Phagocyte function in juvenile periodontitis

Short-term exposure to oleandrin enhances responses to IL-8 by increasing cell surface IL-8 receptors

BACKGROUND AND PURPOSE

One of the first steps in host defence is the migration of leukocytes. IL-8 and its receptors are a chemokine system essential to such migration. Up-regulation of these receptors would be a viable strategy to treat dysfunctional host defence. Here, we studied the effects of the plant glycoside oleandrin on responses to IL-8 in a human monocytic cell line.

EXPERIMENTAL APPROACH

U937 cells were incubated with oleandrin (1-200 ng mL(-1) ) for either 1 h (pulse) or for 24 h (non-pulse). Apoptosis; activation of NF-κB, AP-1 and NFAT; calcineurin activity and IL-8 receptors (CXCR1 and CXCR2) were measured using Western blotting, RT-PCR and reporter gene assays.

KEY RESULTS

Pulse exposure to oleandrin did not induce apoptosis or cytoxicity as observed after non-pulse exposure. Pulse exposure enhanced activation of NF-κB induced by IL-8 but not that induced by TNF-α, IL-1, EGF or LPS. Exposure to other apoptosis-inducing compounds (azadirachtin, resveratrol, thiadiazolidine, or benzofuran) did not enhance activation of NF-κB. Pulse exposure to oleandrin increased expression of IL-8 receptors and chemotaxis, release of enzymes and activation of NF-κB, NFAT and AP-1 along with increased IL-8-mediated calcineurin activation, and wound healing. Pulse exposure increased numbers of cell surface IL-8 receptors.

CONCLUSIONS AND IMPLICATIONS

Short-term (1 h; pulse) exposure to a toxic glycoside oleandrin, enhanced biological responses to IL-8 in monocytic cells, without cytoxicity. Pulse exposure to oleandrin could provide a viable therapy for those conditions where leukocyte migration is defective.

Study of neutrophils isolated from peripheral blood of patients suffering from aggressive periodontitis at the cellular level: Receptors and cytoskeletal reorganization

BACKGROUND

Aggressive periodontitis (AgP) has been associated with polymorphonuclear leukocyte's (PMNL) dysfunction and periodontal pathogens possess variety of virulence factors that can impair PMNL's function. This study investigated the possible association between defective neutrophil adhesion and β(2) -integrin expression and defective neutrophil migration and actin polymerization level in the peripheral blood of neutrophils from the patients with AgP.

MATERIALS AND METHODS

A total of 30 individuals both male and female, age ranges between 13 - 48 years, were included in the study. Healthy controls (group I, n=10), chronic periodontitis (ChP) (group II, n=10), and AgP (group III, n=10), all without any systemic diseases and non-smokers, were recruited. Peripheral blood samples were taken and β(2) -integrin expression and actin polymerization levels were estimated by using fluorescence activated cell sorter analysis.

RESULTS

In AgP cases, both average values (β(2) -integrin and actin level) were significantly less than that of normal subjects (<0.001). But for ChP cases, only the average value of actin level is significantly lower than that of normal subjects (<0.025).

CONCLUSION

Lower β(2) -integrin expression in the AgP cases signifies lower neutrophil adhesion in AgP cases than normal, and the lower average value of actin polymerization for the AgP cases suggest lower migration capacity of neutrophils in AgP cases than normal.

Rosiglitazone reduces the evolution of experimental periodontitis in the rat

The peroxisome proliferator-activated receptor-gamma (PPAR-gamma) receptor appears to play a pivotal role in the regulation of cellular proliferation and inflammation. Recent evidence also suggests that rosiglitazone, a PPAR-gamma agonist, reduces acute and chronic inflammation. We hypothesized that rosiglitazone would attenuate periodontal inflammation. In the present study, we investigated the effects of rosiglitazone in a rat model of ligature-induced periodontitis. At day 8, ligation significantly induced an increase in neutrophil infiltration, as well as of gingivomucosal tissue expression of iNOS, nitrotyrosine formation, and poly (ADP-ribose) polymerase activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone destruction. Intraperitoneal injection of rosiglitazone (10 mg/kg 10% DMSO daily for 8 days) significantly decreased all of the parameters of inflammation, as described above. Analysis of these data demonstrated that rosiglitazone exerted an anti-inflammatory role during experimental periodontitis, and was able to ameliorate the tissue damage associated with ligature-induced periodontitis.

Pyrrolidine dithiocarbamate reduced experimental periodontitis

Nuclear factor-kappaB (NF-kappaB) is a transcription factor which plays a pivotal role in the induction of genes involved in physiological processes as well as in the response to injury and inflammation. Dithiocarbamates are antioxidants which are potent inhibitors of NF-kappaB. We postulated that pyrrolidine dithiocarbamate (PDTC) would attenuate inflammation. In the present study, we have investigated the effects of PDTC, in a rat model of periodontitis. Periodontitis was induced in rats by placing around the lower left first molar a 2/0 braided silk. At day eight the gingivomucosal tissue encircling the mandibular first molar was removed for biochemical and histological analysis. At day eight ligations significantly induced an increase neutrophil infiltration as well as the gingivomucosal tissue expression of TNF-alpha and iNOS as well as nitrotyrosine formation and poly (ADP-ribose) polymerase activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone destruction. Intraperitonial injection of PDTC (10 mg/kg daily for eight days) significantly reduced all of the parameters of inflammation as described above. These data demonstrate that PDTC exerts an anti-inflammatory role during experimental periodontitis and is able to ameliorate the tissue damage associated with ligature-induced periodontitis.

Resistance of fluorescent-labelled Actinobacillus actinomycetemcomitans strains to phagocytosis and killing by human neutrophils

Neutrophils are initially the predominant cells involved in the host defence of bacterial infections, including periodontal disease. Aggressive periodontitis is associated with Actinobacillus actinomycetemcomitans, a Gram-negative capnophilic microorganism. Infections caused by A. actinomycetemcomitans are not resolved by the host immune response despite the accumulation of neutrophils at the site of inflammation. To better understand the role of natural host defence mechanisms in A. actinomycetemcomitans infections, the interaction of phenotypically diverse strains of this pathogen with human neutrophils was assessed directly using techniques such as genetic labelling with the gene for green fluorescent protein, fluorescence-activated cell sorting and fluorescence imaging. The study included clinical isolates of A. actinomycetemcomitans represented by self-aggregating, biofilm-associated and isogenic planktonic variants. Data obtained showed that complement-mediated phagocytosis of A. actinomycetemcomitans was generally inefficient regardless of strain-specific serotype or leukotoxin production. Furthermore, the majority of ingested bacteria remained viable after exposure to neutrophils for 1 h. Interestingly, uptake of antibody-opsonized bacteria resulted in the rapid cell death of neutrophils. This was in contrast to ingestion of complement-opsonized bacteria, which did not affect neutrophil viability. The methods used in this study provided reliable and reproducible results with respect to adherence, phagocytosis and killing of A. actinomycetemcomitans when encountering human neutrophils.

Effects of Tempol, a membrane-permeable radical scavenger, in a rodent model periodontitis

BACKGROUND

Recent studies have demonstrated that Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl), a cell membrane-permeable radical scavenger, exerts protective effects in various models of inflammation and shock. Reactive oxygen species (ROS) plays a pivotal role in the induction of genes involved in physiological processes as well as in the response to inflammation.

AIM

We have investigated the effect of Tempol in a rat model of periodontitis.

MATERIALS AND METHODS

Periodontitis was induced in rats by placing a 2/0 braided silk ligature around the lower left first molar. At day 8, the gingivomucosal tissue encircling the mandibular first molar was removed for evaluation of neutrophils infiltration, tissue permeability, nitrotyrosine formation, poly-(ADP-ribose) polymerase (PARP) activation, radiography and histology.

RESULTS AND CONCLUSIONS

Legation significantly induced an increased neutrophil infiltration and a positive staining for nitrotyrosine formation and PARP activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone erosion as evaluated by radiography analysis. Intraperitonial injection of Tempol (10 mg/kg daily for 8 days) significantly decreased all of the parameters of inflammation as described above. This suggests that antioxidant therapies, which interfere with ROS, may be of benefit in the treatment of periodontitis.

Reduced development of experimental periodontitis by treatment with M40403, a superoxide dismutase mimetic

M40403, [manganese(II)dichloro[(4R,9R,14R,19R)-3,10,13,20,26 pentaazatetracyclo[20.3.1.0.(4,9)0(14,19)]hexacosa-1(26),-22(23),24-triene]], is a low-molecular-weight, synthetic, manganese-containing superoxide dismutase mimetic that removes superoxide anions without interfering with other reactive species known to be involved in inflammatory responses (e.g., nitric oxide, NO and peroxynitrite, ONOO-). As such, M40403 represents an important pharmacological tool to dissect the roles of superoxide anion in acute and chronic inflammation. For this purpose, the pharmacological profile of M40403 was evaluated in a rat model of periodontitis. Periodontitis was induced in rats by placing a 2/0 braided silk around the lower left first molar. On day 8 the gingivomucosal tissue encircling the first molar was removed for biochemical and histological analysis. Ligation significantly increased inducible nitric oxide synthase activity and expression, and gingival tissue revealed increased neutrophil infiltration, lipid peroxidation and positive staining for nitrotyrosine formation and poly (ADP-ribose) polymerase activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone destruction. Intraperitoneal injection of M40403 (10 mg/kg daily for 8 days) significantly decreased all of the above-described markers of inflammation. This suggests compounds that inhibit the generation of superoxide anion, such as M40403 may be potentially useful for the treatment of periodontitis.

Altered chemotactic behavior of crevicular PMNs in different forms of periodontitis

BACKGROUND, AIMS

Polymorphonuclear neutrophils (PMN) are the predominant host defence cells in the gingival sulcus. Previous work demonstrates that the in vitro phagocytosis of crevicular cells in localised early onset periodontitis (LEOP) and generalised early onset periodontitis (GEOP) lesions is diminished. The present study extends this work by characterizing the chemotaxis function of crevicular fluid (CF) PMNs in various forms of periodontitis.

METHODS

We investigated 7 patients with LEOP, 11 patients with GEOP, 12 patients with adult periodontitis (AP) and 2 age- and sex-matched healthy control groups. The two deepest sites of each quadrant in test and control subjects were selected for crevicular sampling. Chemotaxis was performed in a micro chamber (moist atmosphere, 5% CO2, 37 degrees C, 30 min) using N-formyl-methionyl-leucyl-phenylalanine (FMLP, 1 x 10(-7) mol FMLP/l) as a chemoattractant. The total chemotaxis was defined as the difference between the number of cells migrating towards FMLP minus the number of cells migrating towards PBS, counted in 20 randomly selected fields. Membranes were examined microscopically at 400 x magnification.

RESULTS

The chemotactic activity in the adult periodontitis group was significantly higher compared to the age-related control group. However, we found a statistically significant reduction of chemotactic activity in LEOP and GEOP patients compared to the controls.

CONCLUSIONS

These results indicate an increase of chemotactic activity from CF-PMN in patients with adult periodontitis, but on the other hand, a significant reduction of chemotactic responsiveness of these cells in LEOP and GEOP lesions.

Cytoskeletal actin reorganization in neutrophils from patients with localized juvenile periodontitis

Localized juvenile periodontitis (LJP) is an early-onset periodontal disease associated with a polymorphonuclear neutrophil (PMN) defective migratory response. Kinetics of actin polymerization-depolymerization determine the shape changes occurring in the plasma membrane-associated cytoskeleton and provide the driving force for directed cell migration (chemotaxis). Therefore, we investigated the relation between an abnormality in LJP PMN chemotaxis and an altered reorganization of the actin filament network. PMNs isolated from peripheral blood of LJP patients (n=14) and matching control subjects (n=12) were evaluated for random and directed migration in a Boyden chamber assay, and the kinetics of actin polymerization were studied by flow cytometry. Three groups of LJP patients could be distinguished on the basis of their PMN-chemotactic response compared to their matched control: depressed (n=6), normal (n=4), and elevated (n=4). The abnormal (depressed or elevated) chemotaxis was generally not related to abnormal random migratory response, except for two patients. Since the kinetics of formyl-methionyl-leucyl-phenylalanine-induced F-actin response were highly variable from one subject to another, means were calculated at each timepoint with the values obtained from each group of subjects and compared by a general factorial design analysis. No statistically significant differences were detected between the control group and the LJP patient group. Furthermore, the data did not show a correlation between the kinetics of actin polymerization-depolymerization and the abnormal chemotactic response observed in LJP PMNs. Hence, the chemotaxis defect in LJP PMN appears to be mediated by signaling events that carry their effect independently of an intact cytoskeleton.

Peroxidases, lactoferrin and lysozyme in peripheral blood neutrophils, gingival crevicular fluid and whole saliva of patients with localized juvenile periodontitis

OBJECTIVE

The aim of this study was to examine the longitudinal association of selected non-immune anti-microbial host factors (peroxidases, lysozyme and lactoferrin) to the localized juvenile periodontitis (LJP) disease status.

MATERIALS AND METHODS

Peroxidases, lysozyme and lactoferrin were quantitated from seven patients with LJP before and after periodontal therapy. Analyses were performed from simultaneously collected samples of peripheral blood polymorphonuclear leukocytes (PMNs), gingival crevicular fluid (GCF from diseased sites) and paraffin-stimulated whole saliva. Similar assays were done also from seven periodontally healthy controls.

RESULTS

During untreated phase of LJP myeloperoxidase, lysozyme and lactoferrin concentrations were remarkably elevated in peripheral blood PMNs, also reflected in their high concentrations in GCF. All these values normalised with respect to healthy controls during the periodontal therapy. No similar longitudinal changes were seen in whole saliva but during therapy salivary peroxidase concentrations declined below the control values, in accordance with our previous observations in parotid saliva samples of LJP patients.

CONCLUSIONS

In LJP the concentrations of lysozyme, lactoferrin and myeloperoxidase are significantly elevated in peripheral blood PMNs, also reflected in GCF. During periodontal therapy these values decline and approach those observed in healthy controls. No similar changes are seen in stimulated whole saliva.

Chemiluminescence responses and chemotaxis of monocytes from patients with early rheumatoid arthritis

We studied chemiluminescence (CL) responses and chemotaxis of monocytes of patients with early rheumatoid arthritis (RA) before starting anti-rheumatic drug treatment and correlated the data to 2-year prognosis of the patients. Luminol-enhanced CL responses of RA monocytes to N-formylmethionyl-leucyl-phenylalanine or to phorbol myristate acetate, and lucigenin-enhanced responses to opsonized zymosan particles were significantly higher than those of healthy control subjects. Distances of chemotactic, chemokinetic and random migration of RA monocytes were similar to those of control cells. High CL responsiveness correlated with seropositivity but not with presence of HLA-DR4 or that of erosions at 2-year follow-up. The results give credence to the view that monocytes are metabolically activated in early untreated RA, but increased respiratory burst activity does not predict early development of erosions.

Periodontal and systemic findings in children with marginal bone loss in the primary dentition

In a previous population-based study of 3896 7-9-year-old children living in Sweden, it was found that 32 children (0.8%) exhibited radiographic, periodontal bone loss at > or = 2 proximal surfaces of their deciduous teeth. In the present study, 26 of the 32 children were subjected to additional oral and systemic health examination. 20 other children without any radiographic evidence of bone loss in their primary dentition served as referents. None of the cases or the referents were detected to have any systemic disease. The frequency of bleeding and suppuration on probing, radiographic proximal calculus and probing attachment loss was higher among the cases than the referents. Actinobacillus actinomycetemcomitants was found subgingivally in 14 of the cases but in none of the referents. 11 of 22 cases analysed for presence of serum antibodies against A. actinomycetemcomitans leukotoxin were sero-positive compared to none of 7 referents available for analysis. Evaluation of the data from each child revealed wide variations in clinical parameters among the children in the case group. In this group, there were children with deep probing depths, probing attachment loss, suppuration on probing, proximal calculus and presence of subgingival A. actinomycetemcomitans, indicating current periodontitis. However, in the case group there were also children without positive signs of inflammatory disease, similar to the children in the reference group. In fact, the findings suggest that less than half of the number of individuals with > or = 2 proximal sites with bone loss had current periodontitis.

Role of cytokines in the modulation of neutrophil chemotaxis in localized juvenile periodontitis

Decreased neutrophil chemotaxis has been implicated in the pathophysiology of the disease, localized juvenile periodontitis (LJP). The biological basis for the altered neutrophil function in LJP has been suggested to be an intrinsic cellular defect, involving a decrease in the number of N-formyl-methionyl-leucyl-phenylalanine (FMLP) receptors on the cell surface. We have investigated the relative contribution of serum-borne factors in the modulation of neutrophil functions in LJP, in a large population of LJP patients and healthy control subjects (HS). Treatment of HS-neutrophils with LJP-sera, resulted in a decreased neutrophil chemotactic response, and down regulation of FMLP receptors on the cell surface. Pretreatment of LJP-sera with anti-TNF and anti-IL-1 antibodies effectively, although incompletely, neutralized the ability of LJP-sera to modulate chemotaxis and FMLP receptor levels in HS-neutrophils. The changes induced by LJP sera were specific and sustained and could not be reversed by placing LJP-serum treated neutrophils in HS-serum. Sera obtained from HS and patients with adult periodontitis (AP), both of which exhibit normal chemotaxis, and patients with clinically diagnosed LJP with normal neutrophil chemotaxis (LJP-nctx) did not modulate HS neutrophil chemotaxis or FMLP receptors. Furthermore, recombinant human TNF-alpha, rhIL-1 alpha and rhIL-1 beta, at very low concentrations (15 pg/ml to 150 pg/ml), modulated the chemotactic response as well as FMLP receptor numbers on HS-neutrophils, in a manner similar to those observed in LJP. The present findings demonstrate that the biologic basis for the altered neutrophil function may not be an intrinsic cellular defect in neutrophils, but at least in part due to quantitatively small but biologically significant elevations in the levels of TNF-alpha and IL-1 in the serum.

Flow cytometric determination of CD11b upregulation in vivo

We describe a flow cytometric method to evaluate upregulation of peripheral blood neutrophil and monocyte integrin CD11b in vivo. To avoid spontaneous upregulation in vitro, buffy coat cells were separated on ice and all subsequent cell handling steps were carried out at 0-4 degrees C. Such leukocytes were 95-100% viable, as determined by PI staining. Buffy coat leukocytes were double-stained with CD11b PE-conjugated and CD14 FITC-conjugated monoclonal antibodies and, in addition, with the nucleic acid dye LDS-751. After staining, firstly, LDS-751 positive (+ve) leukocytes, and, secondly, CD14 +ve monocytes were collected in live mode. Aggregated and irrelevant cells were gated out on the basis of their LDS-751 staining pattern and cellular light scattering properties, and the CD11b expression on neutrophils and monocytes was determined. Upregulation of CD11b in vitro was significantly affected by factors such as cell handling temperature, pre-fixation of blood samples, and density gradient separation of the cells. Incubation of aliquots of buffy coat cell suspension supplemented with FMLP for 5 min or without FMLP supplement for 15 min at 37 degrees C significantly increased CD11b expression without affecting cell viability. We have demonstrated that CD11b is expressed at maximal levels on arthritic synovial fluid neutrophils and CD14 +ve cells, and at increased but submaximal levels on peripheral blood neutrophils and monocytes of patients recovering from sepsis. The results suggest that the method can be used to evaluate in vivo upregulation of CD11b.

Functions of polymorphonuclear leukocytes in early rheumatoid arthritis

We carried out a prospective study on clinical variables and functions of polymorphonuclear leukocytes (PMNs) of 20 patients with early rheumatoid arthritis (RA) and compared the results with the presence of erosions before treatment and at a one-year follow-up. Migration of PMNs determined by agarose and filter assays and respiratory burst of PMNs determined by luminol-enhanced chemiluminescence (CL) test were studied both before starting RA-modifying treatment and 6-12 (mean 7.3) months later. PMNs of the patients without erosions at one year, as compared to the patients with erosions, showed significantly depressed migration into filter and significantly depressed CL responses to N-formyl-methionyl-leucyl-phenylalanine, both before starting the treatment and at 7.3 months. Although causality remains uncertain, the results suggest that depressed functional capacity of PMNs is associated with low risk of joint destruction in early RA.

Reevaluation of the chromosome 4q candidate region for early onset periodontitis

Evidence of linkage (lod = 3.1, theta = 0.05) was reported previously in one large kindred (the Brandywine genetic isolate) for an autosomal dominant form of early onset periodontitis (EOP) with a protein polymorphism in the vitamin D binding protein (GC) located on chromosome 4q12-q13. To evaluate the generality of this finding, 19 unrelated families (228 individuals), each with two or more EOP affected individuals, were ascertained and sampled. A restriction fragment length polymorphism (RFLP) at the GC locus and eight other polymorphic DNA markers and two red blood cell antigens located on proximal chromosome 4q in the vicinity of the GC locus were typed. Twelve genetic models of EOP were evaluated, which varied in diagnostic classification, penetrance, and mode of disease transmission. Results for all models strongly exclude linkage between an EOP susceptibility gene and this chromosomal region assuming locus homogeneity. Our data statistically exclude (lod < or = -2.0) the possibility that more than 40% of our families are linked to this candidate region for one model tested. Linkage under heterogeneity was excluded less strongly for other models, but no significant evidence in support of linkage was obtained for any model. Our results indicate that either the previous report of linkage was a false positive, or that there are two or more unlinked forms of EOP, with the form located in 4q12-q13 being less common.

Differential diagnosis in clinical trials of therapy for periodontitis

For purposes of clinical trials of therapies for periodontitis, it is recommended that population samples be identified as adult periodontitis (systemically modified or not systemically modified), early onset periodontitis (localized or juvenile, generalized or rapidly progressive, or associated with systemic disease), or necrotizing ulcerative periodontitis, avoiding overlapping criteria. Population samples of adult or early onset periodontitis modified by or associated with systemic conditions should be used in clinical trials only when the intent is to study effect on the specifically modified condition. Objective identification of the modifying systemic condition should be required for all subjects in such trials. Population samples should be homogeneous for the diagnosis, whether systemically modified or not. Refractory periodontitis, prepubertal periodontitis, and periodontitis associated with systemic disease are not recommended as useful descriptors of population samples without discrete identification of underlying systemic abnormality for all included subjects. Definition of population sample by a bacteriological or a host response feature is not recommended unless the trial is specifically aimed at that feature and the sample is homogeneous for it. All trials of efficacy should include physical or radiographic measurement of attachment level or bone height as a critical outcome variable. Results from trial in one form of periodontitis should not be applied directly to other forms.

Neutrophil modulation by Actinobacillus actinomycetemcomitans. II. Phagocytosis and development of respiratory burst

Compromised neutrophil function has been found in a number of patients with localized juvenile periodontitis (LJP), although the pathogenic mechanism is unknown. Since infection with Actinobacillus actinomycetemcomitans is frequently found in patients with LJP, we have evaluated in vitro the effect of a bacterial extract of A. actinomycetemcomitans on the development of the respiratory burst by neutrophils. Pre-incubation of neutrophils with bacterial extract increased H2O2 induced by FMLP and zymosan in a dose-dependent fashion. Substitution of FMLP for bacterial extract produced similar results. Moreover, FMLP and bacterial extract had an additive effect on superoxide production following phagocytosis of zymosan. In contrast, bacterial extract significantly decreased PMA-stimulated H2O2, but pre-incubation with FMLP instead of bacterial extract failed to decrease PMA-stimulated H2O2. Bacterial extract did not change the percentage of cells activated by FMLP, opsonized zymosan, or PMA. Heat-treated bacterial extract induced effects similar to non-treated extract. Bacterial extract treated with proteinase K or phenol extraction increased FMLP or zymosan stimulated H2O2 equivalent to non-treated bacterial extract. In contrast, proteinase K or phenol extraction abolished the inhibitory effect of bacterial extract on PMA-stimulated H2O2 production. The bacterial extract component(s) that inhibits PMA-stimulated H2O2 is therefore a protein(s), resistant to 56 degrees C, and is not endotoxin. The partially activated state of PMNs exposed to A. actinomycetemcomitans extract, combined with their reduced ability to respond to a protein kinase C-dependent stimulus, may partially explain the abnormalities noted in LJP patients.

Immunologic mechanisms of pathogenesis in periodontal diseases: an assessment

Principal lines of evidence that immune reactions are central to the pathogenesis of periodontitis are reviewed. Necessary components of immunologic reactions are present in gingiva in the periodontal diseases. Differences between healthy and periodontitis patients with respect to some measures of immune function further indicate that immune reactions do occur in the gingiva during periodontitis. They are probably responsible for at least some of the destruction of connective tissue and bone that occurs. Classical antibody-mediated hypersensitivity reactions probably do not provide the reasons. Mechanisms are more likely to be found in the pro-inflammatory and tissue-degrading effects of cytokines released in host-protective, antigen-specific and polyclonal responses to oral bacterial constituents or products. Some evidence suggests that limitation of clinical destruction in localized early onset periodontitis (JP) may in part be a function of a protective antibody response which develops after an initial rapidly progressive infection. A relatively deficient immune responsiveness may allow progression to more severe and generalized disease (RPP). Suggestions are made for studies needed to confirm suspected pathogenetic mechanisms, approach resultant targeted therapies, and test hypotheses for contrasting roles of immune reactions in different clinical expressions of periodontitis.