Blastogenic response and immunoglobulin production by inflamed gingival lymphocytes from dogs

Binding of Porphyromonas gingivalis gingipains to human CD4(+) T cells preferentially down-regulates surface CD2 and CD4 with little affect on co-stimulatory molecule expression

The role of Porphyromonas gingivalis cysteine proteinases (gingipains) in the evasion of host cell-mediated immunity has not been fully determined. In this study, modulation by gingipains of accessory and co-stimulatory molecule expression on human CD4(+) T cells was evaluated. Arg-gingipain rather than Lys-gingipain binds to resting CD4(+) T cells in the presence of serum. The constitutive expression of CD28 on T cells was slightly up-regulated following challenge with gingipains, whereas CD45 and CD3 were not affected. Binding of anti-CD2 and anti-CD4 monoclonal antibodies (mAbs) was reduced after challenge of T cells with gingipains, but restored to 50 and 100%, respectively, of control levels, after 48h of incubation in medium depleted of gingipains. The induced expression, by anti-CD3 mAb, of CTLA-4, CD25, and CD40 ligand (CD40L) was decreased following incubation of T cells with gingipains which also led to decreased response to anti-CD3 and anti-CD28 mAbs as shown by reduction of interleukin-2 (IL-2) production. Cumulatively, these results indicate that activated gingipains attach to T cells and preferentially cleave CD2 and CD4 molecules, with potential to impair T cell responses at periodontal sites.

Gingipains in the culture supernatant of Porphyromonas gingivalis cleave CD4 and CD8 on human T cells

Porphyromonas gingivalis has been shown to attack host defense systems through proteolytic cleavage of a wide variety of members of the systems. In this study, we examined the ability of P. gingivalis culture supernatant to alter the expression of human T cell surface proteins. As judged by flow cytometric analysis, detection of CD4 expression was completely eliminated by the supernatant, but CD8 was less sensitive. When the culture supernatant was added with reducing agents, proteolytic activity was enhanced, resulting in the cleavage of CD8. Mitogenic response of T cells to phytohemagglutinin or concanavalin A was decreased by the treatment of the cells with the culture supernatant of P. gingivalis. The three forms of gingipains (high molecular mass arginine-specific gingipain, arginine-specific gingipain 2 and lysine-specific gingipain) purified from the culture supernatant of P. gingivalis actively cleaved CD4 and CD8 on human T cells, indicating that proteolytic activity of the culture supernatant was due to gingipains. These results suggest that cysteine proteinases like gingipains released from P. gingivalis cleave T cell surface proteins and impede T cell function.

Identification and analysis of fipA, a Fusobacterium nucleatum immunosuppressive factor gene

We have previously demonstrated that sonic extracts of Fusobacterium nucleatum FDC 364 were capable of inhibiting human T-cell responses to mitogens and antigens. The purified F. nucleatum immunosuppressive protein (FIP) is composed of two subunits of 44 and 48 kDa. Furthermore, FIP inhibits T-cell activation by arresting cells in the middle of the G(1) phase of the cell cycle; the data available to date suggest that FIP impairs the expression of the proliferating-cell nuclear antigen. To initiate delineation of FIP structure-function relationships, molecular cloning of the FIP gene was carried out. A DNA library of F. nucleatum FDC 364 was constructed by partial digestion of genomic DNA with Sau3A and screened for the production of FIP with polyclonal antibody. Twelve immunoreactive clones were identified. One of these clones contained a 3.1-kbp insert and was chosen for further study. Cell lysates were found to contain an immunoreactive band that comigrated with the 44-kDa subcomponent of the native FIP. Sequencing of the 3.1-kpb insert revealed the presence of three open reading frames (ORFs). One ORF extends from nucleotides 415 to 1620, encodes 402 amino acids, and is preceded by a ribosome-binding site. Deletion analysis and antibody elution analysis showed that this ORF encodes the 44-kDa subunit (FipA) of native FIP. A second ORF is situated upstream of fipA. However, Northern (RNA) analysis suggested that fipA is not transcribed as part of an operon but transcribed from its own promotor. Finally, the partially purified recombinant FipA protein was capable of impairing T-cell activation in a manner consistent with the native protein. These results indicate that the two components that form the native protein are most probably distinct gene products and suggest that the 44-kDa FipA polypeptide is sufficient to mediate the immunosuppressive activities of the native protein complex.

Characterization of T lymphocyte clones derived from Porphyromonas gingivalis infected subjects

Porphyromonas gingivalis plays a major role in the pathogenesis of periodontal disease, however some individuals with P. gingivalis infection do not experience periodontal breakdown. The aim of this study was to investigate the proliferative responses of two highly defined groups of subjects and to establish and characterize peripheral blood and gingival cell T cell lines and clones from subjects from these groups. The two groups were selected on the basis of P. gingivalis in their plaque and the presence of serum anti-P. gingivalis antibodies. Both groups therefore were seen to have P. gingivalis and to have responded to it. They however differed only in their clinical susceptibility (adult periodontitis) or resistance (gingivitis) to periodontal breakdown. Dose responses of peripheral blood mononuclear cells extracted from the subjects showed a trend towards a lower response by the adult periodontitis group to P. gingivalis outer membrane (OM) antigens. Peripheral blood T cell lines and clones responsive to P. gingivalis OM were established from a high responding gingivitis subject and a low responding adult periodontitis subject. Gingival T cell lines and clones were also derived from cells extracted from the periodontal tissues of the same periodontitis subject. The majority of T cells in the peripheral blood T cell line from the gingivitis subject were CD4 while those from the adult periodontitis subject were CD8. The gingival T cell line was CD3+ve CD4-ve and CD8-ve. All lines and clones proliferated slowly to P. gingivalis OM but phytohaemagglutinin (PHA) induced an increase in DNA synthesis in those derived from the gingivitis subject with little to no effect on those established from the adult periodontitis subject. Furthermore, PHA inhibited the proliferative response of the CD8 clone derived from the adult periodontitis subject. Phenotypic analysis demonstrated that all the peripheral blood clones expressed the alpha beta TCR while the gingival T cell clones expressed the gamma-delta TCR. All clones had the memory/primed CD45RO+ve phenotype and at least 80% of cells in each clone were HLA-DR+ve. A lower percent of gingival cells expressed CD45RA than the CD4 peripheral blood clones and the two CD8 clones also had a decreased CD45RA expression. The gingival T cell clones also expressed a low percent CD25 as did the CD8 clone derived from the adult periodontitis subject. The results suggest that clones derived from the gingivitis and adult periodontitis subject may be functionally different. The presence of gamma-delta T cells in adult periodontitis remains to be confirmed and their function determined.

Serum and gingival crevicular fluid anti-desmosomal antibodies in periodontitis

SDS polyacrylamide gel electrophoresis separates desmosomal proteins and glycoproteins of bovine tongue epithelium by their relative molecular mass. The Western immunoblot technique was used to reveal the reactions of desmosomal proteins and glycoproteins with naturally occurring antibodies in serum and gingival crevicular fluid (GCF). Naturally-occurring serum and GCF antibodies (IgG and IgM) from periodontitis patients and healthy, unaffected controls reacted with desmosomal proteins (desmoplakins) and glycoproteins (desmogleins). Sera from 90% of subjects with periodontitis showed increased reactions of IgG with desmoplakins (240 and 210 kDa) and 80% with desmogleins (165, 130, and 115 kDa), when compared with unaffected controls. Patients' IgG reacted with desmosomal components more strongly than IgM. IgG antibodies against desmosomal antigens in GCF showed similar specificities from patients and healthy subjects and to their serums. When GCF within individuals with periodontitis was compared, anti-desmosomal IgG from diseased sites showed greater reactivity than healthy controls. These data suggest that anti-desmosomal antibodies are a normal part of the immune repertoire. The presence of elevated titers of anti-desmosomal antibodies appear to distinguish periodontitis from unaffected sites. When detected, elevated titers of anti-desmosomal antibodies may contribute to the pathogenesis and indicate increased risk of periodontitis.

Different responses in B cells induced by Porphyromonas gingivalis and Fusobacterium nucleatum

A phenotypic study had shown that gingival B cells respond differently to two periodontopathic bacteria, Porphyromonas gingivalis and Fusobacterium nucleatum. Further investigation now shows a reduction in the percentage of Ki-67 + T cells in cultures of gingival and peripheral blood mononuclear cells stimulated with P. gingivalis for 3 and 6 days, respectively, but no suppression of Ki-67 expression in B cells in response to either P. gingivalis or F. nucleatum. Depletion studies of cultures of peripheral blood mononuclear cells showed that in the absence of CD4 cells, the percentage of CD19+ and CD20+ B cells stimulated with P. gingivalis increased after 6 days whereas depletion of CD8 cells resulted in a rise in the percentage of F. nucleatum- and P. gingivalis-stimulated B cells, although this was not significant in the case of P. gingivalis. Specific antibody to P. gingivalis and F. nucleatum was found in culture supernatants of gingival but not of peripheral blood mononuclear cells, indicating a possible higher frequency of antigen-specific B cells in periodontal lesions. IgG was the predominant isotype in both gingival and control peripheral blood cultures, followed closely by IgA in gingival cultures. F. nucleatum stimulated higher levels of Ig in cultures of peripheral blood mononuclear cells than P. gingivalis or cells cultured in medium only, whereas in gingival cell cultures, stimulation by P. gingivalis appeared to result in higher levels of IgG. Also Ig was present at day 3 in gingival cultures, whereas in the blood cell cultures, Ig was only detected at day 6, further suggesting a degree of activation of of gingival B cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of, and anti-collagen antibody produced by, CD5-positive B cells in inflamed gingival tissues

This study was performed to investigate the frequency and distribution of CD5-positive (CD5+) B cells in inflamed gingival tissues using flow cytometric and immunohistochemical analyses. The ability of CD5+ B cells to produce anti-type I collagen antibody was also examined. CD5+ B cells expressed "low" fluorescence intensity in the peripheral blood of both healthy subjects and patients with adult periodontitis. However, in inflamed gingival tissues the intensity of this surface marker was high. The percentage of B cells bearing CD5 surface marker was statistically higher in gingiva than in peripheral blood obtained from both the patients and healthy subjects. These CD5+ B cells were observed in gingival subepithelial connective tissues from the bottom to the middle of the periodontal pocket. This area showed destruction of collagen fibers and dense cell infiltrations. Anti-collagen IgG antibody level in patients' gingival crevicular fluids (GCF) was higher than that in sera from healthy subjects, and slightly higher than in autologous sera. IgM anti-collagen antibody in GCF was lower than in autologous sera and in sera from healthy subjects. EBV-transformed CD5+ B cells produced considerably more IgM and IgG antibody to collagen than CD5- B cells. Therefore CD5+ B cells may contribute to the pathogenesis of inflamed gingival tissues.

CD45RA and CD45RO positive CD4 cells in human peripheral blood and periodontal disease tissue before and after stimulation with periodontopathic bacteria

Flow cytometric analysis was used to examine naive and primed or memory CD4 cells extracted from periodontal lesions compared with cells from peripheral blood of healthy subjects before and after stimulation with the periodontopathic bacteria, Porphyromonas gingivalis and Fusobacterium nucleatum. In peripheral blood, approximately 60% and 40% of CD4 cells were CD45RO+ and CD45RA+ respectively at day 0. Phytohaemagglutinin (PHA) induced CD45RO expression on almost 100% of CD4 cells. However, P. gingivalis and F. nucleatum stimulation did not cause any significant change in percentage of CD45RO+ CD4 cells except for a loss of antigen at day 6 together with re-expression at day 7, which also occurred on cells cultured in medium only. CD45RA expression on PHA and bacterial-stimulated peripheral blood CD4 cells remained fairly stable for the 10-d culture period. Greater than 90% CD4 cells extracted from healthy or marginal gingivitis (H/MG) and adult periodontitis (AP) lesions were CD45RO+ and this was maintained on AP cells throughout the 6-d culture period, except for a small decrease in the percentage of positive cells induced by P. gingivalis at day 3. Approximately 9% CD4 cells from H/MG tissue were CD45RA+, but about 22% AP cells expressed this antigen, and this increased again in P. gingivalis- and F. nucleatum-stimulated cultures after 3 d. Therefore, in peripheral blood P. gingivalis and F. nucleatum do not act as nonspecific T-cell mitogens and, in AP cells, these bacteria induce changes in phenotype, supporting previous data that although they may be polyclonal B-cell activators, they activate antigen specific T-cells.

Activated lymphocyte subsets in adult periodontitis*

The activation state of T and B lymphocytes in the peripheral blood of periodontitis patients may be a reflection of disease activity. We have utilized 2- and 3-color flow cytometric analyses using a new chromophore, peridinin chlorophyll A protein, and conventional dyes, fluorescein isothiocyanate and phycoerythrin, conjugated to monoclonal antibodies against activated lymphocyte surface markers to measure blood lymphocyte subsets from 18 periodontitis patients and 16 periodontally healthy control subjects. Two-color flow cytometric analysis demonstrated that the frequency of CD4+ and CD5+ T cells, CD20+ B cells, and CD16+ NK (natural killer) cells were increased in periodontitis patients. Of particular interest, CD4+ activated "memory" T cells, CD5+ B cells, and CD56+ NK effector cells were increased significantly in periodontitis patients (p less than 0.05). While the relationship of lymphocyte activation to periodontal disease activity remains unclear, there may be potential for using 2- and 3-color flow cytometry to subcategorize periodontitis patients into high- and moderate-risk groups.

Autoimmunity to collagen in adult periodontal disease: immunoglobulin classes in sera and tissue

The immunoglobulin class distribution of antibody to human collagen type I has been examined in sera and gingival extracts from patients with adult chronic periodontitis. Tissue extracts were made either by simple washing or ultrasonication. With either method, IgG and IgA antibodies to collagen were present in higher concentration in tissue extracts than in autologous serum when adjustment was made for dilution differences. No significant differences were found for IgM antibodies. Antibodies to human collagen type I are usually "natural antibodies" of the IgM class and, therefore, our findings suggest a class switch to IgG in inflamed gingivae, presumably due to prolonged antigenic stimulation.

Phenotypic analysis of B-cells extracted from human periodontal disease tissue

B-cells extracted from periodontal disease tissue were analyzed for the presence of activation markers using a range of monoclonal antibodies. In adult periodontitis (AP), 6% of B-cells expressed the IL-2 receptor (CD25) compared with 1-2% in peripheral blood and healthy or marginal gingivitis (H/MG) gingival B-cells. There was also an increase in the mean percentage of IgD-positive B-cells and a decrease in CD21 and CD22 expression. In both AP and H/MG lesions, 20-22% of the B-cells expressed CD23 compared with less than 5% in peripheral blood. As B-cells are activated by day 3 in culture and start differentiating into immunoglobulin-secreting cells by day 6, B-cell phenotypes were assayed at these times in this study. Following stimulation with the periodontopathic bacterium Porphyromonas gingivalis, the expression of CD23, CD21 and CD22 on B-cells extracted from AP lesions remained relatively constant over the 6-d culture period. However, with Fusobacterium nucleatum stimulation, there was a significant decrease in CD23, CD21 and CD22 expression after 3 d in culture, which corresponds to the activation time for B-cells. These results show that B-cells extracted from periodontal disease tissue display a range of activation markers and on stimulation, demonstrate differing responses to individual periodontopathic bacteria.

Expression of interleukin-2 receptor and HLA-DR on lymphocyte subsets of gingival crevicular fluid in patients with periodontitis

Expression of interleukin-2 receptor (IL2R) and HLA-DR on lymphocytes of gingival crevicular fluid (GCF) was examined by two-color flow cytometric analysis. GCF from 15 patients with periodontitis was collected by crevicular washing. Mononuclear cells were isolated by Ficoll-paque gradient centrifugation from inflamed gingival tissue (GT) and peripheral blood (PB) sampled from each of the 15 patients. Lymphocyte subsets were detected by using monoclonal antibodies (mAb) of Leu 12 (CD19), Leu 4 (CD3), Leu 3a (CD4) and Leu 2a (CD8) directed to B cells, T cells, helper/inducer T cells (Th) and suppressor/cytotoxic T cells (Ts), respectively. Anti-IL2R (CD25) and anti-HLA-DR were used as lymphocyte activation markers. IL2R- or HLA-DR-positive fractions in Th, Ts and B cells were calculated. Percentage of IL2R-positive fraction in Th (IL2R+ Th) of GCF (34.0%) was significantly higher than those of GT (18.4%) and PB (13.7%). IL2R-positive fraction in B cells (IL2R+ B) of GCF was the highest among the three groups (23.9% in GCF, 12.5% in GT, 6.3% in PB). Ts did not express IL2R regardless of the origin of the samples. Compared with PB and GT, GCF showed significantly higher HLA-DR expression on Th and Ts in GCF (PB: 8.7% and 27.1%; GT: 27.9% and 50.3%; GCF: 44.7% and 65.3%). These results suggest that lymphocytes in GCF were highly activated and are related to the local host immune response in periodontitis.