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What is the definition of autoimmunity?
A misdirected immune response that occurs when the immune system attacks the body itself.
What is the mechanism for preventing autoimmunity?
Molecular mimicry involves a foreign antigen cross-reacting with self-antigens in an autoimmune disease.
True
Autoimmune conditions are classified similarly to hypersensitivity reactions, except there is no ____ hypersensitivity.
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Match the following autoimmune conditions with their corresponding immune response type:
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What is tolerance in the context of autoimmunity?
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What is the definition of autoimmunity?
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______ initiates an immune response that can lead to autoimmune disease.
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Autoimmune conditions are classified similarly to hypersensitivity reactions.
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Match the type of hypersensitivity reaction with the autoimmune condition:
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What is the most common ocular manifestation in patients with Rheumatoid Arthritis (RA)?
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What is the primary effect of Graves' disease on the eyes?
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Which of the following is a common ocular manifestation of Systemic Lupus Erythematosus (SLE)?
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What is the approximate percentage of patients with Rheumatoid Arthritis (RA) who will have ocular manifestations?
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Which demographic is more commonly affected by Graves' disease?
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What is the type of hypersensitivity reaction involved in Rheumatoid Arthritis (RA)?
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Which of the following is a complication of Graves' disease?
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What is the primary ocular manifestation of Sjögren's syndrome?
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What is the percentage of scleritis cases caused by Rheumatoid Arthritis (RA)?
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What is the key difference in symptoms between scleritis and episcleritis?
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What is the characteristic of blood vessels in scleritis?
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What is the primary cause of elevated blood glucose levels in Diabetes Mellitus (Type 1)?
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What is the primary ocular complication of Diabetes Mellitus (Type 1)?
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What is the primary characteristic of Sjögren's Syndrome?
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What is the primary mechanism for preventing complications of Diabetes Mellitus (Type 1)?
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Which autoimmune condition is associated with Graves' Disease?
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What is the primary mechanism of antibody-mediated (Type II) hypersensitivity reaction in autoimmune haemolytic anaemia?
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In systemic lupus erythematosus (SLE), what is the primary mechanism of immune complex-mediated (Type III) hypersensitivity reaction?
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What is the primary mechanism of cell-mediated (Type IV) hypersensitivity reaction in rheumatoid arthritis?
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What is the characteristic feature of Mooren's ulcer?
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What is the possible etiology of Mooren's ulcer?
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In type I diabetes mellitus, what is the primary mechanism of cell-mediated (Type IV) hypersensitivity reaction?
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What is the primary mechanism of immune-complex mediated (Type III) hypersensitivity reaction in ocular autoimmune diseases?
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What is the common feature of autoimmune conditions classified under hypersensitivity reactions?
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Which of the following mechanisms is responsible for deleting self-reactive lymphocytes in the early stages of lymphocyte development?
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What is the role of T-regulatory cells (Tregs) in the immune system?
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Which of the following is NOT a factor that contributes to abnormal regulation of the immune response?
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What is the primary consequence of molecular mimicry?
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Which of the following autoimmune conditions is NOT characterized by ocular manifestations?
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What is the primary role of the immune system in autoimmune diseases?
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Which of the following autoimmune conditions is characterized by dry eye?
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What is the primary characteristic of hypersensitivity reactions in autoimmune diseases?
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What is a possible association with sympathetic ophthalmia?
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What is the typical time frame for the presentation of sympathetic ophthalmia?
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What is a characteristic finding in keratoconjunctivitis sicca?
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What is the primary mechanism of sympathetic ophthalmia?
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What type of injury is commonly associated with sympathetic ophthalmia?
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What is a possible complication of sympathetic ophthalmia?
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What is a symptom of keratoconjunctivitis sicca?
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What is a predisposing factor for sympathetic ophthalmia?
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Study Notes
Autoimmunity
- Autoimmunity is a misdirected immune response that occurs when the immune system attacks the body itself.
- It is a hypersensitivity reaction triggered by self-antigens.
- Molecular mimicry is a mechanism that can lead to autoimmunity, where a foreign antigen initiates an immune response, and a T- or B-cell component cross-recognizes self-antigens, leading to an autoimmune disease.
Tolerance
- The body has mechanisms to remove self-reactive T- and B-cells to prevent autoimmunity.
- Central tolerance is the mechanism that deletes self-reacting lymphocytes in the early stages of lymphocyte development (in thymus or bone marrow).
- Peripheral tolerance is a "safety net" that removes self-reactive lymphocytes that have escaped central tolerance, induced in mature lymphocytes, and involves T-regulatory cells (Tregs) that suppress autoreactions.
Classification of Autoimmune Conditions
- Autoimmune conditions are classified similarly to hypersensitivity reactions, with the exception of type I hypersensitivity.
- There are three types of autoimmune conditions:
- Antibody-mediated (Type II) hypersensitivity reactions
- Immune-complex mediated (Type III) hypersensitivity reactions
- Cell-mediated (Type IV) hypersensitivity reactions
Antibody-Mediated (Type II) Hypersensitivity Reactions
- Antibody-mediated reactions occur when an antibody reacts to self-antigens, binds to tissue/cells, and results in opsonisation and complement activation.
- Example: autoimmune haemolytic anaemia.
Immune-Complex Mediated (Type III) Hypersensitivity Reactions
- Immune-complex mediated reactions occur when immune complexes are not cleared rapidly, leading to inflammation and tissue damage.
- Example: systemic lupus erythematosus (SLE).
Cell-Mediated (Type IV) Hypersensitivity Reactions
- Cell-mediated reactions occur when autoimmune T-cell responses lead to inflammation and tissue damage.
- Examples: rheumatoid arthritis, type I diabetes mellitus.
Ocular Autoimmune Diseases
- Mooren's ulcer: a rare disorder characterized by a painful, relentless, chronic ulcerative keratitis.
- Sympathetic ophthalmia: a bilateral granulomatous uveitis that occurs after a penetrating injury to one eye, potentially blinding.
Systemic Autoimmune Diseases
- Keratoconjunctivitis sicca: a dry eye syndrome characterized by dryness, corneal examination may reveal punctate erosive keratopathy or filaments.
- Scleritis: inflammation of the sclera, characterized by pain, tenderness, and decreased vision.
- Rheumatoid arthritis: a chronic inflammatory disorder that affects the joints, skin, eyes, lungs, heart, and blood vessels.
- Sjögren's syndrome: an autoimmune condition characterized by dry eyes and a dry mouth, affecting the mucous membranes and moisture-secreting glands of eyes and mouth.
- Graves' disease: an autoimmune condition resulting in hyperthyroidism, characterized by inflammation and congestion of periocular and orbital soft tissue.
- Systemic lupus erythematosus (SLE): a chronic inflammatory disease that can affect multiple organ systems, including the eyes.
Autoimmunity
- Autoimmunity is a misdirected immune response that occurs when the immune system attacks the body itself.
- It is a hypersensitivity reaction triggered by self-antigens.
- Molecular mimicry is a mechanism that can lead to autoimmunity, where a foreign antigen initiates an immune response, and a T- or B-cell component cross-recognizes self-antigens, leading to an autoimmune disease.
Tolerance
- The body has mechanisms to remove self-reactive T- and B-cells to prevent autoimmunity.
- Central tolerance is the mechanism that deletes self-reacting lymphocytes in the early stages of lymphocyte development (in thymus or bone marrow).
- Peripheral tolerance is a "safety net" that removes self-reactive lymphocytes that have escaped central tolerance, induced in mature lymphocytes, and involves T-regulatory cells (Tregs) that suppress autoreactions.
Classification of Autoimmune Conditions
- Autoimmune conditions are classified similarly to hypersensitivity reactions, with the exception of type I hypersensitivity.
- There are three types of autoimmune conditions:
- Antibody-mediated (Type II) hypersensitivity reactions
- Immune-complex mediated (Type III) hypersensitivity reactions
- Cell-mediated (Type IV) hypersensitivity reactions
Antibody-Mediated (Type II) Hypersensitivity Reactions
- Antibody-mediated reactions occur when an antibody reacts to self-antigens, binds to tissue/cells, and results in opsonisation and complement activation.
- Example: autoimmune haemolytic anaemia.
Immune-Complex Mediated (Type III) Hypersensitivity Reactions
- Immune-complex mediated reactions occur when immune complexes are not cleared rapidly, leading to inflammation and tissue damage.
- Example: systemic lupus erythematosus (SLE).
Cell-Mediated (Type IV) Hypersensitivity Reactions
- Cell-mediated reactions occur when autoimmune T-cell responses lead to inflammation and tissue damage.
- Examples: rheumatoid arthritis, type I diabetes mellitus.
Ocular Autoimmune Diseases
- Mooren's ulcer: a rare disorder characterized by a painful, relentless, chronic ulcerative keratitis.
- Sympathetic ophthalmia: a bilateral granulomatous uveitis that occurs after a penetrating injury to one eye, potentially blinding.
Systemic Autoimmune Diseases
- Keratoconjunctivitis sicca: a dry eye syndrome characterized by dryness, corneal examination may reveal punctate erosive keratopathy or filaments.
- Scleritis: inflammation of the sclera, characterized by pain, tenderness, and decreased vision.
- Rheumatoid arthritis: a chronic inflammatory disorder that affects the joints, skin, eyes, lungs, heart, and blood vessels.
- Sjögren's syndrome: an autoimmune condition characterized by dry eyes and a dry mouth, affecting the mucous membranes and moisture-secreting glands of eyes and mouth.
- Graves' disease: an autoimmune condition resulting in hyperthyroidism, characterized by inflammation and congestion of periocular and orbital soft tissue.
- Systemic lupus erythematosus (SLE): a chronic inflammatory disease that can affect multiple organ systems, including the eyes.
Ocular Manifestations of Autoimmune Diseases
- Keratoconjunctivitis sicca is a common ocular manifestation of autoimmune diseases, particularly in women over 40 years old.
- Treatment of keratoconjunctivitis sicca is symptomatic.
Rheumatoid Arthritis (RA)
- RA is a chronic inflammatory disorder primarily affecting the joints, but also affecting the skin, eyes, lungs, heart, and blood vessels.
- It is a cell-mediated (type IV) hypersensitivity reaction.
- Approximately 25% of patients with RA will have ocular manifestations, including:
- Keratoconjunctivitis sicca (most common, up to 25% of patients)
- Scleritis/episcleritis (4-10% of patients with RA)
- Keratitis
- Peripheral corneal ulceration
Graves' Disease
- Graves' disease is an autoimmune condition resulting in hyperthyroidism (overproduction of thyroid hormones).
- Inflammation and congestion of periocular and orbital soft tissue occur in Graves' disease.
- Ocular manifestations of Graves' disease include:
- Graves' ophthalmopathy
- Exposure keratopathy
- Diplopia
- Compressive optic neuropathy
Systemic Lupus Erythematosus (SLE)
- SLE is an autoimmune disease that occurs more frequently in women, particularly those of childbearing age.
- Ocular disease occurs in 20% of SLE patients, with external ocular manifestations including:
- Keratoconjunctivitis sicca
- Conjunctivitis
- Uveitis
- Episcleritis and scleritis
- Keratitis
- Discoid lupus rash over the eyelids
- Intraocular manifestations of SLE include:
- Microinfarction
- Hemorrhage
- Vasculitis in various locations
- Optic neuritis/optic neuropathy
Sympathetic Ophthalmia
- Sympathetic ophthalmia is a rare, bilateral, granulomatous uveitis that occurs after a penetrating injury to one eye.
- It is a potentially blinding disease that involves both eyes.
- More frequent in men, with a possible association with HLA-A11.
- Predisposing factors include:
- Penetrating injury (almost always occurs after a penetrating injury)
- Ciliary region wounds = dangerous zone
- Pathogenesis involves multiple theories, including the "allergic theory" and molecular mimicry.
Keratoconjunctivitis Sicca
- Keratoconjunctivitis sicca is a dry eye syndrome.
- Symptoms include:
- More prominent during the latter part of the day due to the evaporation of the tear film
- Corneal examination (slit lamp) may reveal punctate erosive keratopathy or filaments
Scleritis and Episcleritis
- Scleritis and episcleritis are distinguished based on anatomy and appearance.
- Symptoms may be similar, with scleritis having more severe pain and tenderness to palpation of the globe.
- Scleritis is more common in patients with RA, and patients with scleritis and RA have a worse prognosis.
Diabetes Mellitus (Type 1)
- Diabetes mellitus is an autoimmune condition where the insulin-producing cells in the pancreas are destroyed.
- It leads to elevated blood glucose levels and damages the blood vessels in most organ systems, including the eye.
- Ocular complications include:
- Diabetic retinopathy
- Cataract formation
- Glaucoma
- Prevention of complications involves controlling blood sugar levels and regular eye exams.
Sjögren's Syndrome
- Sjögren's syndrome is an autoimmune condition characterized by dry eyes and a dry mouth.
- It results in decreased production of tears and saliva due to molecular mimicry.
Classification of Autoimmune Conditions
- Autoimmune conditions are classified similarly to hypersensitivity reactions, with the exception of type I hypersensitivity.
- Types of autoimmune conditions include:
- Antibody-mediated (type II) hypersensitivity reactions
- Immune-complex mediated (type III) hypersensitivity reactions
- Cell-mediated (type IV) hypersensitivity reactions
Mooren's Ulcer
- Mooren's ulcer is a rare disorder characterized by a painful, relentless, chronic ulcerative keratitis.
- It typically occurs in healthy, adult men, with no evidence of systemic disease.
- Etiology is unsure, but possible autoimmune reactions include exposure to infectious agents.
Autoimmunity
- Tolerance is the mechanism for preventing autoimmunity, where self-reactive T- and B-cells are removed.
- Autoimmunity occurs when the immune system goes awry and attacks the body itself, triggering hypersensitivity reactions to self-antigens.
- Molecular mimicry is a process where foreign antigens initiate an immune response, leading to cross-reactive immune responses against self-antigens.
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Description
This quiz covers the basics of autoimmunity, including definitions, pathogenesis, and classification. It also explores ocular and systemic autoimmune conditions.
