CONTENTSCONTENTS IntroductionIntroduction

ClassificationClassification SalivaSaliva Sulcular fluidSulcular fluid Epithelial keratinizationEpithelial keratinization Leukocytes in dentogingival areaLeukocytes in dentogingival area

INTRODUCTIONINTRODUCTION

The Immune system is essential for the The Immune system is essential for the maintenance of periodontal health and is central to maintenance of periodontal health and is central to the host response to periodontal pathogens. the host response to periodontal pathogens. However ,if the immune response is dysregulated, However ,if the immune response is dysregulated, inappropriate, persistent or excessive, then inappropriate, persistent or excessive, then damaging chronic inflammatory responses may damaging chronic inflammatory responses may result.result.

The oral cavity is loaded with aerobes and The oral cavity is loaded with aerobes and anaerobes which are normal commensals of the oral anaerobes which are normal commensals of the oral cavity. These commensal organism becomes cavity. These commensal organism becomes pathogenic if the host defense is compromised. pathogenic if the host defense is compromised. Hence an effective defense mechanism is necessary Hence an effective defense mechanism is necessary within the oral cavity to safeguard from these within the oral cavity to safeguard from these attacks.attacks.

Defense mechanisms of oral cavity can Defense mechanisms of oral cavity can be broadly classified into : be broadly classified into :

Saliva Saliva Sulcular fluid Sulcular fluid Epithelial keratinocytesEpithelial keratinocytes

MAJOR SALIVARY GLANDSMAJOR SALIVARY GLANDS

Basic functional unit of salivary gland are cluster Basic functional unit of salivary gland are cluster of cells called an acini.of cells called an acini.

Terminal secretory unitTerminal secretory unit

Composition Composition :: water-99% or morewater-99% or more

& 1% include:& 1% include: Antibacterial factorsAntibacterial factors Salivary antibodiesSalivary antibodies Enzymes Enzymes salivary buffers & coagulation factorssalivary buffers & coagulation factors

Antibacterial factorsAntibacterial factors saliva contains numeroussaliva contains numerous inorganic inorganic and and

organic factorsorganic factors that influence bacteria and their that influence bacteria and their products in the oral environment. products in the oral environment.

Inorganic factorsInorganic factors : : bicarbonatebicarbonate sodiumsodium potassiumpotassium phosphatesphosphates calciumcalcium fluoridesfluorides ammoniumammonium carbon dioxidecarbon dioxide

Organic components:Organic components:

lysozymeslysozymes

lactoferrinlactoferrin

myeloperoxidase myeloperoxidase

lactoperoxidaselactoperoxidase

agglutininsagglutinins ( glycoprotein, ( glycoprotein, mucins, Fibronectin)mucins, Fibronectin)

LysozymeLysozyme is a hydrolytic enzyme that cleaves the is a hydrolytic enzyme that cleaves the linkage between structural components of the linkage between structural components of the glycopeptides muramic acid- containing region of glycopeptides muramic acid- containing region of the cell wall of certain bacteria ,resulting in cell the cell wall of certain bacteria ,resulting in cell lysis.lysis.

Lysozyme works on both gram-negative and Lysozyme works on both gram-negative and gram positive organisms; its targets include gram positive organisms; its targets include Veilonella Veilonella species and species and Actinobacillus Actinobacillus actinomycetencomitans.actinomycetencomitans.

LACTOFERRINLACTOFERRIN

Lactoferrin links to free iron in the saliva causing bactericidal or bacteriostatic effects on various microorganisms requiring iron for their survival

Lactoferrin also provides fungicidal, antiviral, anti-inflammatory, and immunomodulatory functions

The The lactoperoxidase- thiocyanatelactoperoxidase- thiocyanate system system in saliva has been shown to be bactericidal in saliva has been shown to be bactericidal to some strains of to some strains of LactobacillusLactobacillus and and StreptococcusStreptococcus by preventing the by preventing the accumulation of lysine and glutamic acid, accumulation of lysine and glutamic acid, both of which are essential for bacterial both of which are essential for bacterial growth.growth.

Another finding is effective against Another finding is effective against ActinobacillusActinobacillus species. species.

MyeloperoxidaseMyeloperoxidase, an enzyme similar to , an enzyme similar to salivary peroxidase, is released by salivary peroxidase, is released by leukocytes and is bactericidal for leukocytes and is bactericidal for ActinobacillusActinobacillus but has added effect of but has added effect of inhibiting the attachment of inhibiting the attachment of ActinomycetesActinomycetes strains to hydroxyapatite .strains to hydroxyapatite .

Statherins inhibit the spontaneous precipitation of calcium phosphate salts and the growth of hydroxyapatite crystals on the tooth surface, preventing the formation of salivary and dental calculus.

The histatins, a family of histidine-rich peptides have antimicrobial activityantimicrobial activity against some strains of Streptococcus mutans and inhibit hemoagglutination of the periopathogen P. gingivallis.

Neutralize lipopolyscaccharides of G –ve bacteria.

Potent inhibitors of C. albicans.

SALIVARY ANTIBODIESSALIVARY ANTIBODIES Important group of defensive substance in saliva Important group of defensive substance in saliva

are Immunoglobulins.are Immunoglobulins. Salivary immunoglobulin is IgA.Salivary immunoglobulin is IgA. Small amount of IgM and IgG.Small amount of IgM and IgG.

IgA inhibits bacterial adherence. IgA inhibits bacterial adherence.

ENZYMESENZYMES The major enzyme is The major enzyme is parotid amylase.parotid amylase. Binds to bacteria promotes adhesion lead to either Binds to bacteria promotes adhesion lead to either

surface immune exclusion or adhesion of surface immune exclusion or adhesion of cariogenic or periodontopathogenic bacteria.cariogenic or periodontopathogenic bacteria.

Certain salivary enzymes have been reported in Certain salivary enzymes have been reported in increased concentrations in periodontal diseases.increased concentrations in periodontal diseases.

Proteolytic enzymes in the saliva are generated by Proteolytic enzymes in the saliva are generated by both the host and oral bacteria. These enzymes both the host and oral bacteria. These enzymes have been recognized as contributors to the have been recognized as contributors to the initiation and progression of periodontal disease.initiation and progression of periodontal disease.

To combat with these enzymes, saliva contains To combat with these enzymes, saliva contains antiproteases that inhibit cysteine proteases such antiproteases that inhibit cysteine proteases such as cathepsins and antileukoproteases that inhibit as cathepsins and antileukoproteases that inhibit elastase.elastase.

SALIVARY BUFFERS AND SALIVARY BUFFERS AND COAGULATION FACTORSCOAGULATION FACTORS

The maintenance of physiologic hydrogen ion The maintenance of physiologic hydrogen ion concentration (pH) at the mucosal epithelial cell concentration (pH) at the mucosal epithelial cell surface and the tooth surface is an important surface and the tooth surface is an important function of salivary buffers. function of salivary buffers.

In saliva the most important salivary buffer is the In saliva the most important salivary buffer is the bicarbonate-carbonic acid system.bicarbonate-carbonic acid system.

Saliva also contains Saliva also contains coagulation factorscoagulation factors (factors (factors VIII,IX and X; plasma thromboplastin antecedent VIII,IX and X; plasma thromboplastin antecedent [PTA]; Hageman factor)[PTA]; Hageman factor) that hasten blood that hasten blood coagulation and protect wounds from bacterial coagulation and protect wounds from bacterial invasion.invasion.

An active fibrinolytic enzyme may also be present.An active fibrinolytic enzyme may also be present.

LEUKOCYTESLEUKOCYTES

In addition to desquamated epithelial cells, the In addition to desquamated epithelial cells, the saliva contains all forms of leukocytes of which the saliva contains all forms of leukocytes of which the principal cells are principal cells are PMNsPMNs..

The number of PMNs varies from person to The number of PMNs varies from person to person at different times of the day and is increased person at different times of the day and is increased in gingivitis.in gingivitis.

PMNs reach the oral cavity by migrating PMNs reach the oral cavity by migrating through the lining of the gingival sulcus.through the lining of the gingival sulcus.

Living PMNs in saliva are sometimes called Living PMNs in saliva are sometimes called orogranulocytesorogranulocytes, and their rate of migration , and their rate of migration into the oral cavity is termed the into the oral cavity is termed the orogranulocytic migratory rate.orogranulocytic migratory rate.

2.SULCULAR FLUID2.SULCULAR FLUID

Sulcular fluid or gingival crevicular fluidSulcular fluid or gingival crevicular fluid (GCF) is serum exudate secreted by sulcular (GCF) is serum exudate secreted by sulcular epithelium in the gingival sulcus.epithelium in the gingival sulcus.

The presence of this fluid has been known The presence of this fluid has been known since the 19since the 19thth century, but its composition and century, but its composition and possible role in oral defense mechanism was possible role in oral defense mechanism was elucidated by the pioneering work ofelucidated by the pioneering work of Waerhaug Waerhaug and and Brill Brill and and KrasseKrasse in the 1950s. in the 1950s.

GENERATION OF GCFGENERATION OF GCF

COMPOSITION OF GCFCOMPOSITION OF GCF

Cellular elements Cellular elements ElectrolytesElectrolytes Organic compoundsOrganic compounds Metabolic and bacterial productsMetabolic and bacterial products Enzymes and enzyme inhibitorsEnzymes and enzyme inhibitors

Cellular elementsCellular elements• bacteriabacteria• desquamated epithelial cellsdesquamated epithelial cells• leukocytes leukocytes ( PMNs, lymphocytes, monocytes ( PMNs, lymphocytes, monocytes

/macrophages)/macrophages)

ElectrolytesElectrolytes • PotassiumPotassium• sodium sodium • calciumcalcium

ENZYMES &OTHER ENZYMES &OTHER COMPOUNDSCOMPOUNDS

Acid phosphataseAcid phosphatase Alkaline phosphataseAlkaline phosphatase ArylsulfataseArylsulfatase CytokinesCytokines EndopeptidasesEndopeptidases Chondroitin sulfataseChondroitin sulfatase CollagenaseCollagenase Plasminogen activatorPlasminogen activator cathelicidincathelicidin

ExopeptidasesExopeptidases FibrinFibrin FibronectinFibronectin GlycosidasesGlycosidases HyaluronidaseHyaluronidase ImmunoglobulinsImmunoglobulins Lactate dehydrogenaseLactate dehydrogenase Lactic acidLactic acid lysozymelysozyme

COMPOUNDS AND ENZYMES OF COMPOUNDS AND ENZYMES OF BACTERIAL ORIGINBACTERIAL ORIGIN

Acid phosphataseAcid phosphatase Alkaline phosphataseAlkaline phosphatase AminopeptidasesAminopeptidases Chondroitin sulfataseChondroitin sulfatase CollagenaseCollagenase DNaseDNase FibrinolysinFibrinolysin GlucosidasesGlucosidases

HemolysinHemolysin HyaluronidaseHyaluronidase IminopeptidasesIminopeptidases ImmunoglobulinaseImmunoglobulinase Phospholipase APhospholipase A Prostaglandin like productProstaglandin like product Trypsin like enzymeTrypsin like enzyme

METABOLIC & BACTERIAL PRODUCTSMETABOLIC & BACTERIAL PRODUCTS

Lactic acidLactic acid Hydroxy prolineHydroxy proline ProstaglandinsProstaglandins UreaUrea EndotoxinsEndotoxins Cytotoxic substancesCytotoxic substances Antibacterial factorsAntibacterial factors

CELLULAR & HUMORAL CELLULAR & HUMORAL ACTIVITY IN GCFACTIVITY IN GCF

Analysis of GCF has identified cell and humoral Analysis of GCF has identified cell and humoral responses in both healthy and those with responses in both healthy and those with periodontal diseasesperiodontal diseases

The cellular immune response include the The cellular immune response include the appearance of cytokinesappearance of cytokines in GCF, but there is no in GCF, but there is no clear evidence of a relationship between cytokines clear evidence of a relationship between cytokines and disease.and disease.

However, However, interleukin-1 alpha and IL-1 betainterleukin-1 alpha and IL-1 beta are are known to known to increaseincrease the binding of PMNs and the binding of PMNs and monocytes to endothelial cells, stimulate the monocytes to endothelial cells, stimulate the production of production of prostagladinEprostagladinE22 and release of and release of lysosomal enzymes & stimulate lysosomal enzymes & stimulate bone resorption.bone resorption.

Interferon alphaInterferon alpha present in GCF have a protective present in GCF have a protective role in periodontal disease because of its ability to role in periodontal disease because of its ability to inhibit bone resorption activity of inhibit bone resorption activity of IL-1 betaIL-1 beta..

CLINICAL SIGNIFICANCECLINICAL SIGNIFICANCE

GCF is an inflammatory exudateGCF is an inflammatory exudate.. The amount of GCF is greater when inflammation is The amount of GCF is greater when inflammation is

present.present. Factors which influence the amount of GCF are Factors which influence the amount of GCF are • Circadian periodicityCircadian periodicity• Sex hormonesSex hormones• mechanical stimulationmechanical stimulation• SmokingSmoking• Periodontal therapyPeriodontal therapy

DRUGS IN GCF:DRUGS IN GCF: TetracyclineTetracycline metronidazolemetronidazole

Tetracycline is effective in treating Tetracycline is effective in treating periodontal diseases becauseperiodontal diseases because

1.1. Their concentration in GCF is 2-10 times Their concentration in GCF is 2-10 times more than blood serummore than blood serum

2.2. Inhibit the growth of Actinobacillus Inhibit the growth of Actinobacillus actinomycetemcomitansactinomycetemcomitans

3.3. Have anti Collagenase effect inhibiting Have anti Collagenase effect inhibiting tissue destruction.tissue destruction.

3.LEUKOCYTES IN THE 3.LEUKOCYTES IN THE DENTOGINGIVAL AREADENTOGINGIVAL AREA

Found in healthy gingival sulcusFound in healthy gingival sulcus

Leukocytes found are predominantly Leukocytes found are predominantly PMNs.PMNs.

They appear in small number extravascularly in the They appear in small number extravascularly in the connective tissue adjacent to the bottom of the connective tissue adjacent to the bottom of the sulcus; from there, they travel across the sulcus; from there, they travel across the epithelium to the gingival sulcus, where they are epithelium to the gingival sulcus, where they are expelledexpelled

Differential counts of leukocytes from clinically Differential counts of leukocytes from clinically healthy gingival sulci have shown 91.2-91.5% PMNs healthy gingival sulci have shown 91.2-91.5% PMNs and 8.5-8.8% mononuclear cells.and 8.5-8.8% mononuclear cells.

Mononuclear cells were identified as 58% B Mononuclear cells were identified as 58% B lymphocytes, 24% T lymphocytes & 18% lymphocytes, 24% T lymphocytes & 18% mononuclear phagocytes.mononuclear phagocytes.

The ratio of T lymphocytes to B lymphocytes was The ratio of T lymphocytes to B lymphocytes was found to be reversed from normal ratiofound to be reversed from normal ratio

1:3 in GCF1:3 in GCF

Leukocytes are attracted by different plaque bacteria Leukocytes are attracted by different plaque bacteria but can also be found in the dentogingival region of but can also be found in the dentogingival region of germ free adult animals.germ free adult animals.

Leukocytes were reported in the gingival sulcus in non Leukocytes were reported in the gingival sulcus in non mechanically irritated healthy gingiva, indicated that mechanically irritated healthy gingiva, indicated that their migration may be independent of an their migration may be independent of an increase in increase in vascular permeability.vascular permeability.

The majority of these cells are viable and have The majority of these cells are viable and have phagocytic and killing capacityphagocytic and killing capacity..

These leukocytes constitute a major protective These leukocytes constitute a major protective mechanism against the extension of plaque into mechanism against the extension of plaque into gingival sulcus.gingival sulcus.

The main port of entry of leukocytes into the oral The main port of entry of leukocytes into the oral cavity is the gingival sulcus.cavity is the gingival sulcus.

4.EPITHELIAL CELLS4.EPITHELIAL CELLS

Epithelial cells plays an active role in innate host Epithelial cells plays an active role in innate host defense by responding to bacteria which means the defense by responding to bacteria which means the epithelium participates actively in responding to epithelium participates actively in responding to infection, in signaling further host reactions and infection, in signaling further host reactions and integrating innate and acquired immune responses.integrating innate and acquired immune responses.

The role of oral epithelium in defense by its The role of oral epithelium in defense by its degree of keratinizationdegree of keratinization and and turnover rate.turnover rate.

The gingival epithelium consists of a continuous The gingival epithelium consists of a continuous lining of lining of stratified squamous epitheliumstratified squamous epithelium ,and ,and the three different morphologic and functional the three different morphologic and functional points of view; the oral or outer epithelium points of view; the oral or outer epithelium ,sulcular epithelium and junctional epithelium.,sulcular epithelium and junctional epithelium.

The principal cell type of gingival epithelium is The principal cell type of gingival epithelium is the the keratinocytekeratinocyte . Other cells found in the . Other cells found in the epithelium are the clear cells or nonkeratinocytes, epithelium are the clear cells or nonkeratinocytes, which include the which include the langerhans cells, merkel cells, langerhans cells, merkel cells, and melanocytes.and melanocytes.

Main function of gingival epithelium is to protect Main function of gingival epithelium is to protect the deep structures, while allowing a selective the deep structures, while allowing a selective interchange with the oral environment.interchange with the oral environment.

This is achieved by This is achieved by proliferation proliferation and and differentiationdifferentiation of the keratinocytes. of the keratinocytes.

Differentiation of keratinocyte by keratinization Differentiation of keratinocyte by keratinization process which leads to production of an ortho process which leads to production of an ortho keratinized superficial horny layer which is made up keratinized superficial horny layer which is made up of mainly keratin protein.of mainly keratin protein.

This layer makes intact barrier between the oral This layer makes intact barrier between the oral environment and deep layers.environment and deep layers.

Langerhans cellsLangerhans cells located among the located among the keratinocytes at supra basal levels belong to the keratinocytes at supra basal levels belong to the mononuclear phagocyte system as modified mononuclear phagocyte system as modified monocytes.monocytes.

They have an important role in the immune They have an important role in the immune reaction as reaction as antigen presenting cells for antigen presenting cells for lymphocyteslymphocytes

Epithelial cells stimulated with bacterial components Epithelial cells stimulated with bacterial components and cytokines directly produce and cytokines directly produce MMPsMMPs, which , which contribute to loss of connective tissue.contribute to loss of connective tissue.

Epithelial cells also secrete a range of cytokines in Epithelial cells also secrete a range of cytokines in response to periodontal bacteria (response to periodontal bacteria (P.gingivalis, P.gingivalis, A.actinomycetemcomitans, F.nucleatum, P.intermediaA.actinomycetemcomitans, F.nucleatum, P.intermedia), ), which which signal immune responses.signal immune responses.

cytokines IL-1beta, TNF-alpha & IL-6 ,which serve to cytokines IL-1beta, TNF-alpha & IL-6 ,which serve to signal neutrophils and monocytes migration from the signal neutrophils and monocytes migration from the vasculature into periodontal tissues.vasculature into periodontal tissues.

CONCLUSIONCONCLUSION

. . The examination of innate host responses in clinically The examination of innate host responses in clinically healthy people has revealed a low-level 'inflammatory healthy people has revealed a low-level 'inflammatory surveillance' state, in which the host maintains an surveillance' state, in which the host maintains an effective barrier against bacterial infection. effective barrier against bacterial infection. Normal Normal oral micro flora may not only form a series of oral micro flora may not only form a series of nonpathogenic commensal communities, but may nonpathogenic commensal communities, but may also participate in establishing this protective also participate in establishing this protective statestate, thus functioning as symbiotic partners with the , thus functioning as symbiotic partners with the host. Mechanisms of bacterial recognition that should host. Mechanisms of bacterial recognition that should help to explain how members of the micro biota help to explain how members of the micro biota maintain an effective host-defense barrier are maintain an effective host-defense barrier are emerging. Also, studies of the host activation potential emerging. Also, studies of the host activation potential of periodontal pathogens suggest that dysfunctional of periodontal pathogens suggest that dysfunctional host responses may contribute to pathogenesis. . host responses may contribute to pathogenesis. .

REFERENCESREFERENCES

CARRANZA’S CLINICAL PERIODONTOLOGYCARRANZA’S CLINICAL PERIODONTOLOGY

ORBAN’S ORAL HISTOLOGY &EMBRYOLOGYORBAN’S ORAL HISTOLOGY &EMBRYOLOGY