Immunology of the Eye
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Questions and Answers

What is the mechanism of immune privilege that prevents the passage of cells from the blood to the anterior eye?

  • Immunosuppressive molecules
  • Lymphatic drainage
  • Tight junctions between cells (correct)
  • Major histocompatibility (MHC) molecules

    • The eye has a well-developed lymphatic drainage system.

    False

    What is the result of exposure of the anterior chamber to a foreign antigen?

    Induction of suppressor immunity

    Anterior chamber-associated immune deviation (ACAID) is mediated by specific _______________ and NKT cells.

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

    What is the function of immunosuppressive molecules in the eye?

    <p>To inhibit T-cell proliferation</p> Signup and view all the answers

    Match the following mechanisms of immune privilege with their descriptions:

    <p>Anatomical features = Protected by conjunctiva and eyelids Lack of lymphatic drainage = Prevents antigen presentation to immune cells Immunosuppressive molecules = Inhibit T-cell proliferation and suppress interferon secretion Development of tolerance = Induces suppressor immunity</p> Signup and view all the answers

    The eye has a high expression of major histocompatibility (MHC) molecules.

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

    What is the result of induction of antigen-specific suppressor CD8+ T-cells and regulatory T-cells?

    <p>Suppressor immunity</p> Signup and view all the answers

    What is the mechanism by which the host epithelium responds to a graft in epithelial rejection?

    <p>The host epithelium grows inward from the remaining host cornea and limbus, covering the graft</p> Signup and view all the answers

    The presence of bone marrow-derived cells in the host cornea at the time of surgery contributes to a lower rejection rate.

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

    What is the primary function of the immune cells recruited into the cornea through limbal circulation?

    <p>To process and present antigens</p> Signup and view all the answers

    What is the result of the proliferation of T-regulatory cells specific to the antigen?

    <p>Suppresses the delayed type hypersensitivity (Type IV) response</p> Signup and view all the answers

    Corneal transplantation is not a successful procedure.

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

    The capacity of the graft to induce _______________________ is a mechanism that contributes to immune privilege.

    <p>anterior chamber-associated immune deviation (ACAID)</p> Signup and view all the answers

    Which type of rejection is characterized by subepithelial infiltrates with leukocytes?

    <p>Subepithelial rejection</p> Signup and view all the answers

    What is the main reason for avoiding immune response in the eye?

    <p>To prevent dysfunction, such as loss of vision, due to inflammation</p> Signup and view all the answers

    What is the role of the aqueous humor in maintaining immune privilege in the eye?

    <p>It creates an immunosuppressive local microenvironment</p> Signup and view all the answers

    The absence of __________ vessels in the graft and its bed contributes to immune privilege.

    <p>blood and lymph</p> Signup and view all the answers

    Match the following immune response mechanisms with their functions:

    <p>Anterior Chamber-associated Immune Deviation = Suppresses immune response in the eye Mechanisms Of Immune Privilege = Prevents inflammation in the eye Lymphatic Drainage In The Eye = Drains excess fluids from the eye Immunosuppressive Molecules = Suppresses the immune response</p> Signup and view all the answers

    Match the following types of rejection with their characteristics:

    <p>Epithelial rejection = Host epithelium grows inward from remaining host cornea and limbus Subepithelial rejection = Subepithelial infiltrates with leukocytes Both types of rejection = Steroid responsive, generally self-limited, and tend not to cause visual disturbance</p> Signup and view all the answers

    The presence of MHC-antigens on graft cells enhances immune privilege in the eye.

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

    What is the name of the surgical procedure that involves replacing the diseased or damaged cornea with a healthy donor cornea?

    <p>All of the above</p> Signup and view all the answers

    The eye has a well-developed lymphatic drainage system.

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

    What is the indication for corneal transplantation when the cornea is likely to break open?

    <p>Severe scarring of cornea</p> Signup and view all the answers

    What is the primary function of immune privilege?

    <p>To protect vital structures from the potentially damaging effects of an inflammatory immune response</p> Signup and view all the answers

    The anterior chamber is not immune privileged.

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

    What is an allograft?

    <p>A transplant of an organ or tissue from one individual to another of the same species with a different genotype.</p> Signup and view all the answers

    The eye is protected from immune reactions that are potentially dangerous in the _______________________ chamber.

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

    Which of the following is NOT an example of an immune privileged site?

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

    Corneal graft rejection is a major concern in eye transplantation.

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

    Match the following immune privileged sites with their characteristics:

    <p>Eyes = Protected from immune reactions that are potentially dangerous Placenta and fetus = Immune responses directed against a fetus can lead to the loss of the fetus Brain = Inflammation in the brain can lead to loss of organ function Testicles = Hair growth is promoted</p> Signup and view all the answers

    What is the purpose of immune privilege in the eye?

    <p>To protect the eye from the potentially damaging effects of an inflammatory immune response.</p> Signup and view all the answers

    What is the primary mechanism of direct pathway in corneal graft rejection?

    <p>Donor's APCs are recognised directly by recipient's T-cells</p> Signup and view all the answers

    Corneal graft rejection is always symptomatic.

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

    What are the two mechanisms of corneal graft rejection?

    <p>Direct pathway and indirect pathway</p> Signup and view all the answers

    The indirect pathway of corneal graft rejection leads to ______ hypersensitivity.

    <p>Delayed (Type IV)</p> Signup and view all the answers

    Match the following risk factors with their corresponding descriptions:

    <p>Host corneal vascularisation = Lower risk with this age group Larger and eccentric grafts = Increased risk of graft rejection Presence of donor epithelium upon transplantation = Increased risk of graft rejection due to presence of donor cells Age &gt; 60 years = Increased risk of graft rejection due to increased blood supply</p> Signup and view all the answers

    What is the primary site of antigen processing in corneal graft rejection?

    <p>At cornea, ocular environments, and draining lymph nodes</p> Signup and view all the answers

    ABO blood type incompatibility is a confirmed risk factor for corneal graft rejection.

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

    What is the common complaint associated with corneal graft rejection?

    <p>Decrease in visual acuity, redness, pain, irritation, and photophobia</p> Signup and view all the answers

    Study Notes

    Mechanisms of Immune Privilege

    • Lack of lymphatic drainage in the eye
    • Anatomical features: blood barrier, no blood vessels or inflammatory cells, protected by conjunctiva and eyelids
    • Presence of immunosuppressive molecules or cell surface receptors that inhibit T-cell proliferation and suppress interferon secretion
    • Lower expression of major histocompatibility (MHC) molecules
    • Development of tolerance against antigens through anterior chamber-associated immune deviation (ACAID)

    Anterior Chamber-Associated Immune Deviation (ACAID)

    • Exposure of the anterior chamber to a foreign antigen induces suppressor immunity
    • Induction of antigen-specific suppressor CD8+ T-cells and regulatory T-cells (suppressor CD4+ T-cells)
    • Induction of non-complement-fixing antibodies mediated by specific macrophages
    • Presentation of inoculated antigen to a cluster of B-cells, NKT cells, CD4+ and CD8+ T cells in the spleen

    Corneal Graft Rejection

    • Types of rejection: epithelial, subepithelial, and both types
    • Immune mechanism: inflamed cornea contributes to erosion of immune privilege
    • Bone marrow-derived cells are recruited into cornea through limbal circulation
    • These cells can process and present antigens, leading to rejection

    Why Immune Privilege?

    • Normal symptoms of inflammation (redness, swelling, and pain) can lead to dysfunction in the eye (loss of vision)
    • Certain circumstances (e.g., trauma, infection, genetics) can lead to dysfunction of the regulatory mechanisms of the eye, leading to immune inflammatory diseases

    Corneal Transplantation

    • Also known as penetrating keratoplasty
    • Over 40,000 procedures done per year in the USA
    • Indications: severe scarring of cornea, cornea likely to break open, severe damage involving cornea and lens
    • Corneas are removed from donors who have been declared dead

    Why is Corneal Transplantation Successful?

    • Due to corneal immune privilege
    • Absence of blood and lymph vessels in the graft and its bed
    • Absence of MHC class II+ antigen presenting cells in the graft

    Risk Factors for Corneal Graft Rejection

    • Host corneal vascularisation
    • Larger and eccentric grafts
    • Presence of donor epithelium upon transplantation
    • History of previous graft failure of any cause
    • Bilateral penetrating keratoplasty
    • Pre-transplantation corneal tissue media and preservation
    • Host age (lower risk with age >60 y, much higher risk in infants)
    • Human leukocyte antigen A (HLA-A) and human leukocyte antigen (HLA-B) and ABO blood type incompatibility

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    Related Documents

    Ocular Immune Privilege and Corneal Transplantation PDF

    Description

    This quiz covers the mechanisms of immune response in the eye, including the lack of lymphatic drainage, anatomical features, and the presence of immunosuppressive molecules. It also explores the development of tolerance against antigens and the role of MHC molecules.

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