Introduction to Autoimmunity and Immune Response

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Questions and Answers

What is the primary cause of Guillain-Barré syndrome as described in the passage?

  • The inability to fight off common bacteria due to a compromised immune system.
  • An autoimmune response triggered by a bacterial infection. (correct)
  • A genetic predisposition leading to a weakened immune system.
  • A viral infection, causing inflammation of the nervous system.

What role do predisposing genes and MHC haplotypes play in the development of Guillain-Barré syndrome?

  • They directly cause the autoimmune reaction to myelin.
  • They directly influence the severity of the syndrome after a bacterial infection.
  • They directly inhibit the immune system's ability to fight off bacterial infections.
  • They create a susceptibility to developing the syndrome after a bacterial infection. (correct)

How does the immune response in Guillain-Barré syndrome ultimately resolve itself?

  • The bacteria that triggered the syndrome is eliminated, leading to a decrease in the immune response. (correct)
  • The body's immune response eventually weakens and the symptoms subside.
  • The immune system learns to recognize myelin as harmless and stops attacking it.
  • The virus that causes the syndrome eventually weakens and is eliminated by the body.

What is the significance of developing immune memory, as mentioned with regards to vaccines?

<p>It allows the body to mount a quicker and more effective immune response to a specific pathogen upon a second exposure. (A)</p> Signup and view all the answers

Why is it important for T lymphocytes to receive Signal 2 (CD8) during T cell activation?

<p>Signal 2 ensures the T cell produces memory cells for future encounters with the pathogen. (D)</p> Signup and view all the answers

What happens to T lymphocytes that fail to receive Signal 2 (CD8) during T cell activation?

<p>They become anergic and suppress the immune response to all antigens. (D)</p> Signup and view all the answers

What is the function of regulatory T cells, as described in the passage?

<p>To suppress the immune response and prevent immune system overactivation. (B)</p> Signup and view all the answers

Why did a significant number of individuals die during the COVID-19 pandemic?

<p>The immune response to the virus was delayed, allowing the virus to replicate and cause severe complications. (D)</p> Signup and view all the answers

What is the primary goal of a bone marrow transplant in the treatment of autoimmune diseases?

<p>To introduce a new immune system that is not reactive to the body's own tissues. (B)</p> Signup and view all the answers

What is the role of cyclophosphamide in the bone marrow transplant procedure?

<p>To mobilize stem cells from the blood. (C)</p> Signup and view all the answers

What type of cells are targeted for collection during a bone marrow transplant?

<p>CD34 positive cells. (D)</p> Signup and view all the answers

What is the purpose of the conditioning step in a bone marrow transplant?

<p>To eliminate the existing bone marrow cells. (B)</p> Signup and view all the answers

What is the significance of myeloablative treatments in bone marrow transplantation for autoimmune diseases?

<p>They are the most effective treatments for autoimmune diseases. (B)</p> Signup and view all the answers

Why is collecting stem cells from peripheral blood preferred over bone marrow biopsy in modern bone marrow transplant procedures?

<p>Peripheral blood stem cell collection is less invasive. (A)</p> Signup and view all the answers

What is the main principle behind the use of bone marrow transplants in the treatment of autoimmune diseases?

<p>Introducing a new immune system that is not reactive to the body's own tissues. (A)</p> Signup and view all the answers

Which of the following statements accurately describes the mechanism of bone marrow transplantation in autoimmune diseases?

<p>The transplanted stem cells generate a new immune system that is tolerant to the body's own tissues. (C)</p> Signup and view all the answers

What type of cells are responsible for initiating an immune response?

<p>Antigen presenting cells (APCs) (D)</p> Signup and view all the answers

What is the main environmental factor that has contributed to the rise of autoimmune diseases post World War II?

<p>Decreased exposure to environmental antigens (D)</p> Signup and view all the answers

How does the immune system differentiate between self and non-self antigens?

<p>By the presence of MHC molecules on the surface of cells (D)</p> Signup and view all the answers

Which type of MHC molecule presents proteins from inside the cell?

<p>MHC class 1 (C)</p> Signup and view all the answers

What is the role of NK cells in the immune system?

<p>To kill cells that lack MHC molecules (C)</p> Signup and view all the answers

Which of the following is NOT a characteristic of autoimmune diseases?

<p>They are always treatable with antibiotics (A)</p> Signup and view all the answers

According to the passage, why has the incidence of autoimmune diseases increased since the second World War?

<p>The decrease in exposure to environmental antigens (D)</p> Signup and view all the answers

The passage mentions a link between autoimmune diseases and the decline of parasites. Which of the following best describes the relationship?

<p>The absence of parasites has altered the immune system's normal function, leading to autoimmune problems (A)</p> Signup and view all the answers

What is the main reason why bone marrow transplantation is not used for every patient with an autoimmune disease?

<p>The procedure is associated with significant risks. (D)</p> Signup and view all the answers

What evidence suggests that MS is an immune-mediated disease?

<p>The success of bone marrow transplantation in resolving the disease. (D)</p> Signup and view all the answers

What happens to the patient's immune system during the recovery phase after bone marrow transplantation?

<p>The immune system is re-established with new memory cells. (D)</p> Signup and view all the answers

What is a significant risk associated with bone marrow transplantation during the recovery phase?

<p>The risk of developing infections. (D)</p> Signup and view all the answers

Why is it considered unethical to propose bone marrow transplantation for every patient with an autoimmune disease?

<p>The procedure carries significant risks, and not all patients are suitable candidates. (A)</p> Signup and view all the answers

What does the author mean by saying that the transplant process "demonstrates that substituting the existing immune system with a new one can lead to the resolution of the disease"?

<p>The immune system plays a key role in the development of MS. (D)</p> Signup and view all the answers

Which of the following statements is TRUE about bone marrow transplantation for MS?

<p>The procedure can be considered for patients who are not responding to other treatments. (A)</p> Signup and view all the answers

What conclusion can be drawn from the success of bone marrow transplantation in resolving MS?

<p>MS is an immune-mediated disease. (B)</p> Signup and view all the answers

Why are the T lymphocytes that have a very high affinity for antigens within the thymus eliminated?

<p>They potentially recognize self-antigens and could lead to autoimmune diseases. (C)</p> Signup and view all the answers

What happens to T lymphocytes with very low affinity for antigens within the thymus?

<p>They are eliminated because they may not be functional. (B)</p> Signup and view all the answers

What is the main function of T-regulatory cells in the immune system?

<p>To suppress immune responses and prevent autoimmunity. (A)</p> Signup and view all the answers

What condition results from a genetic defect in FOXP3?

<p>Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked syndrome (IPEX) (D)</p> Signup and view all the answers

What is the effect of a severe impairment or deletion of the FOXP3 protein?

<p>Increased susceptibility to autoimmune diseases. (C)</p> Signup and view all the answers

Which of the following is NOT a consequence of a dysfunctional T-regulatory cell?

<p>Enhanced immune response to viral infections. (D)</p> Signup and view all the answers

What type of cell, besides T-regulatory cells, has been identified as playing a role in immune regulation?

<p>Suppressive myeloid cells (B)</p> Signup and view all the answers

Which statement accurately reflects the importance of T-regulatory cells in the immune system?

<p>They are crucial for maintaining immune balance and preventing autoimmunity. (D)</p> Signup and view all the answers

What is the primary consequence of the absence of functioning T-regulatory cells?

<p>Development of autoimmune diseases. (A), Increased susceptibility to infections like polio. (D)</p> Signup and view all the answers

What is the key characteristic that distinguishes bystander activation in autoimmune diseases?

<p>The immune response is triggered by a danger signal unrelated to the autoantigen. (D)</p> Signup and view all the answers

Which of the following conditions IS NOT an example of an autoimmune disease?

<p>Paraneoplastic syndrome (C)</p> Signup and view all the answers

What is the dilemma faced by healthcare providers in cases of paraneoplastic syndromes?

<p>Balancing the immune system's power to fight the tumor against its potential to cause autoimmune reactions. (B)</p> Signup and view all the answers

Flashcards

Autoimmune Disease Resolution

The improvement or disappearance of symptoms in autoimmune diseases following treatment.

Bone Marrow Transplant Risks

The potential dangers including infections and complications from undergoing a bone marrow transplant.

Procedure-related Mortality

The risk of death directly associated with bone marrow transplantation procedures, estimated around 1-2%.

Ethical Patient Selection

Choosing patients for transplantation based on severe conditions and lack of responses to other treatments.

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Post-Transplant Vaccinations

The requirement for patients to receive vaccinations again after their immune system is re-established post-transplant.

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Immune-mediated Mechanism

The concept that diseases like MS are caused by the immune system's own activity rather than other mechanisms.

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Memory Cell Elimination

The process during a transplant where all immune memory cells are destroyed, requiring a complete reset of the immune system.

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MS Inflammation Cause

The inflammation in Multiple Sclerosis is a direct consequence of immune activity, not due to hidden viruses or other mechanisms.

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T lymphocyte affinity selection

Process where T lymphocytes are eliminated based on their affinity for antigens in the thymus.

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Autoreactive T cells

T cells that may react against the body's own tissues, causing autoimmune issues.

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Thymus function

The thymus educates T lymphocytes by eliminating those that are too strong or too weak.

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FOXP3 gene

Gene critical for the development of regulatory T cells; defects can lead to autoimmune diseases.

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IPEX syndrome

Condition caused by FOXP3 mutation, leading to immune dysregulation and autoimmune disorders.

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T-regulatory cells

A subtype of T cells that help maintain immune balance and prevent autoimmunity.

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Peripheral tolerance

Mechanism that prevents the immune system from attacking the body's own tissues.

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Suppressive myeloid cells

Recent discoveries highlight these cells as contributors to immune regulation alongside T-reg cells.

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Guillain-Barré syndrome

An autoimmune disease causing neurological damage due to molecular mimicry.

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Molecular mimicry

The phenomenon where immune response to an infection damages body tissues due to similarity in structures.

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Campylobacter jejuni

A bacterium causing gut infections that can trigger autoimmune reactions in genetically predisposed individuals.

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MHC molecules

Major Histocompatibility Complex molecules present antigens and activate T lymphocytes.

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Signal II in T lymphocytes

The secondary signal required for T cell activation, often via CD8 receptors.

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Effector T lymphocytes

T cells that actively respond to antigens and help in immune reactions.

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Self-limiting mechanisms

The body's natural capability to halt an immune response after the threat is eliminated.

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Autoimmune disease mechanism

An outside-in mechanism where tissue reactivity generates in the periphery and enters the brain.

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Inside-out mechanism

A scenario where damage originates internally, leading to inflammatory responses.

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Oligodendrocytes

Cells that produce myelin in the central nervous system, which can die and lead to inflammatory responses.

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Bone marrow transplant

A medical procedure to transfer stem cells to replace the damaged immune system.

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CD34 positive cells

Stem cells capable of generating various blood cells, crucial for bone marrow transplants.

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Conditioning regimen

The use of chemotherapy to eliminate existing bone marrow cells before transplantation.

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Myeloablative treatment

An aggressive approach aiming to completely destroy the existing immune system for transplantation.

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Stem cell repopulation

The process where infused stem cells regenerate a new immune system after transplantation.

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Autoimmune diseases

Conditions where the immune system mistakenly attacks the body.

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Increase in autoimmunity

Rising rates of autoimmune diseases since WWII.

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Antigenic challenge

Exposure to foreign substances that trigger immune responses.

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MHC Class 1

MHC molecule present on almost all body cells.

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MHC Class 2

MHC molecule found on antigen presenting cells (APCs).

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Antigen Presenting Cells (APCs)

Cells that process and present antigens for T-cell activation.

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Natural Killer (NK) cells

Immune cells that kill infected or abnormal cells without MHC needed.

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Bystander activation

An immune response triggered by a danger signal that targets autoantigens unnecessarily.

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Autoimmunity

A condition where the immune system mistakenly attacks the body’s own cells.

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Paraneoplastic syndromes

Disorders arising from immune responses to tumors that can cause autoimmune reactions.

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Lupus

An autoimmune disease causing inflammation and damage to various body parts.

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Crohn's disease

A type of inflammatory bowel disease involving chronic inflammation in the digestive tract.

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Study Notes

Introduction to Autoimmunity

  • Autoimmune diseases have increased since WWII
  • Reduced exposure to antigens in modern lifestyles
  • Immune system now encounters unusual antigens more frequently
  • Example - lack of parasitic infections
  • Immune response (image) shows dynamic interaction with pathogens or self-antigens, including antigen-presenting cells (APCs)

MHC Molecules and Immune Response Initiation

  • Two types of MHC molecules: MHC class I and MHC class II
  • MHC molecules are surface molecules
  • MHC class I molecules present intracellular proteins on cell surfaces
  • MHC class II molecules present extracellular proteins on the surface of antigen-presenting cells (APCs)
  • NK cells bridge innate and adaptive immunity, killing cells lacking or mismatched MHC molecules
  • APCs present antigens to T cells

B and T Cell Receptors and Diverse Responses

  • B and T cells have diverse receptors due to unique genomic recombination process
  • T cells proliferate and differentiate into effector T cells after activation by antigen presenting cells (APCs) that recognize matching protein
  • Adaptive immune response takes around 15-60 minutes (signal 1) and 40-60 mins (signal 2)
  • This leads to clonal expansion and maturation to effector function

Mechanisms of Diverse Immune Responses

  • Bystander activation, where a danger signal activates an unrelated immune response.
  • Molecular mimicry, where the body's immune system responds to a pathogen by targeting similar molecules in the body.

Autoimmune Diseases

  • Multiple mechanisms can contribute to autoimmune diseases.
  • Chronic inflammation and tissue damage can result.
  • Genetic predisposition and environmental factors can contribute.

Role of the Thymus

  • The thymus is an organ where T cells mature and are selected
  • T cells that recognize self-antigens with high affinity are deleted
  • This peripheral tolerance helps prevent autoimmunity
  • Failure of selection mechanisms can lead to autoimmune responses

Mechanisms of Autoimmune Diseases

  • Autoimmune diseases can manifest as a variety of conditions, some of which simultaneously include neurological, arthritic, and gut diseases
  • These diseases are characterized by complex and multiple mechanisms (e.g., bystander activation, molecular mimicry).

Paraneoplastic Syndromes

  • Associated with tumors
  • Immune responses are complex and potentially detrimental (e.g., damaging normal cells along with tumor cells).
  • Include several types (e.g., affecting central nervous system or muscle tissues).

Development of Autoimmune Diseases

  • Genetic risk factors can predispose individuals to autoimmune diseases.
  • Environmental factors can influence disease development.
  • A combination of genetic and environmental factors is often seen to affect onset of autoimmune disease

Myelin and its Importance in MS

  • Normal myelin sheath = high conduction velocity (100 m/s)
  • Loss of myelin sheath slows down nerve pulse conduction (1 m/s).
  • This is evidenced by MRI scans.

Autoimmune Diseases and Treatment

  • Treatment options are limited to immunosuppressants, though certain types of cell replacement strategies (e.g., stem cell transplant) for autoimmune diseases.

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