An immunoperoxidase technique was used to examine CD28, CD152, CD80 and CD86 positive cells in gingival biopsies from 21 healthy/gingivitis and 26 periodontitis subjects. The samples were placed into 3 groups (small, intermediate, large) according to the size of the infiltrate. The percent CD28+ T cells in the connective tissue infiltrates was highly variable with no differences between the healthy/gingivitis and periodontitis groups. While there was an increase in positive cells in intermediate infiltrates from both healthy/gingivitis (28.5%) and periodontitis (21.4%) patients compared with small infiltrates (8.6% and 11.8%, respectively), this was not significant, although the percent CD28+ T cells did increase significantly in tissues with increased proportions of B cells relative to T cells (p=0.047). A mean of less than 5% infiltrating T cells were CD152+ which was significantly lower than the mean percent CD28+ T cells in intermediate healthy/gingivitis lesions (p = 0.021). The mean percent CD80+ and CD86+ B cells and macrophages was 1-7% and 8-16%, respectively, the difference being significant in intermediate healthy/gingivitis tissues (p = 0.012). Analysis of these cells in relation to increasing numbers of B cells in proportion to T cells and also to macrophages, suggested that CD80 was expressed predominantly by macrophages while CD86 was expressed by both macrophages and B cells. Few endothelial cells expressed CD80 or CD86. Keratinocytes displayed cytoplasmic staining of CD80 rather than CD86 although the numbers of positive specimens in the healthy/gingivitis and periodontitis groups reduced with increasing inflammation. In conclusion, percentages of CD28, CD152, CD80 and CD86 did not reflect differences in clinical status. However, the percent CD28+ T cells increased with increasing size of infiltrate and with increasing proportions of B cells suggesting increased T/B cell interactions with increasing inflammation. The percent CD152+ cells remained low indicating that CD152 may not be involved in negative regulation of T cells in periodontal disease. CD80 and CD86 have been reported to promote Th1 and Th2 responses, respectively, and the higher percent CD86+ cells suggests a predominance of Th2 responses in both healthy/gingivitis and periodontitis tissues. Nevertheless, other factors including cytokines themselves and chemokines which modulate T cell cytokine profiles must be monitored to determine the nature of Th1/Th2 responses in periodontal disease.

This study has shown that genetic differences at the level of H-2 haplotype induce variations in the local and T and B cell responses to P. gingivalis antigens. The responses of DBA/2J mice which have the same haplotype as BALB/c mice suggest that factors other than H-2 haplotype such as the C5 deficiency may influence this immune response. The significance of the specific antibody and T cell responses and of their inverse relationship to susceptibility to periodontal disease remains to be determined.

Cytokines produced by T-cells in periodontal lesions may determine the nature of the adaptive immune response. Since different antigen-presenting cells (APC) may direct the Th1/Th2 response, P. gingivalis-specific T-cell lines were established by different APC subpopulations, and their cytokine profiles were determined. Peripheral blood mononuclear cells induced similar percentages of IL-4+ and IFN-gamma+ T-cells and lower percentages of IL-10+ T-cells. Epstein-Barr virus-transformed B-cells (LCL) induced higher percentages of IL-4+ cells than IFN-gamma+ cells, with lower percentages of IL-10+ cells. Peripheral blood mononuclear cells induced a higher percent of IFN-gamma+ CD8 cells than LCL (p = 0.004). Purified B-cells, monocytes, and dendritic cells induced similar percentages of IL-4+ and IFN-gamma+ cells, although again, the percentage of IL-10+ cells was lower. The results of the present study have demonstrated that, as measured by FACS analysis of intracytoplasmic cytokines, P. gingivalis-specific T-cells produce both Th1 and Th2 cytokines, regardless of the APC population.

FACS analysis was used to determine the expression of 15 T-cell receptor V beta families on CD4 and CD8 cells in Porphyromonas gingivalis specific T-cell lines established from eight P. gingivalis-positive adult periodontitis and seven P. gingivalis-positive healthy or gingivitis subjects. All 15 T-cell receptor V beta families were expressed by the T-cell lines, although a significantly higher proportion of the CD4 cells expressed the 5.2-3 V beta region compared with the other 14 families, including the 5.3 region, suggesting that it is the 5.2 family which is overexpressed. This was also true for the CD8 cells, with the exception of the 3.1 region in adult periodontitis T-cell lines and the 3.1, 13.1/13.3 and 21.3 regions in healthy or gingivitis lines. Between the two clinical groups, a significantly lower percentage of 13.1/13.3-positive CD8 cells was noted in the adult periodontitis lines compared with the healthy or gingivitis lines. There was a significant reduction in DNA synthesis by the lines in the presence of P. gingivalis outer membrane antigens and fixed irradiated lymphoblastoid cell lines compared with cultures containing untreated irradiated lymphoblastoid cell lines and in cultures containing anti-class II major histocompatibility complex antibody in comparison with all other cultures. The results of this study have shown that P. gingivalis preferentially induces the T-cell receptor V beta 5.2 family on CD4 and CD8 cells in P. gingivalis-specific T-cell lines and that activation of T cells by P. gingivalis outer membrane antigens may be by antigen-specific rather than superantigen activity.

T-cell cytokine profiles in ten adult periodontitis and seven age-matched healthy or gingivitis subjects were determined. Porphyromonas gingivalis-specific T-cell lines were established from the peripheral blood of these individuals all of whom had past or present evidence of P. gingivalis infection. FACS analysis was used to determine the percentage of CD4- and CD8-positive cells in each line staining for cytoplasmic interleukin (IL)-4, interferon-gamma and IL-10. There were no differences in the mean percentage of IL-4-, interferon-gamma- or IL-10-positive T cells between the two groups. However, the individual profiles showed that the CD4 cells in five of the seven healthy or gingivitis lines had a higher proportion of interferon-gamma-positive cells, with two lines demonstrating higher percentages of IL-10- and/or IL-4-positive CD4 cells. Five of the ten adult periodontitis lines demonstrated either equal or higher percentages of IL-4-positive and/or IL-10-positive CD4 cells. With respect to the CD8 cells, two of the seven lines established from the healthy or gingivitis subjects and six of the ten adult periodontitis lines showed profiles with a higher percentage IL-4- and/or IL-10-positive cells. When the total T-cell contribution (CD4 plus CD8) for each T-cell line was determined from the individual CD4:CD8 ratios, only one of the healthy or gingivitis lines showed a profile with a higher proportion of IL-10-positive cells, while the results for the adult periodontitis lines were the same as indicated for the CD4 cell profiles, with five lines showing a higher percentage of IL-4- and/or IL-10-positive cells. In conclusion, this study has shown that in P. gingivalis-responsive T-cell lines established from adult periodontitis and healthy or gingivitis subjects, there was a predominant trend towards a higher percentage of interferon-gamma positive cells than either IL-4- or IL-10-positive cells. However, there were variations from this trend, although whether these variations indicate true susceptibility to progressive disease has yet to be determined.