Ocular Immune System Quiz
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Questions and Answers

What is the primary role of the tight junctions between endothelial cells in the blood vessels of the iris and retina?

  • To facilitate the passage of blood-borne molecules into the eye.
  • To promote rapid drainage of ocular fluids.
  • To restrict entry of immune cells and large molecules into the eye. (correct)
  • To actively transport nutrients to the retinal cells.

    • Why are there no patent lymphatic vessels within the anterior chamber, vitreous cavity, or retina of mammals?

  • To encourage direct transport of antigens to the trabecular meshwork.
  • To force antigen and APC transport via the bloodstream to the spleen rather than through lymphatic channels. (correct)
  • To reduce the reliance on the spleen for immune responses.
  • To prevent the flow of aqueous humor to the canal of Schlemm.

    • Which of the following does NOT contribute to the defense mechanisms of the ocular surface (cornea and conjunctiva) against external antigens?

  • The constant blinking to remove surface antigens.
  • The secretion of tears to irrigate and remove antigens.
  • The lymphatic drainage system in the cornea to filter pathogens. (correct)
  • The temperature of the central cornea.

    • What is the role of Langerhans cells in the conjunctival immune system?

    <p>To activate T and B cells by presenting phagocytosed antigens in draining lymph nodes.</p> Signup and view all the answers

    What is the primary route of drainage for the aqueous humour in the eye?

    <p>Through the trabecular meshwork into the canal of Schlemm.</p> Signup and view all the answers

    Which of the following best describes the immune response of the eye?

    <p>It is achieved via the limitation of immune cell entry, immune suppression and the presence of resident immune cells.</p> Signup and view all the answers

    The conjunctival MALT is mainly responsible for:

    <p>Mediating localized immune responses in the conjunctiva.</p> Signup and view all the answers

    Which of the following is NOT a primary function of the tear film in ocular surface defense?

    <p>Producing a cellular barrier with aggregated lymphocytes beneath the epithelium.</p> Signup and view all the answers

    What is the significance of the intact epithelial surface of the cornea and conjunctiva?

    <p>It physically restricts the penetration of pathogens.</p> Signup and view all the answers

    Where do the lateral and nasal portions of the conjunctiva primarily drain lymphatically?

    <p>The lateral portion drains into the preauricular lymph nodes, and the nasal portion drains into the submental lymph nodes.</p> Signup and view all the answers

    Which of these is NOT a component of the tear film's antibacterial arsenal?

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

    In the context of ocular surface defense, what is the primary role of sIgA?

    <p>To neutralize viruses and hinder bacterial adherence.</p> Signup and view all the answers

    What is a key characteristic of the sub-epithelial layer of the conjunctiva, especially during chronic infections?

    <p>It contains aggregated lymphocytes forming follicles.</p> Signup and view all the answers

    Which of the following best describes the function of ceruloplasmin in the tear film?

    <p>It plays a role in the removal of free radicals.</p> Signup and view all the answers

    What is most likely not implicated in the development of blepharitis?

    <p>High levels of sIgA in the tear film.</p> Signup and view all the answers

    What is the primary method by which the tear film combats foreign particles and bacteria on the ocular surface?

    <p>Forming a mechanical barrier via mucin and washing with tear flow.</p> Signup and view all the answers

    In cases of Fuch's heterochromic cyclitis (FHC), which cytokine is typically observed at increased levels?

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

    What is the primary characteristic of carcinoma-associated retinopathy (CAR) and melanoma-associated retinopathy (MAR)?

    <p>Circulating antibodies to tumour antigens that cross-react with retinal proteins</p> Signup and view all the answers

    Which cells are suggested to be involved with drusen development in age-related macular degeneration (AMD)?

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

    What is a commonality in the immunopathology observed in the choroid and retinal tissues during uveitis?

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

    Besides systemic diseases, what is another cause of posterior uveitis?

    <p>Idiopathic causes not related to systemic diseases</p> Signup and view all the answers

    What is the proposed mechanism behind the inflammatory response seen in retinitis pigmentosa?

    <p>Retinal antigen sensitisation</p> Signup and view all the answers

    What role does complement activation play in the development of age-related macular degeneration (AMD)?

    <p>Occurs both within the drusen and along the RPE-choroid interface</p> Signup and view all the answers

    What is the typical outcome of anti-retinal antibodies detected after laser photocoagulation of ischemic retina?

    <p>No effect on retinal function in most cases</p> Signup and view all the answers

    What is the primary function of the immune system in relation to the eye?

    <p>To establish a balanced response that targets pathogens while maintaining ocular transparency.</p> Signup and view all the answers

    Which type of cells are implicated in the tear production issues seen in early stages of some ocular conditions?

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

    What therapeutic approach has demonstrated success based on the content related to early gland destruction?

    <p>Topical cyclosporine</p> Signup and view all the answers

    Which of the following structures are not specifically mentioned in the text as having individual defense mechanisms?

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

    What is the primary characteristic of the immune response in individuals with Atopic Keratoconjunctivitis (AKC), as opposed to Vernal Keratoconjunctivitis (VKC)?

    <p>A marked TH1 response with increased IL-2 and IFN-γ secretion.</p> Signup and view all the answers

    Which cell type is primarily involved in T-cell interactions, potentially leading to fibrosis and scarring of the conjunctiva during inflammatory processes?

    <p>Conjunctival epithelial cells</p> Signup and view all the answers

    What common theme underlies the conditions mentioned when discussing the role of defense mechanisms?

    <p>They represent a range of disorders where immune response is a contributing factor.</p> Signup and view all the answers

    Which of the following conditions mentioned is NOT primarily associated with an autoimmune response?

    <p>Age-related macular degeneration (AMD)</p> Signup and view all the answers

    In the context of ocular surface disorders, what is a significant risk associated with using topical corticosteroids in individuals with AKC?

    <p>Increased risk of herpetic corneal infection.</p> Signup and view all the answers

    What is the main concern driving the need for a balanced immune response in the eye?

    <p>To prevent a response that would cause the eye tissue to become cloudy or lose transparency.</p> Signup and view all the answers

    Which of the following therapeutic agents is primarily responsible for reducing cytokine production by T cells and eosinophils in both VKC and AKC?

    <p>Topical cyclosporin</p> Signup and view all the answers

    What is the primary source of cellular corneal defense given the cornea's avascular nature?

    <p>Lymphocytes and Langerhans cells located in the limbus and from the anterior chamber.</p> Signup and view all the answers

    According to content, what is the focus of the subsequent module (Unit 3) following the discussion of the immune system and ocular abnormalities?

    <p>Microbiology and clinical laboratory testing</p> Signup and view all the answers

    What is a main characteristic of non-infectious immune-related responses of the cornea?

    <p>They mainly occur in the area immediately adjacent to the limbus.</p> Signup and view all the answers

    In which specific situation is the systemic immune system known to have prior contact with ocular antigens, potentially leading to a more pronounced immune response?

    <p>Following corneal transplant, or regrafting.</p> Signup and view all the answers

    Which of the following statements best describes the relationship between HLA-DR antigen expression and the growth rate of a pterygium?

    <p>Increased expression of HLA-DR antigens seems to be correlated with the growth rate of lesion.</p> Signup and view all the answers

    Which of the following is a characteristic feature of Miller Fisher syndrome?

    <p>A triad of ataxia, ophthalmoplegia, and reduced or absent tendon reflexes.</p> Signup and view all the answers

    In orbital myositis, what is a common symptom, according to the text?

    <p>Pain on ocular movement accompanied by swelling on imaging.</p> Signup and view all the answers

    Which of the following cell types is most commonly involved in the infiltration of orbital tissue in thyroid eye disease?

    <p>Lymphocytes and macrophages</p> Signup and view all the answers

    Besides idiopathic causes, what is another potential cause of orbital myositis?

    <p>Systemic inflammation or infection.</p> Signup and view all the answers

    What is the key autoantibody found in Miller Fisher syndrome?

    <p>Anti-GQ1b IgG.</p> Signup and view all the answers

    Which of these is a characteristic of thyroid-associated ophthalmopathy regarding the extraocular muscles?

    <p>Lymphocytic infiltration of the extraocular muscles.</p> Signup and view all the answers

    What is a key feature of the pathophysiology of myasthenia gravis, based on the material?

    <p>Antibodies blocking the acetylcholine receptors at the nerve-muscle synapses.</p> Signup and view all the answers

    What is a typical characteristic finding in the extraocular muscles of patients with early thyroid associated ophthalmopathy?

    <p>An interaction between T-cells and fibroblasts.</p> Signup and view all the answers

    Study Notes

    Ocular Immune System

    • The eye has mechanisms to protect itself from pathogens, known as immune privilege. This involves limited inflammatory responses and modified immunity.
    • Factors contributing to immune privilege include a blood-ocular barrier, composed of tight junctions that prevent blood-borne immune cells from entering the eye, and the absence of lymphatic vessels. Instead, the spleen plays the main role in processing antigens.
    • Cells lining the anterior chamber and subretinal space actively suppress responses to intraocular antigens, a process called Anterior Chamber Associated Immune Deviation (ACAID).
    • Tears act as a barrier against foreign antigens through mechanical removal, temperature inhibition of microbes, and irrigation.
    • The cornea and conjunctiva have immune cells that protect against pathogens, including Langerhans cells, T cells, and B cells.
    • The tear film components like slgA, IgG, IgE, lysozyme, lactoferrin, transferrin, and complement protect against microbes.
    • Blepharitis, an inflammation of the eyelid margins, is frequently associated with bacterial infections, particularly staphylococci.
    • Conjunctival scarring can occur in certain inflammatory conditions, impacting the lacrimal glands (leading to dry eye)

    Tear Film and Function

    • The tear film protects the ocular surface in four ways: trapping foreign particles with mucins, washing away microbes, containing antimicrobial proteins (like lysozyme), and containing immune cells.
    • Specific proteins are crucial for tear film function in protecting the eye.

    Corneal Immunology

    • The cornea is avascular, so defence relies on the limbus and anterior chamber.
    • Non-infectious corneal inflammatory disorders like Mooren's ulcer and Terrien's marginal degeneration can occur.
    • Viral infections (like herpes simplex) can have an immune response. This response can be mild or significant.
    • Corneal transplantation has a high success rate due to corneal avascularity and lack of immune cell activation. This can be impaired/lower in conditions where the integrity of the vasculature is affected.

    Scleral Immunology

    • Sclera inflammation (scleritis) can have different localizations and causes. This can effect the cornea (leading to melt).
    • Systemic diseases (like rheumatoid arthritis, SLE, Wegener's granulomatosis, and PAN) and infections (like acanthamoeba) can be associated with scleritis.

    Immunology of the Uvea

    • The uvea (iris, ciliary body, choroid) has limited lymphatic drainage and tight junctions to prevent immune infiltration.
    • Inflammation in the uvea (uveitis) can have various causes and involve different immune cells.
    • Acute anterior uveitis, involving PMNs and T cells is common, typically characterized by a red eye.
    • A variety of ocular inflammations can occur elsewhere affecting the uvea, and potentially involve systemic diseases.

    Immunology of the Neuroretina and RPE

    • The neuroretina has antigen components, including retinal s-antigen and IRBP, that can trigger an immune response.
    • The retina's immune response is complex, possibly related to systemic issues like melanoma-associated retinopathy.

    Immunology of the Orbit

    • The optic nerve can be affected by inflammation, sometimes associated with multiple sclerosis, with an immune response similar to conditions in the brain.
    • Grave's disease, characterized by exophthalmos, involves the extraocular muscles and orbital fat, which are infiltrated by T cells.
    • Myasthenia gravis, results in weakness of the muscles, because of antibodies targeting the acetylcholine receptor. Damage to the muscles can lead to strabismus (eye misalignment).
    • Orbital myositis involves inflammation of the orbital muscles, either idiopathic or associated with systemic diseases or infection.

    Dry Eye and Role of the Lacrimal Gland

    • Damage to the lacrimal gland (part of the tear production system) results in decreased tear volume and changes in tears. This is observed in some dry eye syndromes, like Sjögren syndrome and sarcoidosis.
    • T cell activation is suspected to cause tear production issue and destruction of the secretory cells (acinar) in the early stages of the issue, possibly respondable to treatment (like topical cyclosporin).

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    Description

    Test your knowledge on the ocular immune system and its mechanisms for protecting the eye from pathogens. This quiz covers concepts like immune privilege, the blood-ocular barrier, and the role of tears and immune cells in ocular defense. Dive into the intricacies of the eye's defense mechanisms!

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