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Questions and Answers
What is the primary function of mucosa-associated lymphoid tissue (MALT) in the gastrointestinal tract?
What is the primary function of mucosa-associated lymphoid tissue (MALT) in the gastrointestinal tract?
Which antimicrobial agent in saliva is known for inhibiting P. gingivalis?
Which antimicrobial agent in saliva is known for inhibiting P. gingivalis?
What type of immune defense do defensins contribute to in saliva?
What type of immune defense do defensins contribute to in saliva?
Which agent in saliva is a Fe^3+^ chelator that inhibits the metabolic activity of microorganisms?
Which agent in saliva is a Fe^3+^ chelator that inhibits the metabolic activity of microorganisms?
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Which component of saliva has bactericidal activity in the presence of thiocyanate and hydrogen peroxide?
Which component of saliva has bactericidal activity in the presence of thiocyanate and hydrogen peroxide?
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What role does secretory IgA play in the immune defenses of saliva?
What role does secretory IgA play in the immune defenses of saliva?
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Which of the following antimicrobial agents is specifically effective against Candida albicans?
Which of the following antimicrobial agents is specifically effective against Candida albicans?
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How do neutrophils in saliva typically contribute to immune defense?
How do neutrophils in saliva typically contribute to immune defense?
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What role does the lamina propria play in mucosal immunity?
What role does the lamina propria play in mucosal immunity?
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Which of the following best describes the function of defensins in saliva?
Which of the following best describes the function of defensins in saliva?
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What is the mechanism of action of lysozyme in saliva?
What is the mechanism of action of lysozyme in saliva?
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Which antimicrobial agent in saliva targets chitin in fungal pathogens?
Which antimicrobial agent in saliva targets chitin in fungal pathogens?
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Which statement about the myeloperoxidase system in saliva is accurate?
Which statement about the myeloperoxidase system in saliva is accurate?
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Which component of saliva is responsible for agglutinating bacteria?
Which component of saliva is responsible for agglutinating bacteria?
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What distinguishes the role of secretory immunoglobulin A (s-IgA) in saliva?
What distinguishes the role of secretory immunoglobulin A (s-IgA) in saliva?
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Which of the following is a characteristic feature of α-amylase's function in saliva?
Which of the following is a characteristic feature of α-amylase's function in saliva?
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Study Notes
Mucosal Associated Lymphoid Tissue (MALT)
- MALT acts as a barrier to infection
MALT in the Gastrointestinal Tract
- Specialized cells in the columnar, ciliated epithelial lining of the gastrointestinal tract include:
- M cells (microfold cells)
- Goblet cells
- Paneth cells
- Enteroendocrine cells
- Peyer’s patches and mesenteric lymph nodes (MLNs) are important components of the gut-associated lymphoid tissue (GALT)
- Peyer's patches are located in the ileum
- MLNs receive lymph draining from Peyer's patches and other parts of the gut
- The lamina propria is the connective tissue layer beneath the epithelial lining
- It contains immune cells such as lymphocytes, macrophages and plasma cells
Oral Cavity Immune Defenses
- The oral cavity is constantly exposed to a diverse range of microorganisms
- Saliva is the primary defense mechanism
Soluble Defenses in Saliva
- Saliva exhibits antimicrobial properties through various agents:
- α-Amylase inhibits P. gingivalis
- Defensins (α & β), cationic peptides, exert antibacterial, antiviral and immunomodulatory actions
- Cystatins and secretory leukocyte protease inhibitor inhibit microbial protease activity
- Histatins 1, 3, and 5 inhibit Candida albicans
- Chitinase possesses antifungal properties, causing cell wall lysis
- Statherin inhibits anaerobic bacterial growth
- Secretory IgA (s-IgA) and other immunoglobulins (s-IgG, s-IgM) contribute to:
- Inhibition of bacterial adhesion
- Bacterial agglutination
- Virus neutralization
- s-IgA is the predominant antibody in saliva
- Lactoferrin chelates Fe^3+^ ions, hindering microbial metabolic activity
- Lysozyme degrades bacterial cell walls by hydrolyzing glycosidic bonds, targeting S. mutans
- Agglutinins, including glycoproteins, mucins, fibronectin, 2-macroglobulin, and proline-rich proteins, bind and clump bacteria
- The myeloperoxidase system (enzyme, thiocyanate/halide-H
2O2) exhibits bactericidal activity - Salivary peroxidase system (enzyme, thiocyanate/halide-H
2O2) aids in pathogen elimination - Complement (present in trace amounts) is largely derived from gingival crevicular fluid (GCF)
- Leukocytes in saliva are primarily neutrophils, with up to 50% potentially lacking phagocytic capabilities
Mucosa Associated Lymphoid Tissue (MALT)
- A critical component of the immune system, found in mucosal tissues throughout the body
- Plays a crucial role in defending against infections
MALT in the Gastrointestinal Tract
- Specialised cells within the columnar, ciliated epithelial lining of the gastrointestinal tract (GI tract)
- Goblet cells produce mucus that acts as a physical barrier, trapping pathogens and preventing them from adhering to the epithelial surface.
- Enterocytes form the epithelial lining, creating a tight barrier to prevent pathogen entry
- M cells are specialized antigen-presenting cells that actively sample luminal contents and transport antigens to underlying immune cells.
- Paneth cells secrete antimicrobial peptides, such as defensins, that contribute to the innate immune response
- Peyer’s Patches are secondary lymphoid organs in the small intestine that are critical for initiating immune responses against ingested pathogens:
- Large aggregates of lymphocytes that can trap antigens and initiate an immune response
- Contain specialized cells called M cells that transport antigens from the lumen to underlying lymphocytes.
- Mesenteric Lymph Nodes (MLNs) are located near the Peyer's patches:
- Lymphatic vessels draining the gut connect to the MLNs.
- MLNs receive antigens from the gut and are a major site of immune response activation.
- Lamina Propria is the connective tissue layer underlying the epithelial lining
- Contains a variety of immune cells, including macrophages, neutrophils, and lymphocytes, that contribute to immune responses and prevent infection.
Oral Cavity Immune Defenses
- Specialized immune defenses protect the oral cavity from infection.
- Saliva plays a crucial role in maintaining immune homeostasis:
- Contains a variety of antimicrobial agents that inhibit microbial growth and activity
- Secretory IgA (sIgA) is the major antibody in saliva, plays a key role in defense by neutralising pathogens, agglutinating bacteria, and inhibiting their adherence to mucosal surfaces.
Soluble Defenses in Saliva
- Saliva contains several antimicrobial agents that contribute to the protection of the oral cavity:
- α-Amylase inhibits the growth of P. gingivalis
- Defensins (α&β) possess antimicrobial, antiviral, and immunomodulatory properties
- Cystatins and Secretory Leukocyte Protease Inhibitor (SLPI) inhibit microbial proteases, limiting their ability to degrade proteins.
- Histatins (1, 3 & 5) inhibit the growth of Candida albicans
- Chitinase has antifungal properties and can lyse fungal cell walls
- Statherin inhibits anaerobic bacterial growth.
- Lactoferrin chelates iron (Fe^3+^) ions, hindering metabolic activity of microorganisms
- Lysozyme hydrolyzes glycosidic bonds in bacterial cell walls, disrupting their structure and killing them.
- S.mutans is particularly susceptible to lysozyme.
- Agglutinins, including glycoproteins, mucins, fibronectin, and 2-macroglobulin, bind to and agglutinate bacteria aiding in their removal.
- Myeloperoxidase system, in combination with thiocyanate/halide-H
2O2, exhibits bactericidal activity. - Salivary peroxidase system, utilizing enzyme thiocyanate/halide-H
2O2, contributes to microbial inactivation - Complement (present in trace amounts) is mainly derived from gingival crevicular fluid (GCF). C3 is a key component of the complement cascade
- Leukocytes in saliva are primarily neutrophils, although a significant portion may lack phagocytic ability.
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Description
This quiz explores the role of Mucosal Associated Lymphoid Tissue (MALT) in the immune defense of the gastrointestinal tract and oral cavity. It covers specialized cells, Peyer's patches, mesenteric lymph nodes, and the protective functions of saliva against microorganisms. Test your knowledge on how these components work together to guard the body against infections.
