Ocular Immunology and Immune Privilege
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Questions and Answers

Which cell type is NOT primarily associated with acute cicatricial pemphigoid?

  • Macrophages
  • Neutrophils
  • T cells (helper and cytotoxic)
  • B cells (correct)

    • In acute allergic conjunctivitis, which mechanism leads to the release of histamine?

  • IgE binding to mast cells followed by allergen interaction. (correct)
  • T cell-mediated cytokine release
  • Direct activation of mast cells by allergens.
  • IgG binding to mast cells.

    • Which of the following is characteristic of chronic allergic conjunctivitis?

  • Dominant type 1 hypersensitivity reaction
  • Exclusive mast cell activation
  • T-cell response in addition to mast cells and eosinophils (correct)
  • Primary involvement of neutrophils and macrophages

    • Which of the following best describes the cytokine profile of Atopic Keratoconjunctivitis (AKC)?

    <p>Primarily TH2 mediated with IL-2 and interferon-gamma.</p> Signup and view all the answers

    What distinguishes pterygium from pinguecula based on the content provided?

    <p>Pterygia express HLA-DR, a class II MHC molecule, while pinguecula do not.</p> Signup and view all the answers

    Which of the following is a non-infectious corneal condition that primarily affects the area adjacent to the limbus?

    <p>Mooren's ulcer</p> Signup and view all the answers

    What is the main reason stated that corneal transplants have a high success rate?

    <p>Corneal avascularity and limited immune response.</p> Signup and view all the answers

    Which of the following is NOT mentioned as a factor that can reduce the success rate of corneal transplantation?

    <p>Pre-existing high levels of Langerhans cells in the cornea.</p> Signup and view all the answers

    Which immunosuppressive drugs are typically used for a year following a graft?

    <p>Cyclosporin and mycophenolate</p> Signup and view all the answers

    What is the primary structural component of the sclera?

    <p>Collagen fibres</p> Signup and view all the answers

    Which of the following cells is NOT a main inflammatory cell type found in the sclera?

    <p>Eosinophils</p> Signup and view all the answers

    What primary feature of the iris and ciliary body maintains the blood-aqueous barrier?

    <p>Low permeability of blood vessels and tight junctions</p> Signup and view all the answers

    Which cytokine is typically elevated and down-regulates inflammation in less aggressive forms of uveitis, like Fuch's Heterochromic Cyclitis?

    <p>IL-10</p> Signup and view all the answers

    In posterior uveitis, which cell type is primarily associated with the production of cytokines and activation of macrophages?

    <p>CD4+ T cells</p> Signup and view all the answers

    Which component of the tear film primarily functions by trapping microorganisms?

    <p>Tear film and mucin glycoproteins</p> Signup and view all the answers

    Which condition is characterized by an immune response in one eye following penetrating trauma, leading to bilateral inflammation?

    <p>Sympathetic ophthalmia</p> Signup and view all the answers

    Which of the following is NOT identified as a potential immunological target in the neuroretina and RPE?

    <p>Melanin</p> Signup and view all the answers

    Which of these is NOT a function of sIgA in the tear film?

    <p>Facilitates cell lysis</p> Signup and view all the answers

    In age-related macular degeneration (AMD), which immune components are primarily found within drusen and the RPE-choroid interface?

    <p>Dendritic cells and complement components</p> Signup and view all the answers

    Which antibody is typically found in the tear film only during pathological circumstances?

    <p>IgG</p> Signup and view all the answers

    What is the primary role of lactoferrin in the tear film?

    <p>Chelating iron and destabilizing bacterial membranes</p> Signup and view all the answers

    Which of the following is primarily associated with optic neuritis?

    <p>T-cell involvement</p> Signup and view all the answers

    Which of the following is a function of ceruloplasmin in the tear film?

    <p>Free radical removal</p> Signup and view all the answers

    Which cell type is responsible for phagocytosing antigens in the conjunctival MALT?

    <p>Langerhans cells</p> Signup and view all the answers

    Where do the lateral and nasal conjunctiva drain, respectively?

    <p>Periauricular and submental lymph nodes</p> Signup and view all the answers

    What is the main immune cell involved in chronic blepharitis?

    <p>T-cells</p> Signup and view all the answers

    The complement system in tear film contributes to defense how?

    <p>Cell lysis</p> Signup and view all the answers

    What is the main purpose of immune privilege in the eye?

    <p>To minimise the immune response and protect the eye.</p> Signup and view all the answers

    Which of these is NOT a mechanical barrier for microbes?

    <p>Blinking</p> Signup and view all the answers

    Which of the following is NOT a site of immune privilege in the eye?

    <p>Retina</p> Signup and view all the answers

    What type of junctions are primarily responsible for restricting the entry of blood-borne molecules into the eye?

    <p>Zonula occludens junctions</p> Signup and view all the answers

    What is the main role of the blood ocular barrier?

    <p>To prevent the entry of blood-borne molecules and cells involved in immune responses</p> Signup and view all the answers

    How does the anterior chamber drain?

    <p>Into the venous system</p> Signup and view all the answers

    Which of the following statements is TRUE regarding lymphatic vessels in the eye?

    <p>Patent lymphatic vessels have not been demonstrated in the anterior chamber, vitreous, or retina of mammals.</p> Signup and view all the answers

    Where does the primary immune response to intraocular antigens occur?

    <p>Spleen</p> Signup and view all the answers

    What contributes to the immunosuppressive microenvironment of the anterior chamber and subretinal space?

    <p>The synthesis of immunosuppressive substances by lining cells.</p> Signup and view all the answers

    What does the abbreviation 'ENDORI' refer to in the context of the blood ocular barrier?

    <p>Endothelial cells in the blood vessels of the iris and retina</p> Signup and view all the answers

    What is the primary function of Anterior Chamber Associated Immune Deviation?

    <p>To suppress the immune system</p> Signup and view all the answers

    Which of the following is a characteristic feature of extraocular muscle (EOM) involvement in an autoimmune process?

    <p>Increased muscle fiber size due to lymphocytic infiltration.</p> Signup and view all the answers

    In myasthenia gravis, what is the primary mechanism leading to muscle weakness?

    <p>Antibodies targeting the acetylcholine receptors at the synapses.</p> Signup and view all the answers

    A patient presents with ataxia, ophthalmoplegia, and diminished tendon reflexes. Which syndrome is most likely the cause?

    <p>Miller Fisher Syndrome</p> Signup and view all the answers

    What is the primary target of the autoimmune reaction in the lacrimal gland?

    <p>The lacrimal acinar cells responsible for aqueous tear secretion.</p> Signup and view all the answers

    Which of the following immune cells are predominantly involved in blepharitis?

    <p>T cells</p> Signup and view all the answers

    Which cells are primarily involved in cicatricial pemphigoid?

    <p>Macrophages, neutrophils, T cells (CD4+ and CD8+), and limited B cells</p> Signup and view all the answers

    What is the primary immunoglobulin involved in allergic conjunctivitis?

    <p>IgE</p> Signup and view all the answers

    What type of T helper cell is primarily involved in vernal keratoconjunctivitis (VKC)?

    <p>TH2</p> Signup and view all the answers

    In atopic keratoconjunctivitis, which additional immune mediator is notably involved alongside mast cells and eosinophils?

    <p>IL-2 and IF-GAMMA</p> Signup and view all the answers

    Which condition is characterised by HLA-DR, Ki-67, and PCNA expression?

    <p>Pterygium</p> Signup and view all the answers

    Scleritis and episcleritis share which common set of immune cells?

    <p>T cells (primarily CD4+) and macrophages</p> Signup and view all the answers

    A patient presents with HLA B27 positivity, and uveitis. Which cytokine is likely to be involved alongside these findings?

    <p>IL-10</p> Signup and view all the answers

    In sympathetic ophthalmia, what is the predominant T-cell subtype involved?

    <p>CD4+</p> Signup and view all the answers

    Which set of immune components are implicated in Age related macular degeneration(AMD)?

    <p>IgA, IgG, IgE, C1q, C3c and C3d</p> Signup and view all the answers

    Which condition is associated with melanin associated antigens?

    <p>VKH Syndrome</p> Signup and view all the answers

    Study Notes

    Ocular Immune Privilege

    • Eyes avoid immune system response to protect from pathogens
    • Immune privilege sites include cornea and anterior chamber
    • Factors contributing to immunity privilege include zonula occluden junctions.
    • These junctions prevent blood-borne molecules and cells from entering the eye.
    • Absence of lymphatic vessels in the anterior chamber, vitreous humour, and retina.
    • Antigens and antigen-presenting cells (APCs) travel to the spleen, instead of regional lymph nodes.

    Blood Ocular Barrier

    • Endothelial cells in blood vessels of the iris and retina
    • Epithelial cells in the ciliary body and retina
    • These barriers prevent blood-borne molecules and cells which participate in innate and adaptive immunity from entering the eye

    Anterior Chamber Associated Immune Deviation

    • Cells lining the anterior chamber and subretinal space produce substances that suppress the immune system.
    • These substances actively contribute to a microenvironment that suppresses immune responses.

    Cornea and Conjunctiva

    • Cornea and conjunctiva are constantly under threat from foreign substances.
    • Tear irrigation, blinking, and high cornea temperature eliminate microbes from the eye.
    • Intact epithelial surface prevents pathogen influx.

    Tear Film

    • Mechanical barrier traps microbes
    • Regular washing of tears removes microbes
    • Polymorphonuclear leukocytes present in tears fight microbes
    • Tear film contains many antibacterial proteins
    • Ceruloplasmin: free radical removal
    • Complement: complement cascade, cell lysis
    • slgA: secreted antibody, virus neutralisation, inhibits bacterial adherence
    • IgE: Normal levels are low, increase in allergic responses
    • IgG: antigen specific antibody
    • Lysozyme: proteolytic enzyme/ facilitates IgA bacteriolysis
    • Lactoferrin: chelation of iron, destabilization of bacterial membranes
    • Transferrin: iron chelator, antioxidant effect

    Conjunctival Immune System (Conjunctival MALT)

    • Main players like Langerhans cells, phagocytose antigens
    • Lateral conjunctiva drains to periauricular lymph nodes
    • Nasal conjunctiva drains to submental lymph nodes
    • Conjunctiva has B cells and T cells in subepithelial layers
    • Mast cells, PMNs, and eosinophils also present in the subepithelial layer
    • Chronic infections lead to follicular conjunctivitis formation, lymphocytes aggregate

    Blepharitis

    • Chronic condition, T cells are the main immune cells
    • May be linked to bacteria like staphylococci

    Cicatricial Pemphigoid Membrane

    • Scarring and cicatrisation
    • Symptomatic
    • Can be associated with scarring in the mouth
    • Linear deposition of antibodies to basement membrane zone
    • Acute disease involves macrophages and neutrophils, helper and cytotoxic T cells, a few B cells

    Allergic Conjunctivitis

    • Type 1 hypersensitivity reactions
    • Seasonal (pollen)
    • Perennial (house dust mites)
    • Can be triggered by eye drops preservatives
    • Mast cells and eosinophils
    • IgE with mast cells bind to allergen
    • Histamine is released

    Chronic Allergic Conjunctivitis

    • Giant papillary conjunctivitis, Vernal keratoconjunctivitis, atopic keratoconjunctivitis
    • Mast cells, eosinophils, and a T cell response
    • TH1 response in vernal keratoconjunctivitis and giant papillary conjunctivitis
    • TH2 response in atopic keratoconjunctivitis
    • AKC and VKC patients may be at risk of herpetic corneal infections (bilateral)
    • Giant papillary conjunctivitis (GPC) isn't associated with atopy, more with artificial devices.

    Pterygium

    • Common in hot climates
    • Thought that immune mechanisms may be involved in its formation
    • Class 2 MHC molecule HLA-DR is abundantly expressed in pterygium epithelial cells, it isn’t found in pinguecula
    • Increased CD4+ and PCNA expressions in pterygium

    Cornea

    • Defence comes from the surrounding limbus and anterior chamber
    • Limbus contains lymphocytes and Langerhans cells (rare in normal cornea, increase in infectious conditions)
    • Disorders like Mooren's ulcer, Terrien's marginal degeneration, Wegener's granulomatosis and acne rosacea affect cornea, nearby sclera.
    • Viral infections (herpes simplex) and other infections can affect the cornea and lead to uveitis

    Corneal Transplantation Success Rate

    • 90% success rate
    • Reduced success in immunocompromised patients
    • Cornea lack of blood vessels, immune activation
    • Factors like immunocompromised patients and corneal neovascularization affect success rate

    Graft Rejection

    • Topical and possibly systemic corticosteroid therapy used

    Immunology of the Sclera

    • Mainly composed of collagen fibers
    • Opaque and covered by episclera
    • Main Inflammatory cells include: T (Th cells), macrophages, and clusters of B cells, neutrophils, and plasma cells

    Immunology of the Uvea

    • Highly vascularized tissue (iris, ciliary body, choroid)
    • Missing lymphatic vessels, low iris blood-vessel permeability, tight junctions (BAB and BRB)
    • Pathological conditions can alter barriers, allowing leukocyte migration and increased vascular permeability
    • Acute uveitis involves PMNs and T cells migrating to the anterior chamber
    • HLA B27 is positive in 60% cases of acute uveitis
    • Chronic uveitis is not typically HLA B27 positive, but may be associated with other disorders.

    Posterior Uveitis

    • Inflammation can occur in the retina and scleral tissue, caused by various factors
    • Systemic diseases (sarcoidosis and Behcet's disease) can be a cause
    • CD4+ T cells produce cytokines, activated macrophages with HLA DR upregulation
    • CD8+ T cells and B cells are also involved.

    Immunology of the Neuroretina and RPE

    • Antigens such as retinal S-antigen, interphotoreceptor retinol binding protein and rhodopsin
    • Retinitis pigmentosa may result from retinal antigen sensitisation
    • Laser photocoagulation of ischemic retina, anti-retinal antibodies but minimal effect on retinal function

    Immunology of Extraocular Constituents

    • Optic neuritis (MS, T-cells implicated)
    • Graves disease (EOMs and orbital fat enlargement with T-cells, CD4 and CD8)
    • Myasthenia gravis (Muscle weakness, antibodies against acetylcholine receptor)
    • Miller Fisher syndrome (Characterized by ataxia, ophthalmoplegia, reduced/absent tendon reflexes, anti-GQ1B IgG)
    • Lacrimal gland (Autoimmune reaction, affecting aqueous tear component, reducing tear volume)

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    Ocular Immune System PDF

    Description

    Explore the fascinating concepts of ocular immune privilege and the mechanisms that protect the eye from immune responses. This quiz covers the blood-ocular barrier, anterior chamber associated immune deviation, and the unique factors that contribute to the eye's specialized immune environment. Test your knowledge on how these processes prevent pathogens from affecting vision.

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