Effect of dietary omega-3 polyunsaturated fatty acids on experimental periodontitis in the mouse

Background and Objective:  Periodontitis is an infective disease caused predominantly by gram-negative anerobes. The host inflammatory response to these bacteria causes alveolar bone loss, which characterizes periodontitis. Omega-3 polyunsaturated fatty acids have recognized anti-inflammatory effects; their oxygenated derivatives are key mediators in reducing inflammation. In this study we tested the hypothesis that dietary supplementation with tuna fish oil rich in the n-3 polyunsaturated fatty acid, docosahexaenoic acid, would reduce alveolar bone loss in mice inoculated with periodontopathic bacteria.
Material and Methods:  Adult mice were fed experimental diets containing either 10% tuna oil or Sunola oil for 57 d. After 14 d, 35 mice on each diet were inoculated orally with Porphyromonas gingivalis , with a mixture of P. gingivalis and Fusobacterium nucleatum , with carboxymethylcellulose or remained untreated. The mice were killed, and soft tissue biopsies from the oral cavity of treated mice were used to determine the polyunsaturated fatty acid concentrations. The maxilla was removed, stained and digitally imaged to assess bone loss around the upper molars.
Results:  n-3 polyunsaturated fatty acid levels were significantly higher in oral soft tissues of mice fed tuna oil compared with the control group. Mice fed tuna oil and inoculated with P. gingivalis or with the combination of F. nucleatum and P. gingivalis exhibited 72% and 54% less alveolar bone loss respectively, compared with the treatment control group.
Conclusion:  Alveolar bone loss was inversely related to n-3 polyunsaturated fatty acid tissue levels. In conclusion, fish oil dietary supplementation may have potential benefits as a host modulatory agent in the prevention and/or adjunctive management of periodontitis.     

牙龈卟啉单胞菌在牙周病防治中的应用

牙周病是口腔两大类主要疾病之一,具有较高的发病率,因此,探索预防牙周病的有效途径十分重要。本文介绍了国外学者以牙龈卟啉单胞菌不同形式的抗原进行免疫学防治牙周炎的试验,其中包括对牙龈卟啉单胞菌菌毛、血凝素、牙龈素和外膜蛋白的研究。     

牙龈卟啉单胞菌脂蛋白基因在慢性牙周炎及牙周健康者中的检测

目的 应用基因芯片技术检测3种脂蛋白基因PG0717、PG0183、PG2135在慢性牙周炎患者和牙周健康者牙龈卟啉单胞菌(Porphyromonas gingivalis,Pg)中的分布,探讨这些基因与牙周临床指数之间的关系,为研究脂蛋白在Pg致病过程中的作用提供依据.方法 选取41例慢性牙周炎患者(牙周炎组)及76例牙周健康者(健康对照组),记录探诊深度、附着丧失、探诊出血及牙齿松动度,取龈下菌斑进行细菌分离培养,以临床采集的样本提取的DNA为探针,以抑制消减杂交技术获得的PgW83特异基因片段PG0717、PG0183、PG2135为目标序列,采用Cy5荧光标记目标序列.应用基因芯片技术检测PG0717、PG0183、PG2135基因在牙周炎组病变部位、非病变部位和健康对照组Pg中的分布.结果在牙周炎组病变部位PG0717、PG0183、PG2135基因的检出率分别为90%(18/20)、70%(14/20)、70%(14/20),非病变部位的检出率分别为60%(12/20)、45%(9/20)、40%(8/20),而在健康对照组PG0717、PG0183、PG2135的检出率分别为55%(11/20)、25%(5/20)、30%(6/20).3种脂蛋白基因在牙周炎组病变部位和健康对照组中的检出率差异均有统计学意义(P＜0.05),并且与牙周探诊深度、临床附着丧失、探诊出血及牙齿松动度相关.结论 带有PG0717、PG0183、PG2135基因的Pg菌株致病力强.     

Antimicrobial susceptibility variation of 50 anaerobic periopathogens in aggressive periodontitis: an interindividual variability study

BACKGROUND/AIMS: The frequent use of antibiotics in developed countries has led to the emergence of widespread bacterial resistance. In this study, the interindividual variability of the antibiotic susceptibility of 50 putative microorganisms in aggressive periodontitis patients has been evaluated by means of VC (variation coefficient). MATERIAL AND METHODS: A total of 60 microbial samples were collected from 20 adult patients diagnosed with aggressive periodontitis (2-4 samples by patient). Bacterial strains of Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, Fusobacterium nucleatum, and Peptostreptococcus micros were isolated according to Slots' rapid identification method. The susceptibilities to 10 antibiotics were studied: penicillin G (PEN), ampicillin (AMP), amoxicillin (AMX), amoxicillin/clavulanate (AMC), tetracycline (TET), doxycycline (DOX), ciprofloxacin (CIP), erythromycin (ERY), spiramycin (SPI) and clindamycin (CLIN), using the Disk Diffusion Susceptibility test (DDS test: Kirby-Bauer's modified method for anaerobic bacteria). The broth microdilution Minimum Inhibitory Concentration test was carried out as a control test. RESULTS: Among the 50 identified bacteria, 15 were P. gingivalis, 12 P. intermedia, 8 T. forsythia, 9 F. nucleatum, and 6 P. micros. The results of the DDS test show that penicillins (especially AMC, AMP, and AMX), cyclines (especially DOX) and CLIN are highly effective against the 50 anaerobic studied bacteria. CIP and ERY have the lowest efficacy against those bacteria. CIP shows a very variable activity according to anaerobic bacteria species, being particularly inactive against P. gingivalis and very efficient against T. forsythia and P. micros. SPI is also highly efficient but not against P. micros. CONCLUSIONS: The interindividual susceptibility of principal periodontal pathogens to antibiotics is not homogeneous and seems to vary according to bacterial species and antimicrobial molecules. This variability seems to be greater with older molecules (PEN, TET, ERY) than with more recent ones, which indicates more stable results (AMC, AMX, AMP, and DOX). P. intermedia appeared to be the bacteria most resistant to penicillins and showed the highest coefficient variation. Together with scaling and root planing, the combination of two antibiotics would therefore seem to be recommended in the treatment of aggressive periodontitis, particularly in the presence of P. intermedia.     

Immunoglobulin G subclass antibody profiles in Porphyromonas gingivalis-associated aggressive and chronic periodontitis patients

BACKGROUND/AIMS: The immunoglobulin G (IgG) antibody response is considered to be protective and beneficial for the control of periodontal lesions. This study analysed IgG subclass antibody levels of Porphyromonas gingivalis in patients with both aggressive periodontitis (AgP) and chronic periodontitis (CP). METHODS: Subgingival plaque and peripheral blood samples were collected from patients with localized AgP (n = 13), generalized AgP (n = 28) and generalized CP (n = 27) and from 14 periodontally healthy controls. P. gingivalis was identified in subgingival pockets using a polymerase chain reaction. Simultaneously, serum IgG subclass antibody against P. gingivalis whole cells/P. gingivalis fimbriae were measured using enzyme-linked immunosorbent assay. RESULTS: P. gingivalis was frequently detected in periodontitis patients. Anti-P. gingivalis whole cell IgG1 was elevated in all P. gingivalis-positive patients in the three periodontitis groups. Although increased anti-P. gingivalis IgG1 was also observed in the bacterium-positive healthy controls, the level was lower than that found in the three periodontitis groups. Levels of IgG1, IgG2, IgG3 and IgG4 to P. gingivalis did not differ among bacterium-positive patients in the three periodontitis groups; a significant increase of IgG2 level was not observed in localized AgP. Anti-fimbriae IgG subclass levels of IgG1, IgG2 and IgG4 did not differ among bacterium-positive subjects in all groups, while the anti-fimbriae IgG3 level in generalized CP was significantly higher than that in localized and generalized AgP. CONCLUSIONS: P. gingivalis infection elicited an IgG subclass antibody response in both periodontitis patients and healthy subjects, while higher anti-P. gingivalis IgG1 levels were found in the three periodontitis groups compared with the healthy control group.     

牙龈卟啉单胞菌PG1055基因在临床菌株中的表达

目的应用基因芯片技术检测PG1055基因在不同人群的牙龈卟啉单胞菌(P.gingivalis)中分布,探讨这些基因与牙周临床指数之间的关系。方法取龈下菌斑进行细菌分离培养,以临床采集样本提取的DNA为探针,以抑制消减杂交技术获得P.gingivalisW83的特异基因片段PG1055为目标序列,采用Cy5荧光标记目标序列。应用基因芯片技术检测PG1055基因在牙周病患者及健康人群的牙龈卟啉单胞菌中的分布。结果PG1055基因在牙周病患者及健康人群中的检出率有统计学差异,并且与牙周临床指数相关。结论PG1055基因与P.gingivalis的致病性有关。     

牙龈卟啉菌、中间普氏菌的分离、培养和鉴定

目的：采用厌氧培养和鉴定技术，分离牙周炎患者龈下菌斑中的牙龈卟啉菌和中间普氏菌。方法：采集牙周炎患者的龈下菌斑，厌氧培养，分离产黑色素菌。经长波长紫外灯观察，各种生化分析和间接免疫荧光染色，分离和鉴定牙龈卟啉菌，中间普氏菌。结果：在受检的33例牙周炎患者中，24例患者检出了牙龈卟啉菌，总检出率为72．77％，共分离了79株。18例患者检出了中间普氏菌，总检出率为54．54％。共分离了32株。结论：厌氧培养，生化反应鉴定技术的发展，使牙龈卟啉菌和中间普氏菌的分离与培养准确可靠，为今后在分子水平上了解各菌株的致病机理打下了基础。     

Immunoglobulin G subclass antibody profiles in Porphyromonas gingivalis‐associated aggressive and chronic periodontitis patients

Background/aims: The immunoglobulin G (IgG) antibody response is considered to be protective and beneficial for the control of periodontal lesions. This study analysed IgG subclass antibody levels of Porphyromonas gingivalis in patients with both aggressive periodontitis (AgP) and chronic periodontitis (CP). Methods: Subgingival plaque and peripheral blood samples were collected from patients with localized AgP (n = 13), generalized AgP (n = 28) and generalized CP (n = 27) and from 14 periodontally healthy controls. P. gingivalis was identified in subgingival pockets using a polymerase chain reaction. Simultaneously, serum IgG subclass antibody against P. gingivalis whole cells/P. gingivalis fimbriae were measured using enzyme‐linked immunosorbent assay. Results: P. gingivalis was frequently detected in periodontitis patients. Anti‐P. gingivalis whole cell IgG1 was elevated in all P. gingivalis‐positive patients in the three periodontitis groups. Although increased anti‐P. gingivalis IgG1 was also observed in the bacterium‐positive healthy controls, the level was lower than that found in the three periodontitis groups. Levels of IgG1, IgG2, IgG3 and IgG4 to P. gingivalis did not differ among bacterium‐positive patients in the three periodontitis groups; a significant increase of IgG2 level was not observed in localized AgP. Anti‐fimbriae IgG subclass levels of IgG1, IgG2 and IgG4 did not differ among bacterium‐positive subjects in all groups, while the anti‐fimbriae IgG3 level in generalized CP was significantly higher than that in localized and generalized AgP. Conclusions: P. gingivalis infection elicited an IgG subclass antibody response in both periodontitis patients and healthy subjects, while higher anti‐P. gingivalis IgG1 levels were found in the three periodontitis groups compared with the healthy control group.     

Immunodominant antigens of Porphyromonas gingivalis in patients with rapidly progressive periodontitis

We studied 4 isolates of Porphorymonas gingivalis , ATCC 33277, 381, A7A1-28, and W50, to identify major cell surface antigens and select the best strain from which to obtain antigen for a test vaccine. Immunoglobulin G (IgG) titers measured by enzyme-linked immunosorbent assay using whole-cell sonicates as antigen were significantly elevated for the sera of 64 rapidly progressive periodontitis patients relative to sera of 30 normal control subjects for each of the 4 strains studied. Western blots were prepared for all 4 strains and developed using sera from 22 patients and 20 control subjects to identify and determine the frequency of antibody-binding components. The intensity of binding by patient sera was greatest for the 75-kDa and 55-kDa components. The 43-kDa component was also widely recognized. Strains ATCC 33277 and 381 appeared to be antigenically similar. Because of the higher serum antibody titers, the larger proportion of seropositive patients and higher frequency of binding to specific protein components in Western blots, our efforts were focused on strain ATCC 33277. Whole-cell sonicates, proteinase K-digested sonicate, lipopolysaccharide, capsular polysaccharide, and whole-cell protein fractions were prepared and evaluated for anti-genie activity. By dot immunoblot, most of the antibody binding activity was found in the whole-cell protein fraction, with much lesser amounts in lipopolysaccharide and none in capsular polysaccharide. The antibody-binding activity was accessible on the cell surface, since 98.9% of P. gingivalis -specific antibody, including antibody binding to the 43-kDa, 55-kDa and 75-kDa components on Western blot, was removed by whole-cell adsorption. Furthermore, the 43-kDa and 55-kDa but not the 75-kDa component on intact cells were accessible for labeling with 125_I, confirming their cell surface location and accessibility.     

Antibody reactive with Porphyromonas gingivalis hemagglutinin in chronic and generalized aggressive periodontitis

BACKGROUND: Porphyromonas gingivalis, a black-pigmented, gram-negative anaerobe, is found in periodontitis lesions and its presence in subgingival plaque significantly increases the risk for periodontitis. We have previously shown that patients with aggressive forms of periodontitis that are seropositive for P. gingivalis have less attachment loss than those that are seronegative. This suggests that antibody reactive with antigens of P. gingivalis may be protective and decrease disease severity and extent. Recent studies in the murine abscess model and in the host antibody response in chronic periodontitis patients suggest that antibody reactive with P. gingivalis hemagglutinin may be an important protective antibody response. OBJECTIVES: In this study, we tested the hypothesis that there was a significant relationship between antibody reactive with P. gingivalis hemagglutinin and measures of periodontal attachment loss. METHODS: We determined the immunoglobulin G (IgG) antibody concentration reactive with recombinant P. gingivalis hemagglutinin in 117 chronic periodontitis and 90 generalized aggressive periodontitis patients. We also determined the IgG subclass distribution for antibody reactive with P. gingivalis hemagglutinin. RESULTS AND CONCLUSIONS: We found IgG reactive with P. gingivalis hemagglutinin in both chronic periodontitis and generalized aggressive periodontitis patients. Most of this IgG antibody was of the IgG1 and IgG3 subclasses. Antibody reactive with P. gingivalis hemagglutinin, however, did not have a significant relationship with measures of periodontal attachment loss.     

Herpesvirus-bacteria synergistic interaction in periodontitis

The etiopathogenesis of severe periodontitis includes herpesvirus-bacteria coinfection. This article evaluates the pathogenicity of herpesviruses (cytomegalovirus and Epstein-Barr virus) and periodontopathic bacteria (Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis) and coinfection of these infectious agents in the initiation and progression of periodontitis. Cytomegalovirus and A. actinomycetemcomitans/P. gingivalis exercise synergistic pathogenicity in the development of localized (“aggressive”) juvenile periodontitis. Cytomegalovirus and Epstein-Barr virus are associated with P. gingivalis in adult types of periodontitis. Periodontal herpesviruses that enter the general circulation may also contribute to disease development in various organ systems. A 2-way interaction is likely to occur between periodontal herpesviruses and periodontopathic bacteria, with herpesviruses promoting bacterial upgrowth, and bacterial factors reactivating latent herpesviruses. Bacterial-induced gingivitis may facilitate herpesvirus colonization of the periodontium, and herpesvirus infections may impede the antibacterial host defense and alter periodontal cells to predispose for bacterial adherence and invasion. Herpesvirus-bacteria synergistic interactions, are likely to comprise an important pathogenic determinant of aggressive periodontitis. However, mechanistic investigations into the molecular and cellular interaction between periodontal herpesviruses and bacteria are still scarce. Herpesvirus-bacteria coinfection studies may yield significant new discoveries of pathogenic determinants, and drug and vaccine targets to minimize or prevent periodontitis and periodontitis-related systemic diseases.     

Response of periodontitis and healthy patients in a Porphyromonas gingivalis‐stimulated whole‐blood model

Aim: To investigate the inflammatory responses of periodontitis patients and healthy patients in a whole‐blood model stimulated with Porphyromonas gingivalis. Methods: Whole blood collected from 17 periodontitis patients and six healthy patients was stimulated with Porphyromonas gingivalis cells. The secretion of cytokines and matrix metalloproteinases was quantified by enzyme‐linked immunosorbent assay. An analysis of covariance with the ancova model was used to evaluate the significance of differences in secreted host molecules by whole blood from the periodontitis and healthy groups. Results: Porphyromonas gingivalis induced the secretion of interleukin‐1β, interleukin‐6, interleukin‐8, tumor necrosis factor‐α, monocyte chemoattractant protein‐1, interferon inducible protein‐10 by whole blood from patients in the periodontitis and healthy groups. Matrix metalloproteinase‐8 and ‐9 levels secreted by whole blood also increased following stimulation. No significant differences (P < 0.05) in the amounts of secreted host molecules were observed between periodontitis and healthy patients. Conclusion: This study suggests that Porphyromonas gingivalis can provoke an inflammatory response and promote the progression of periodontitis by inducing the secretion of high levels of cytokines and matrix metalloproteinases by a mixed leukocyte population. However, the whole‐blood model did not reveal any significant differences in the inflammatory response between periodontitis patients (n = 17) and periodontally‐healthy patients (n = 6).     

Trypsin-like activity levels of Treponema denticola and Porphyromonas gingivalis in adults with periodontitis

Abstract Treponema denticola (Td) and Porphyromonas gingivalis (Pg) are associated with human moderate and severe adult periodontal diseases. This study Quantifies these two anaerobes and their trypsin-like (TL) activities in subgingival plaque collected from both clinically healthy and periodontally diseased sites of human periodontitis patients. Antigen levels of the microorganisms were determined by monoclonal antibodies and TL activities were measured by the fluorescent substrate Z-gly-gly-arg-AFC in a disc format. Significant positive correlations were observed between the antigen levels and the TL activities when the data were subjected to statistical analyses both on a site-specific and on a patient basis. Anaerobe synergism was found between Td and Pg in a continental US population, and positive correlations were found between anaerobe levels (individually and total) and clinical indicators of adult periodontitis.     

Analysis of cultivable Porphyromonas gingivalis with trypsin-like protease enzyme activity and serum antibodies in chronic adult periodontitis

OBJECTIVE: Trypsin-like protease (TLPase) enzyme produced by Porphyromonas gingivalis has been implicated as a virulence factor in the pathogenesis of periodontal disease. The aims of this study were to investigate the relationship between cultivable P. gingivalis , TLPase enzyme activity (BANA hydrolysis) and serum antibody levels against cell sonicate and a purified TLPase antigen from P. gingivalis W50.
MATERIALS AND METHODS: Sub-gingival plaque samples were cultured for levels of P. gingivalis together with a chairside analysis of TLPase enzyme activity (Perioscan) from periodontitis and gingivitis sites of adult periodontitis patients. A TLPase from P. gingivalis was purified by gel filtration and ion exchange chromatogra-phy from the vesicle fraction for use as a test antigen. RESULTS: Elevated levels of P. gingivalis were found at periodontitis sites, however, there was no correlation with sub-gingival plaque TLPase enzyme activity. Adult periodontitis patients had higher levels of IgG and IgA against cell sonicate and TLPase antigens than did controls. Those patients who were P. gingivalis culture-positive demonstrated an elevated immune response against both cell sonicate and TLPase when compared to P. gingivalis culture-negative patients. Treatment resulted in an improvement of clinical indices and no cultivable P. gingivalis could be recovered from the treated sites and there was a concomitant decrease in IgG levels against the TLPase. There was no significant difference in BANA hydrolysis at gingivitis sites or periodontitis sites after treatment.
CONCLUSIONS Further longitudinal studies are suggested to investigate the role of the TLPase in the response to treatment of chronic adult periodontitis patients.     

牙周炎与不良妊娠结局相关关系的研究进展

牙周炎是由牙周致病菌感染引起的慢性炎症性疾病,在妊娠妇女中更容易发生。不良妊娠结局是新生儿围产期死亡的重要原因,受机体全身炎症的影响。该文主要对牙周炎与不良妊娠结局的相关性进行阐述,进一步从阴道感染、菌血症、免疫炎症和肠道菌群方面对其机制进行探讨,并简述了牙周炎与不良妊娠结局共有的宿主易感性遗传背景,以期为临床上预防妊娠期牙周病和不良妊娠结局提供一定的理论指导。     

Immune responses to heat shock protein in Porphyromonas gingivalis-infected periodontitis and atherosclerosis patients

BACKGROUND: It has been widely thought that heat shock protein might be involved in autoimmune disease mechanisms in humans. OBJECTIVES: The present study was performed to evaluate the recognition of Porphyromonas gingivalis heat shock protein 60 (hsp60) and human hsp60 by immune sera in P. gingivalis-infected periodontitis and atherosclerosis patients. MATERIALS AND METHODS: Mononuclear cells from atheroma lesions were stimulated with P. gingivalis hsp and sera from periodontitis or atherosclerosis patients were subjected to Western immunoblotting to P. gingivalis hsp or human hsp, respectively. RESULTS: Western immunoblot analysis demonstrated the dual reactivity of anti-P. gingivalis antisera with P. gingivalis hsp and human hsp. We could also establish P. gingivalis hsp-specific T cell lines from the atheroma lesions, a mixture of CD4+ and CD8+ cells producing the cytokines characteristic of both Th1 and Th2 subsets. CONCLUSION: These observations suggest the modulating effect of P. gingivalis hsp60 in the immunopathogenesis of periodontitis and atherosclerosis.     

Strain-dependent activation of the mouse immune response is correlated with Porphyromonas gingivalis-induced experimental periodontitis

Aims: To evaluate the effect of oral infection with three Porphyromonas gingivalis strains on alveolar bone loss (ABL) and its correlation with the mouse immune response.
Materials and Methods: Mice were orally infected with P. gingivalis strains 381, 33277 and 53977. After 42 days, maxillae were analysed for ABL using micro-computed tomography and the serum for anti- P.gingivalis IgG1 and IgG2a levels. The cytokine response to P. gingivalis was tested using the subcutaneous chamber model.
Results: The P. gingivalis 53977-infected group showed the highest ABL, which was significantly different from all other groups ( p <0.001). In addition, the humoral response to P. gingivalis 53977 was significantly lower than the response to P. gingivalis 381 and 33277 ( p 0.01). The IgG2a/IgG1 ratio was higher in the P. gingivalis 33277-infected group (1.6) compared with the P. gingivalis 381-infected group (0.51). Four days post-infection, interleukin (IL)-1 β levels remained significantly higher in the P. gingivalis 53977-infected group only (1198.2±260.0, p <0.05), while IL-4 levels remained significantly higher in the P. gingivalis 381-infected group (265.8±131.6, p <0.05).
Conclusions: The high levels of ABL induced by P. gingivalis 53977 were inversely correlated with the humoral response to this bacterium. In addition, ABL was correlated with an elevated pro-inflammatory response.     

牙龈卟啉菌核酸探针在临床尖周炎检测中的应用

随机选择门诊尖周炎患者１００人，采用无菌纸捻从根管内吸取标本，用核酸探针杂交技术进行检测。结果显示：慢性尖周炎中Ｐｇ阳性率为７３．２４％，慢性尖周炎急性发作时Ｐｇ检出率为８２．７６％，但二者无统计学差异（Ｐ〉０．０５）；Ｐｇ与尖周炎临床症状中的自发痛、叩痛、臭味和尖周肿胀有关（数据均有统计学差异），而与有无窦道无显著差异（Ｐ〉０．０５）；提示Ｐｇ与尖周炎临床症状有密切关系。核酸探针适用于直接检测临     

Humoral immune responses to Porphyromonas gingivalis before and following therapy in rapidly progressive periodontitis patients.

We have performed studies aimed at elucidating the nature of the humoral immune response in rapidly progressive periodontitis (RPP). We analyzed the sera of 36 periodontally normal subjects and 36 RPP patients for titers and avidities of IgG antibodies reactive with the antigens of Porphyromonas gingivalis using ELISA, prior to and following treatment. We used whole-cell sonicate, purified lipopolysaccharide (LPS), and total extractable protein as plate antigens. Twelve of the patients had antibody titers at least 2-fold greater than the median of the controls and were designated as seropositive. The remaining 24 patients had titers that did not exceed twice the median titer of the controls and were designated as seronegative. For both patient groups, antibody titers were highest when whole-cell antigen was used, intermediate for LPS, and lowest for the protein fraction. Following treatment, median titer for seropositive patients decreased from pretreatment values of 241.7 to 76.5, while median titer for seronegative patients increased from 39.5 to 80.1. Avidities of pretreatment sera from both patient groups for all 3 antigen preparations were lower than the median avidities of the control sera. Avidity significantly increased following treatment to levels greater than those for control sera in both patient groups. Thus, some young adults with severe periodontitis mount a humoral immune response and produce high levels of serum IgG antibodies reactive with antigens of P. gingivalis, while others do not. The antibodies produced are of relatively low avidity, and may therefore be relatively ineffective biologically. Therapy, which greatly reduces antigen load, appears to stimulate production of higher avidity IgG antibodies in both patient groups; in the seropositive group, low avidity antibodies appear to be replaced by antibodies of higher avidity. Both the purified LPS and protein fractions contain reactive antigen(s), although LPS binds more antibody. Our data are consistent with the idea that many RPP patients do not produce protective levels of biologically functional antibody during the course of their natural infection, but they may be stimulated to do so by treatment.