Antimicrobial Peptides in Epithelial Cells
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Questions and Answers

What is the primary function of Paneth cells in the gastrointestinal tract?

  • Secretion of antimicrobial peptides (correct)
  • Differentiation of T cells
  • Production of mucus
  • Sampling antigens

    • Which of the following best describes the role of M cells in Peyer's patches?

  • Sampling antigens (correct)
  • Differentiating T cells
  • Regulating macrophage activity
  • Producing mucus

    • Which T helper cell type is primarily activated by IL-4 and targets extracellular pathogens?

  • Th1
  • Th2 (correct)
  • Treg
  • Th17

    • What is an essential function of Langerhans cells in the oral mucosa?

    <p>Endocytosis of pathogens</p> Signup and view all the answers

    Which cytokine primarily initiates the activation of T regulatory cells (Tregs)?

    <p>TGF-β</p> Signup and view all the answers

    What molecule do Th17 cells produce to stimulate neutrophil recruitment?

    <p>IL-8</p> Signup and view all the answers

    Which lymphocyte type is responsible for the immune suppression that involves pushing towards the M2 phenotype?

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

    Which cytokine is associated with the activation of macrophages by Th1 cells?

    <p>IFN-γ</p> Signup and view all the answers

    What is the main role of tight junctions in the gastrointestinal tract's epithelial lining?

    <p>Prevent leakage between cells</p> Signup and view all the answers

    Which type of immunity is primarily mediated by Th1 cells?

    <p>Intracellular pathogen destruction</p> Signup and view all the answers

    Which of the following antimicrobial peptides are effective specifically against Candida albicans?

    <p>Histatin-5</p> Signup and view all the answers

    What is the main function of defensins produced by epithelial cells?

    <p>Disrupting microbial membranes and providing antibacterial properties</p> Signup and view all the answers

    Which antimicrobial peptide acts primarily as a chelator of Fe3+ and inhibits the metabolic activity of microorganisms?

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

    What characteristic of secretory IgA contributes to its effectiveness in saliva?

    <p>Inhibits adherence and agglutinates bacteria</p> Signup and view all the answers

    Which antimicrobial peptide’s activity can be classified under hydrolyzing glycosidic bonds to damage bacterial cell walls?

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

    Which means of action is associated with the Myeloperoxidase system in saliva?

    <p>Bactericidal in presence of thiocyanate/halide-H2O2</p> Signup and view all the answers

    What role do cystatins play in oral mucosa?

    <p>Inhibition of microbial protease</p> Signup and view all the answers

    Considering the leukocyte composition in oral mucosa, which statement is true?

    <p>Up to 50% of the leukocytes may lack phagocytic capability.</p> Signup and view all the answers

    Which antimicrobial mechanism is primarily offered by Chitinase?

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

    Which type of defensins specifically include HNP-1 to HNP-4?

    <p>Alpha-defensins</p> Signup and view all the answers

    Which antimicrobial peptide is primarily known for its antifungal properties against Candida albicans?

    <p>Histatin-5</p> Signup and view all the answers

    What is one role of cathelicidin (LL-37) in the oral mucosa?

    <p>Wound healing and immunomodulation</p> Signup and view all the answers

    Defensins are known to act against which types of microorganisms?

    <p>Both Gram-positive and Gram-negative bacteria</p> Signup and view all the answers

    Which peptide is primarily involved in inhibiting the metabolic activity of microorganisms by chelating Fe3+?

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

    What do histatins primarily inhibit in the oral mucosa?

    <p>Candida albicans</p> Signup and view all the answers

    Which component is a glycoprotein that contributes to the agglutination of bacteria in saliva?

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

    Which of the following is NOT a function of secretory IgA in saliva?

    <p>Enhances cytokine release</p> Signup and view all the answers

    Which antimicrobial mechanism is associated with lysozyme in the oral mucosa?

    <p>Hydrolyzes glycosidic bonds</p> Signup and view all the answers

    Which type of leukocyte is predominant in the oral mucosa?

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

    Which antimicrobial peptide operates through the myeloperoxidase system in the presence of thiocyanate/halide-H2O2?

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

    What is one function of Langerhans cells in the oral mucosa?

    <p>Endocytose antigens and present them to T cells</p> Signup and view all the answers

    Which T helper cell type is associated with mucosal immunity and is activated by TGF-β?

    <p>Th17</p> Signup and view all the answers

    Which cytokine is primarily responsible for activating macrophages in response to Th1 cells?

    <p>IFN-γ</p> Signup and view all the answers

    What is the primary role of the specialized lymphoid tissues known as Peyer's patches in the gastrointestinal tract?

    <p>Sampling antigens to trigger immune responses</p> Signup and view all the answers

    What distinguishes Treg cells from other T helper cell types in terms of function?

    <p>They suppress immune responses and promote tolerance.</p> Signup and view all the answers

    Which receptor type on lymphocytes is responsible for sensing specific chemical signals during lymphocyte homing?

    <p>Chemokine receptors</p> Signup and view all the answers

    Which cytokine is specifically produced by Th2 cells to enhance B cell responses?

    <p>IL-4</p> Signup and view all the answers

    What is a key characteristic of the lamina propria in relation to immune function?

    <p>Role in T cell differentiation and IgA production</p> Signup and view all the answers

    What is the role of the antimicrobial peptides (AMPs) in the gastrointestinal tract?

    <p>They provide defense against both extra- and intracellular pathogens.</p> Signup and view all the answers

    Which cytokine does Th17 produce that is critical for recruiting neutrophils?

    <p>IL-17A</p> Signup and view all the answers

    Study Notes

    Epithelial barrier function and antimicrobial peptides

    • Epithelial cells produce a variety of antimicrobial peptides (AMPs) that are important for the innate immune system.
    • Defensins (α- and β-) are effective against both Gram-positive and Gram-negative bacteria.
    • Cathelicidin (LL-37) shows antimicrobial, immunomodulatory, and wound-healing properties.
    • Histatins, particularly histatin-5, are antifungal AMPs.

    AMPs in the Oral Cavity

    • Saliva contains a range of AMPs with diverse functions.
    • α-Amylase inhibits P. gingivalis.
    • Defensins (α and β) exhibit antibacterial, antiviral, and immunomodulatory properties.
    • Cystatins and secretory leukocyte protease inhibitor inhibit microbial protease activity.
    • Histatins 1, 3, and 5 inhibit Candida albicans.
    • Chitinase possesses antifungal activity with cell wall lysis capabilities.
    • Statherin inhibits anaerobic bacterial growth.
    • Secretory IgA (sIgA) is the major antibody in saliva and plays a role in bacterial adherence inhibition, agglutination, and virus neutralization.
    • Lactoferrin is an iron-chelating protein that inhibits microbial metabolic activity.
    • Lysozyme hydrolyzes the glycosidic bond in bacterial cell walls, particularly effective against S. mutans.
    • Agglutinins include glycoproteins, mucins, fibronectin, α2-macroglobulin, and proline-rich proteins.
    • Myeloperoxidase and salivary peroxidase systems are bactericidal in the presence of thiocyanate/halide-H2O2.
    • Complement system (trace amounts) is likely derived from gingival crevicular fluid (GCF).
    • Leukocytes in saliva are primarily neutrophils, but a significant percentage may be incapable of phagocytosis.

    MALT in the Gastrointestinal Tract

    • MALT is specialized lymphoid tissue within the columnar, ciliated epithelial lining of the gut.
    • Goblet cells secrete mucus.
    • Paneth cells produce antimicrobial peptides (AMPs).
    • MALT exhibits an increased blood supply.
    • Tight junctions maintain the integrity of the epithelial barrier.

    Peyer's Patches & Mesenteric Lymph Nodes (MLNs)

    • Peyer's patches are specialized lymphoid tissues devoid of mucus production.
    • They sample antigens via M cells and dendritic cells (DCs).
    • Macrophages (MΦs) and regulatory T cells (Tregs) play a crucial role in regulation.

    Lamina Propria

    • The lamina propria is the site of T cell differentiation and IgA production.

    Microbiome and Tolerance

    • The gut microbiome plays a significant role in immune tolerance.

    Mucosa-associated lymphoid tissue (MALT) in the Oral Cavity

    • Oral MALT lacks goblet, Paneth, and M cells.
    • It comprises specialized lymphoid tissues, including Waldeyer's ring.
    • Oral lymphoid loci contain collections of lymphocytes and antigen-presenting cells (APCs) in the lamina propria, including Th1, Th2, and Th3 cells.

    Oral Langerhans Cells

    • Oral Langerhans cells are immature dendritic cells that express fewer activation molecules.
    • They constitutively endocytose and express high levels of co-stimulatory molecules, Fc receptors, and MHC I and II.
    • They express co-inhibitory molecules B7-H2 and B7-H3, which are upregulated in response to TLR4 activation, leading to IL-10 upregulation and suppression of excessive inflammation and autoimmune attacks.

    Th1 Cells

    • Th1 cells are activated by IL-12 and IL-18 signals.
    • They produce IFN-γ, stimulating macrophages to destroy intracellular bacteria and enhancing cytotoxic T cell activity.
    • They are effective against bacteria, viruses, and parasites.
    • They also produce IL-2.

    Th2 Cells

    • Th2 cells are activated by IL-4.
    • They target extracellular pathogens, parasites, and allergens.
    • They produce IL-4 and IL-13, leading to mast cell activation, B cell proliferation, Ig class switching, and increased MHC II expression.

    Th17 Cells

    • Th17 cells are activated by IL-6 and TGF-β.
    • They are involved in mucosal immunity against extra- and intracellular bacteria and fungi.
    • They produce IL-17A and IL-22, stimulating epithelial cells to produce IL-8 (recruiting neutrophils), increasing AMP production by macrophages and neutrophils, and inducing inflammation.

    Treg Cells

    • Treg cells are activated by TGF-β.
    • They produce IL-10, promoting immune suppression.
    • They inhibit macrophage activation, induce an M2 macrophage phenotype, suppress T helper cell differentiation, inhibit T and B cell proliferation, and suppress dendritic cell activation.

    Lymphocyte Homing

    • Lymphocyte homing is a process by which lymphocytes are guided to specific tissues and organs.
    • Activation signals (e.g., cytokines) released during infection or inflammation activate lymphocytes.
    • Lymphocytes express specific receptors that recognize chemokines released by target tissues.
    • This allows lymphocytes to sense and respond to specific signals that guide them to the appropriate location.

    Immune Mechanisms in Oral Health

    • Oral cavity is constantly exposed to a diverse range of microbes.
    • The immune system plays a crucial role in maintaining oral health by preventing infections and controlling inflammation.
    • Specialized immune cells, such as Langerhans cells and lymphocytes, patrol the oral mucosa and respond to microbial challenges.
    • AMPs and antibodies contribute to antibacterial and antiviral defense.
    • Immune dysregulation can lead to oral diseases, such as caries, periodontitis, and oral candidiasis.

    Epithelial Barrier Function and Antimicrobial Peptides

    • Oral epithelial cells produce antimicrobial peptides (AMPs) as a first line of defense against microbes
    • AMPs protect against bacterial, viral and fungal infections
    • Defensins (α-defensins and β-defensins) are effective against gram-positive and gram-negative bacteria
    • Cathelicidin (LL-37) has broad-spectrum antimicrobial activity and plays an important role in wound healing
    • Histatins are important for antifungal activity against Candida albicans
    • Secretory IgA is a major antibody in saliva and plays a critical role in preventing microbial adhesion and agglutination

    MALT in the Gastro-Intestinal Tract

    • The gastro-intestinal tract is lined with specialized cells that play important roles in defense
    • Goblet cells produce mucus, which traps and removes microbes
    • Paneth cells produce AMPs that directly kill microbes
    • Tight junctions between epithelial cells create a barrier against microbial penetration
    • Peyer's patches and mesenteric lymph nodes (MLNs) are lymphoid tissues in the gastro-intestinal tract that contribute to immune surveillance

    Peyer's Patches and MLNs

    • Peyer's patches and MLNs lack mucus producing cells and express M cells to take up antigens
    • M cells transport antigens to underlying dendritic cells which initiate the immune response
    • Macrophages and regulatory T cells (Treg) help to control the immune response in these tissues

    Lamina Propria

    • Lamina propria is a layer of connective tissue that supports the epithelial lining of the gut
    • It contains immune cells, including T cells, B cells, and macrophages
    • T cell differentiation and IgA production occurs in this layer

    Mucosa-associated lymphoid tissue (MALT)

    • MALT is a network of lymphoid tissues found throughout the body, including the oral cavity
    • Oral MALT is characterized by a collection of lymphocytes and antigen-presenting cells (APCs) in the lamina propria
    • Oral MALT plays a critical role in mounting both local and systemic immune responses

    Oral Langerhans Cells

    • Oral Langerhans cells (OLC) are specialized dendritic cells that are found in the oral mucosa
    • They are constitutively endocytotic and express high levels of co-stimulatory molecules, MHC I + II, Fc receptor, and co-inhibitory molecules B7-H2 + B7-H3
    • B7-H2 and B7-H3 signaling is up-regulated in response to TLR4 activation, leading to IL-10 up-regulation
    • OLC contribute to immune tolerance mechanisms by preventing excessive inflammation and autoimmune attacks

    Th1 Cells

    • Th1 cells are stimulated by IL-12 and IL-18
    • They are a key component of cellular immunity, providing defense against intracellular pathogens
    • Production of IFN-γ activates macrophages and cytotoxic T cells, targeting bacterial, viral, and parasitic infections
    • Th1 cells also produce IL-2, an essential cytokine for T-cell proliferation and differentiation

    Th2 Cells

    • Th2 cells are stimulated by IL-4
    • They are prominent in humoral immunity, targeting extracellular pathogens, parasites, and allergic reactions
    • Th2 cells produce IL-4 and IL-13, which promote mast cell activation, B cell proliferation, Ig class switching, and increased MHC II expression

    Th17 Cells

    • Th17 cells are stimulated by IL-6 and TGF-β
    • They are a key component of mucosal immunity, providing protection against extracellular and intracellular bacteria and fungi
    • Th17 cells produce IL-17A and IL-22, which stimulate epithelial cells to produce IL-8, leading to neutrophil recruitment and increased AMP production

    Treg Cells

    • Treg cells are stimulated by TGF-β
    • They express IL-10 and are key mediators of immune suppression
    • Treg cells contribute to maintaining immune tolerance by suppressing macrophage activation, promoting the M2 phenotype, inhibiting T helper cell differentiation, T and B cell proliferation and dendritic cell activation

    Lymphocyte Homing

    • Lymphocytes are guided to the site of infection or inflammation by signals, such as cytokines
    • Lymphocytes express tissue-specific receptors that help them recognize and respond to chemokines released by the tissues where they are needed.

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    Description

    Explore the vital role of antimicrobial peptides (AMPs) produced by epithelial cells, particularly focusing on their ability to combat various pathogens. This quiz covers the specific functions of AMPs in the oral cavity, including their antibacterial, antifungal, and immunomodulatory properties. Test your knowledge on this important aspect of innate immunity.

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