HISTOPATHOLOGICAL STUDY OF THE ROLE OF CD4-POSITIVE AND CD8-POSITIVE T-CELLS ON BONE-RESORPTION INDUCED BY ESCHERICHIA-COLI ENDOTOXIN

The purpose of this study was to clarify the involvement of CD4+ and C D8+ T cells on bone resorption induced by Escherichia coli endotoxin. Two kinds of monoclonal antibodies, anti-CD4 and/or anti-CD8, were emp loyed for the depletion of each or both T cell subsets. E. coli endoto xin was injected into mouse mesial gingiva of the first molar of the l eft mandible every 48 hours for up to 14 days (7 injections). The mice were divided into four groups: CD4-depleted, CD8-depleted, T cell-dep leted, and normal. The mice were sacrificed on the day after the 1st, 3rd, 4th, 5th, and 7th injection and alveolar bone was examined histop athologically and histomorphometrically. Bone surface in contact with osteoclasts was defined as the site of active resorption and the ratio s of active resorption were compared among the four groups. In additio n, sections obtained after the 1st, 4th, and 7th injection were immuno histologically stained in order to confirm the presence or absence of CD4+ or CD8+ T cells. Alveolar bone resorption gradually increased in normal mice as the number of injections increased. In contrast, alveol ar bone resorption was significantly weaker in each or both subset-dep leted mice. For the duration of the experimental period, the number of CD4+ T cells in CD8-depleted and normal mice significantly increased with increasing bone resorption. Considering the function of CD4+ and CD8+ T cells, these results suggest that each subset preferentially ac ts as a macrophage activator in the early period of bone resorption in duced by E. coli endotoxin.