevents the immune system from attacking the body's own cells and tissues.
  • Central tolerance involves clonal deletion of autoreactive T and B lymphocytes in the thymus or bone marrow.
  • Peripheral tolerance removes or deactivates autoreactive cells that escape central tolerance.
  • Anergy, suppression by regulatory T cells, and deletion by apoptosis are mechanisms of peripheral tolerance.
  • Autoimmune diseases occur when self-tolerance fails, allowing the immune system to attack self-antigens.
  • Mechanisms of autoimmunity include failure of self-tolerance, genetic factors, and infectious factors.
  • Examples of autoimmune diseases include type I diabetes mellitus, rheumatoid arthritis, systemic lupus erythematosus, and autoimmune thyroid disease.
  • Genetic defects in apoptotic pathways can lead to immune dysregulation and autoimmune diseases.

Mechanisms of Autoimmunity

  • Failure of self-tolerance: Breakdown of T cell anergy, failure of T cell suppression, molecular mimicry.
  • Genetic factors: Inheritance of susceptibility genes.
  • Infectious factors: Modification of self-antigens, cross-reaction with microbial epitopes, resulting inflammation and immune activation.
  • Molecular mimicry: When a microbial antigen resembles a self-antigen, the immune response may attack both.
  • Release of sequestered self-antigens and exposure of hidden epitopes through tissue trauma or inflammatory destruction can trigger an immune response.

Types of Autoimmune Diseases

  • Organ-specific autoimmune diseases affect a specific organ or tissue.
    • Examples include autoimmune thyroid disease, type 1 diabetes mellitus, and myasthenia gravis.
  • Systemic autoimmune diseases affect multiple organs and systems.
    • Examples include systemic lupus erythematosus, rheumatoid arthritis, and inflammatory bowel diseases.

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Tolerance, Autoimmune Disorders PDF

Description

This quiz explores the concepts of tolerance and autoimmune disorders, focusing on how the immune system distinguishes between self and non-self. It covers mechanisms of central and peripheral tolerance and the failure of self-tolerance leading to various autoimmune diseases. Test your understanding of this critical aspect of immunology.

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