Autoimmune Diseases Overview

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Questions and Answers

What is the primary consequence of autoantibodies and autoreactive T cells in pernicious anemia?

Overproduction of intrinsic factor

Direct damage to gastric parietal cells (correct)

Enhanced immune response against Helicobacter pylori

Increased production of gastric acid

In Hashimoto thyroiditis, what role do autoantibodies play?

They inhibit the production of iodine and cause inflammation. (correct)

They prevent the activation of cytotoxic T cells.

They enhance the function of thyroid peroxidase.

They stimulate increased thyroid hormone production.

Which immune cells are primarily involved in the direct cellular damage seen in Hashimoto thyroiditis?

B cells and macrophages

Natural killer cells and dendritic cells

Cytotoxic T lymphocytes and Th1 cells (correct)

Helper T cells and neutrophils

What is a potential underlying factor linked to autoimmune reactions in pernicious anemia?

Helicobacter pylori infection Signup and view all the answers

What is the result of the damage caused by autoantibodies in Hashimoto thyroiditis?

Hypothyroidism and goiter formation Signup and view all the answers

What is the primary mechanism of cytotoxicity in Type 1 Diabetes Mellitus?

Delated type hypersensitivity Signup and view all the answers

Which type of immune response is primarily involved in Multiple Sclerosis?

Cell-mediated immunity Signup and view all the answers

What triggers the entry of self-reactive T cells into the CNS in Multiple Sclerosis?

Disruption of the blood-brain barrier Signup and view all the answers

Which autoantigen is commonly targeted in Multiple Sclerosis?

Myelin basic protein Signup and view all the answers

Which therapy is a type of S1P receptor modulator used for Multiple Sclerosis?

Fingolimod Signup and view all the answers

What role do autoantibodies play in Type 1 Diabetes Mellitus?

Activating complement or ADCC Signup and view all the answers

What is the relationship between viral infections and Type 1 Diabetes Mellitus?

Viral infections may trigger an autoimmune response Signup and view all the answers

Which of the following is NOT a component of the immune response in Multiple Sclerosis?

B cell anergy Signup and view all the answers

Which of the following describes the role of Effector TH1 cytokines in T1DM?

Stimulating local inflammation Signup and view all the answers

What type of immune response primarily contributes to the damage in the central nervous system in Multiple Sclerosis?

Cell-mediated immune response Signup and view all the answers

Which autoantibody is classified as an IgM anti-IgG antibody commonly found in rheumatoid arthritis patients?

Rheumatoid factor (RF) Signup and view all the answers

What is the primary function of TNF inhibitors in the treatment of rheumatoid arthritis?

They bind and neutralize TNF. Signup and view all the answers

Which of the following is a CTLA-4 fusion protein that inhibits T cell activation?

Abatacept (Orencia®) Signup and view all the answers

Which cytokine is directly inhibited by Anakinra (Kineret®)?

Interleukin-1 (IL-1) Signup and view all the answers

What critical change occurs during the citrullination of proteins that stimulates an immune response in rheumatoid arthritis?

The proteins undergo alteration from arginine to citrulline. Signup and view all the answers

Which type of cytokines are found to be increased in rheumatoid arthritis due to the activation of TH1 and TH17 cells?

Proinflammatory cytokines Signup and view all the answers

What is the mechanism by which autoantibodies contribute to tissue damage in rheumatoid arthritis?

They form immune complexes that deposit in tissues. Signup and view all the answers

Which treatment for rheumatoid arthritis targets and blocks the IL-6 receptor?

Tocilizumab (Actemra®) Signup and view all the answers

What is the primary effect of anti-TSHR antibodies in Graves disease?

Overstimulation of thyroid hormone production Signup and view all the answers

In Myasthenia Gravis, how do autoantibodies affect neuromuscular transmission?

They block the binding of ACh to AChR. Signup and view all the answers

What specific mechanism leads to megaloblastic anemia in pernicious anemia?

Decreased absorption of vitamin B12 Signup and view all the answers

Which of the following is a common early sign of Myasthenia Gravis?

Ptosis Signup and view all the answers

What is the role of intrinsic factor in vitamin B12 absorption?

It binds to vitamin B12 and facilitates its absorption. Signup and view all the answers

Which condition is characterized by autoantibodies acting as agonists?

Graves disease Signup and view all the answers

What is the expected effect of autoantibodies in organ-specific autoimmunities?

Suppression of normal tissue function Signup and view all the answers

What is a possible consequence of anti-AChR antibodies in Myasthenia Gravis?

Muscle weakness Signup and view all the answers

Which autoimmune disease is associated with inflammation of the orbit and periorbital tissues?

Graves disease Signup and view all the answers

What happens when intrinsic factor is blocked by autoantibodies in pernicious anemia?

Vitamin B12 absorption is decreased Signup and view all the answers

What is the primary mechanism by which Rituximab leads to B cell depletion?

It binds to and destroys B cells. Signup and view all the answers

In systemic lupus erythematosus (SLE), which type of antibodies are most commonly found?

Anti-dsDNA and anti-Sm antibodies. Signup and view all the answers

What role do anti-nuclear antibodies (ANAs) play in the pathology of SLE?

They form immune complexes with nuclear antigens. Signup and view all the answers

What consequence does the deposition of immune complexes in the vasculature have in SLE?

Activation of complement and tissue damage. Signup and view all the answers

What happens after the immune complexes are endocytosed by B cells and dendritic cells?

They trigger secretion of IFN-α. Signup and view all the answers

What are the factors contributing to the breakdown of tolerance to self-antigens in SLE?

Environmental, hormonal, and genetic factors. Signup and view all the answers

What is the result of defective clearance of apoptotic bodies in SLE?

Enhanced release of nuclear antigens. Signup and view all the answers

Which component is primarily targeted by anti-Sm antibodies in SLE?

Ribonucleoproteins. Signup and view all the answers

Study Notes

Graves Disease

Autoantibodies overstimulate the thyroid stimulating hormone receptor (TSHR)
Unregulated activation and overproduction of thyroid hormones result in hyperthyroidism
Patients may present with proptosis, inflammation of the orbit, and periorbital tissues

Myasthenia Gravis (MG)

Autoantibodies block acetylcholine (ACh) from binding to acetylcholine receptors (AChR) on the neuromuscular junction
Anti-AChR antibodies act as competitive receptor antagonists
Most frequent early sign of MG is ptosis (drooping eyelids)
Autoantibodies can cause complement-mediated destruction of the muscle fibers

Pernicious Anemia

Autoantibodies block absorption of vitamin B12
Dietary vitamin B12 is absorbed when bound to intrinsic factor (IF)
IF is secreted by gastric parietal cells
Anti-intrinsic factor antibodies block IF binding to B12 and IF-B12 binding to the IF receptor
Decreased vitamin B12 absorption leads to decreased erythropoiesis, resulting in megaloblastic anemia
Hypersegmented polymorphonuclear neutrophils (PMNs) are often seen in pernicious anemia

Autoimmune-Mediated Damage

Organ-specific autoimmunities can damage tissues in two main ways:
- Autoantibodies and/or autoreactive T cells can cause direct cellular damage
- Autoantibodies and/or autoreactive T cells can trigger inflammation and tissue damage
Cellular lysis and/or inflammatory responses result in the replacement of normal tissue with connective tissue (fibrosis)
Examples of diseases with direct cellular damage are:
- Pernicious anemia
- Hashimoto thyroiditis
- Type 1 diabetes mellitus
- Multiple sclerosis

Pernicious Anemia - Direct Cellular Damage

Autoantibodies and cytotoxic T lymphocytes (CTLs) can cause direct cellular damage to gastric parietal cells
Anti-parietal cell antibodies and autoreactive CTLs target the H+,K+-ATPase pump
This results in killing of parietal cells, reduced intrinsic factor production, and ultimately, pernicious anemia
Possible link to Helicobacter pylori infection

Hashimoto Thyroiditis - Direct Cellular Damage

Autoantibodies and autoreactive T cells cause direct cellular damage to the thyroid gland
CTLs and TH1 cells cause inflammation and damage to the thyroid, resulting in a goiter
Anti-thyroid peroxidase (TPO) and/or anti-thyroglobulin (Tg) antibodies inhibit production of iodine, activate complement, and induce antibody-dependent cellular cytotoxicity (ADCC)
Results in hypothyroidism

Type 1 Diabetes Mellitus (T1DM) - Direct Cellular Damage

Autoantibodies and autoreactive T cells cause direct cellular damage to the pancreas
Possible link to viral infections
Delayed-type hypersensitivity (DTH) response (a type of cell-mediated immunity) destroys pancreatic beta cells
Effector CTLs directly destroy beta cells
Effector TH1 cytokines stimulate local inflammation
Several autoantibodies can be found in patients with T1DM, which activate complement or induce ADCC

Multiple Sclerosis (MS) - Direct Cellular Damage

Autoantibodies and autoreactive T cells cause direct cellular damage to the central nervous system (CNS)
Infections and/or tissue damage may cause a disruption of the blood-brain barrier (BBB), leading to the release of CNS antigens
This allows self-reactive T cells to enter the CNS
Cell-mediated immune (CMI) response: T cells and macrophages infiltrate the CNS and attack myelin proteins
Humoral response: autoantibodies to myelin proteins can activate complement or induce ADCC

Systemic: Rheumatoid Arthritis (RA)

Autoreactive T and B cells are activated, leading to increased levels of TH1 and TH17 cytokines, as well as macrophage inflammatory cytokines
Autoantibodies form immune complexes that can deposit into tissues, causing tissue damage

Rheumatoid Arthritis (RA) - Common Autoantibodies

Rheumatoid Factor (RF): IgM anti-IgG antibody
- May be caused by exposure of hidden carbohydrates on IgG (cryptic epitopes)
Anti-citrullinated peptide antibodies (ACPA):
- Anti-CCP and anti-MCV antibodies target citrullinated proteins (altered self), stimulating an immune response

Immunotherapies for RA

Block the effects of proinflammatory cytokines:
- TNF inhibitors: bind and neutralize TNF
- Anakinra (Kineret®): IL-1R antagonist
- Tocilizumab (Actemra®): anti-IL-6R
- Tofacitinib (Xeljanz®): JAK1/3 inhibitor
Inhibit T cell activation: Abatacept (Orencia®): CTLA-4 fusion protein that binds B7; blocks the T cell costimulatory signal
Deplete B cells: Rituximab (Rituxan®): anti-CD20 antibody that binds to B cells, resulting in B cell destruction (depletion)

Systemic: Systemic Lupus Erythematosus (SLE)

Genetic, hormonal, and environmental factors contribute to a breakdown of tolerance to self-antigens, mainly nuclear antigens
Defective clearance of apoptotic bodies and/or the release of neutrophil extracellular traps (NETs) can lead to the release of nuclear antigens
This stimulates self-reactive T and B cells against these nuclear antigens, resulting in the generation of antinuclear antibodies (ANAs)

Systemic: Systemic Lupus Erythematosus (SLE) - Common ANAs

Most common ANAs are anti-dsDNA and anti-Sm antibodies
- Anti-dsDNA target double-stranded DNA
- Anti-Sm target the Sm ribonucleoprotein (an antigen found in the nucleus)
ANAs form immune complexes that bind to nuclear antigens
These immune complexes are endocytosed by B cells and dendritic cells
Plasmacytoid dendritic cells (pDCs) secrete IFN-α, which triggers continued ANA production

Systemic: Systemic Lupus Erythematosus (SLE) - Consequences of Immune Complexes

Immune complexes deposit in the vasculature/joints, activating complement and leading to tissue damage
The result is inflammation, tissue damage, and various SLE symptoms

Immunotherapies For MS

S1P receptor modulators:
- Fingolimod (Gilenya®) and Ozanimod (Zeposia®) are S1P receptor agonists
- They downregulate S1PR1, retaining lymphocytes within the lymphatic tissues, reducing inflammation in the CNS
- There are other S1P receptor modulators available on the market for MS treatment

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Description

This quiz covers key autoimmune diseases, including Graves' disease, Myasthenia Gravis, and Pernicious Anemia. It explores their mechanisms, symptoms, and the role of autoantibodies in these conditions. Gain insights into the clinical presentations and implications of these autoimmune disorders.