Requirement of B7 Costimulation for Th1-Mediated Inflammatory Bone Resorption in Experimental Periodontal Disease

Abstract

The CD28 costimulation at TCR signaling plays a pivotal role in the regulation of the T cell response. To elucidate the role of T cells in periodontal disease, a system of cell transfer with TCR/CD28-dependent Th1 or Th2 clones was developed in rats. Gingival injection of specific Ag, Actinobacillus actinomycetemcomitans 29-kDa outer membrane protein, and LPS could induce local bone resorption 10 days after the transfer of Ag-specific Th1 clone cells, but not after transfer of Th2 clone cells. Interestingly, the presence of LPS was required not only for the induction of bone resorption but also for Ag-specific IgG2a production. LPS injection elicited the induction of expression of both B7-1 and B7-2 expression on gingival macrophages, which otherwise expressed only MHC class II when animals were injected with Ag alone. The expression of B7 molecules was observed for up to 3 days, which corresponded to the duration of retention of T clone cells in gingival tissues. Either local or systemic administration of CTLA4Ig, a functional antagonist of CD28 binding to B7, could abrogate the bone resorption induced by Th1 clone cells combined with gingival challenge with both Ag and LPS. These results suggest that local Ag-specific activation of Th1-type T cells by B7 costimulation appeared to trigger inflammatory bone resorption, whereas inhibition of B7 expression by CTLA4Ig might be a therapeutic approach for intervention with inflammatory bone resorption.

B and T Lymphocytes Are the Primary Sources of RANKL in the Bone Resorptive Lesion of Periodontal Disease

“…Differentiated osteoclasts were identified as tartrate-resistant acid phosphatase (TRAP)-positive cells with three or more nuclei as described previously. 30 The TRAP ϩ cells with more than three nuclei were counted as osteoclasts using phase contrast microscopy and expressed as cell number/well of 96-well plates. The bone resorption activity of osteoclasts was evaluated by a pit formation assay using a calcium phosphate-coated tissue culture vessel system (Biocoat Osteologic System; BD Biosciences, San Jose, CA) or dentin disks (Alpco Diagnostics, Windham, NH) according to the manufacturers' instructions.…”

“…Our rat periodontal disease model also illustrated that antigen-specific T-cell and B-cell activation in the inflamed gingival tissues is necessary for the induction of periodontal bone loss, and simple inflammation induced by lipopolysaccharide alone does not cause periodontal bone resorption. 22,30 Therefore RANKL expression by activated lymphocytes may be a prerequisite to develop osteoclast differentiation in the gingival tissues having pre-existing inflammation.…”

T Cell Response Mediated by Myeloid Cell-Derived IL-12 Is Responsible for Porphyromonas gingivalis-Induced Periodontitis in IL-10-Deficient Mice

“…On day 0, animals were sacrificed and submandibular lymph nodes were isolated. T cells were enriched by passing cells through a glass wool and nylon wool column as previously described (28). Adherent splenic APC were isolated from MP/PMN-specific Stat3-deficient and Stat3 flox/flox mice, and treated with mitomycin C (MMC) as previously described (29).…”

The Role of Distinct T Cell Subsets in Periodontitis—Studies from Humans and Rodent Models

“…In addition, the injection of IFN-γ into the mice further enhanced the bone loss [10]. Furthermore, adoptive transfer of antigen-specific Th1 cells but not Th2 cells enhanced alveolar bone destruction in rats injected with the A. actinomycetemcomitans 29-kDa outer membrane protein and lipopolysaccharide (LPS) into gingiva [11]. In contrast, a pathogenic role of the Th2 response was proposed in a study demonstrating that Tannerella forsythiainduced alveolar bone loss was accompanied by an increase in IL-5 but not of IFN-γ or IL-17 [12].…”

“…Immunohistologic analysis showed only a small number of CTLA-4 + cells in periodontitis lesions and healthy sites [74,75]. In rats, administration of CTLA4-immunoglobulin fusion proteins (CTLA4Ig) abrogated the alveolar bone resorption that was induced by gingival injection of A. actinomycetemcomitansderived antigens, suggesting a protective role of CTLA-4 in periodontitis [11]. Anti-inflammatory cytokines are an additional mechanism through which regulatory T cells control inflammation.…”