Interleukin-10 (IL-10)-producing B cells (B10 cells) play a critical role in the immune system balance by negatively regulating inflammatory responses. This study was conducted to determine the effect of local B10 cell induction on periodontal inflammation and bone loss in ligature-induced experimental periodontitis in vivo. Purified spleen B cells from C57BL/6J mice (8 to 10 weeks old) were cultured with CD40 ligand (CD40L) and the Toll-like receptor 9 (TLR9) agonist cytidinephosphate- guanosine oligodeoxynucleotide (CpG) to determine effective IL-10 induction in vitro. Silk ligatures (size 7-0) were tied around the mouse maxillary second molars on day 0, followed by the injection of CD40L and CpG into the palatal gingiva on days 3, 6, and 9. All the mice were sacrificed, and samples were collected on day 14. CD40L and CpG significantly increased the level of IL-10 production by B cells in vitro, although the frequencies of CD1(dhi) CD5 (+) and IL-10-producing (IL-10 (+)) CD45 (+) cells were decreased. IL-10 was predominantly produced by the CD1(dhi) CD5 (+) subpopulation of B cells. In vivo, both IL-10 mRNA expression and the number of IL-10 (+) CD45 (+) cells were significantly increased after gingival injection of CD40L and CpG. Periodontal bone loss was significantly decreased and the gingival expression of IL-1 (+), tumor necrosis factor alpha, and RANKL was significantly reduced. The number of multinucleated tartrate-resistant acid phosphatase-positive cells along the alveolar bone surface was significantly decreased after gingival injection of CD40L and CpG. This study indicates for the first time that the local induction of B10 cell activity could inhibit periodontal inflammation and bone loss.