Cytokine induction by Streptococcus mutans and pulpal pathogenesis - PubMed (original) (raw)

Cytokine induction by Streptococcus mutans and pulpal pathogenesis

C L Hahn et al. Infect Immun. 2000 Dec.

Abstract

Chronic pulpal inflammation under caries appears to be elicited by bacterial antigens that diffuse into the pulp through dentinal tubules. This prompted the hypothesis that cytokines elicited by antigens from Streptococcus mutans, which frequently dominates shallow lesions, could play a major role in eliciting the initial T-cell response in the pulp. To test this, we examined the ability of S. mutans to stimulate T cells and elicit cytokines and used Lactobacillus casei, which often predominates in deep carious lesions where B cells and plasma cells predominate, as a control. In addition, the presence of cytokines in the pulp was analyzed at the mRNA level. S. mutans elicited potent gamma interferon (IFN-gamma) responses in peripheral blood mononuclear cell cultures and reduced the CD4/CD8 ratio by promoting CD8(+) T cells. Multiple inflammatory cytokine mRNAs (IFN-gamma, interleukin 4 [IL-4], and IL-10) were detected in human dental pulp. A higher prevalence of IFN-gamma (67%) than IL-4 (19%) or IL-10 (29%) was obtained in shallow caries, suggesting a type 1 cytokine mechanism in early pulpitis where S. mutans predominates. In contrast, in deep caries no differences in cytokine frequency were observed. Furthermore, the presence of IFN-gamma in the pulp correlated with the presence of S. mutans. The extraordinary induction of type 1 cytokines and the preferential activation of CD8(+) T cells by S. mutans offers an explanation for the etiology of the CD8(+) T-cell-dominant lesion in early pulpitis and suggests that S. mutans may have a major impact on the initial lesion and pulpal pathology.

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Figures

FIG. 1

FIG. 1

Comparison of S. mutans and L. casei stimulation of IL-10 production in PBMC cultures. The IL-10 concentrations were determined in supernatant fluids from 7-day-old PBMC (106/ml) cultures stimulated with 104 to 106 S. mutans (shaded bars) (n = 6) and L. casei (open bars) (n = 4) bacteria per ml. The error bars represent 95% CIs.

FIG. 2

FIG. 2

Comparison of type 1 (IFN-γ) and type 2 (IL-4 and IL-10) cytokine mRNA in pulpal tissues from shallow and deep carious lesions. The presence of detectable cytokine mRNA in the pulps was determined using RT-PCR, and the percentage of positive pulps in the control, shallow-caries, and deep-caries groups is indicated for IFN-γ (shaded bars), IL-4 (striped bars), and IL-10 (open bars). The pulpal tissue was obtained from impacted third molars for controls (n = 16), molars with shallow caries (n = 21), and molars with deep caries (n = 25). ∗, P < 0.05.

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