Defence Mechanism of Gingiva in Periodontal Immunology

Defence Mechanism of Gingiva

• The gingival tissue is constantly subjected to mechanical and bacterial aggressions.
• Resistance to these actions is provided by saliva, GCF, and epithelium.
• The role of epithelium in defence depends on keratinization and turn over rate.
• The principal cell is keratinocyte, which protects the deep structures and allows selective interchange with the oral environment.

Epithelial Defence Mechanism

• The main function of the epithelium is to protect the deep structures and allow selective interchange with the oral environment.
• This is achieved by proliferation and differentiation of keratinocytes.
• Other proteins, keratinin and involucrin, form a chemically resistant structure.
• The uppermost cells of the stratum spinosum contain dense granules known as keratinosomes or odland bodies.
• These granules contain a large amount of acid phosphatase, which is related to the degree of keratinization.

Langerhans Cells

• Langerhans cells are also present in the epithelium and are known as antigen-presenting cells.
• They play an important role in immune reaction for lymphocytes.

Gingival Crevicular Fluid (GCF)

• GCF is secreted by the sulcular epithelium and is an inflammatory exudate.
• Methods of collection include twisted threads, absorbing paper strips, micropipettes, and intracrevicular washings.
• The amount of fluid collected by paper strip is measured by staining and using a magnifying glass or electronic method.

Composition of GCF

• GCF contains cellular elements, electrolytes, organic compounds, metabolic and bacterial products.
• Cellular elements include epithelial cells, leukocytes, and bacteria, such as P. gingivalis, A. viscosus, and C. rectus.
• Electrolytes include Na, Ca, K, and P.
• Organic compounds include glucose, hexosamine, hexuronic acid, proteins, phosphorous, and lipids.
• Metabolic and bacterial products include lactic acid, hydroxyproline, prostaglandins, endotoxins, and cytotoxic substances.

Antibacterial Factors in GCF

• Acid phosphatase is the main source of AP in the crevicular area and is confined to the azurophil granules of PMNs.
• AP is bacteriocidal and is also found in bacteria in the sulcus, such as Aa and Capnocytophaga.
• Alkaline phosphatase is correlated with pocket depth and is present in PMNs and gram-negative bacteria.
• Beta glucoronidase is found in the azurophilic or primary granules of PMNs and is also found in plaque bacteria.
• Lysozyme is found in PMNs and contributes to pocket formation.

Enzymes in GCF

• Hyaluronidase is an enzyme that degrades hyaluronic acid.
• Proteolytic enzymes include cathepsin D, cathepsin G, elastase, collagenase, and plasminogen activators.

Cellular and Humoral Activity in GCF

• The cellular immune response includes the appearance of cytokines, such as IL-1alpha and 1beta.
• IL-1 is responsible for pocket formation and is known as the lethal cytokine.

Factors Affecting GCF

• Circadian periodicity: gradual increase in GCF from 6AM to 10PM and thereafter it decreases.
• Sex hormones: female sex hormones increase GCF flow.
• Gingival crevicular fluid: increased GCF flow is a sign of inflammation.
• Physiologic processes: chewing, mastication increases the flow of GCF.
• Periodontal therapy: GCF flow increases during the healing period.
• Smoking: smoking increases GCF flow.

Role of Saliva

• Salivary secretion is protective in nature and maintains the oral epithelium in a physiologic state.
• It exerts influence by mechanically cleaning exposed surfaces and buffering acids produced by bacteria.
• Mastication increases saliva during physiologic processes.