The importance of the immune system in the pathogenesis of periodontitis is being emphasized. To investigate the effects of different immune statuses on the progression of periodontitis, we induced periodontitis in neutrophil-deficient, lymphocytedeficient, and dual neutrophil- and lymphocyte-deficient mice. The groups included BALB/c mice (Con-lym+/neu+), periodontitisinduced BALB/c and SCID mice (Peri-lym+/neu+ and Peri-lym–/neu+), and periodontitis-induced BALB/c and SCID mice treated with anti-Ly6G antibody (Peri-lym+/neu– and Peri-lym–/neu–). Periodontitis was induced by ligation of the mandibular first molar. Mice were sacrificed on days 0 (D0), 3 (D3), and 7 (D7) after ligation, and blood and periodontal tissue were analyzed. On D3, the AB area in the Peri-lym–/neu+ group was larger than in the Peri-lym+/neu+ group. The osteoclast on D3 was lower in the Peri-lym+/neu– group compared to the Peri-lym+/neu+ group. On D7, Ly6G+ cells were lower in both blood and periodontal tissue in the Peri-lym+/neu– group compared to the Peri-lym+/neu+ group, whereas CD3+ cell counts were higher only in periodontal tissue. In the Peri-lym–/neu– group, Ly6G+ cells were lower in both blood and periodontal tissue than in the Peri-lym–/ neu+ group, whereas CD3+ cells were higher in blood only. These results suggest that lymphocyte depletion delays AB loss and neutrophil depletion influences osteoclast formation at the early stage of periodontitis. In the late stage of periodontitis, lymphocyte depletion does not increase lymphocyte infiltration into periodontal tissue, even with neutrophil depletion. Collectively, different immune states may influence distinct stages of periodontitis progression.

Abstract:
INTRODUCTION
MATERIALS AND METHODS
    Animals
    Ligation-induced periodontitis and neutrophil depletion
    Flow cytometry
    Histological analyses
    Alveolar bone loss
    Osteoclast formation
    Lymphocyte and neutrophil infiltration
    Statistical analysis
RESULTS
    AB area in periodontitis-induced mice under differentimmunodeficiency conditions
    Osteoclast formation in periodontitis-induced miceunder different immunodeficiency conditions
    Lymphocytes and neutrophils in the blood and periodontaltissue of periodontitis-induced BALB/c mice with or withoutneutrophil depletion
    Lymphocytes and neutrophils in the blood and periodontaltissue of periodontitis-induced SCID mice with or withoutneutrophil depletion
DISCUSSION
ACKNOWLEDGMENTS
CONFLICT OF INTEREST
REFERENCES

• Eun-Jung Bak(Department of Oral Biology, Yonsei University College of Dentistry, Yonsei University, Seoul 03722, Korea) Corresponding author
• Ae Ri Kim(Department of Oral Biology, Yonsei University College of Dentistry, Yonsei University, Seoul 03722, Korea, BK21 FOUR Project, Yonsei University College of Dentistry, Yonsei University, Seoul 03722, Korea, Department of Biomedical science, HwaSung Medi-Science University, Hwaseong 18274, Korea)
• Min Seo Kim(Department of Oral Biology, Yonsei University College of Dentistry, Yonsei University, Seoul 03722, Korea, BK21 FOUR Project, Yonsei University College of Dentistry, Yonsei University, Seoul 03722, Korea, Department of Dentistry, The Graduate School, Yonsei University, Seoul 03722, Korea)
• Yun-Jung Yoo(Department of Oral Biology, Yonsei University College of Dentistry, Yonsei University, Seoul 03722, Korea, Department of Dentistry, The Graduate School, Yonsei University, Seoul 03722, Korea) Corresponding author