IMMUNOCOMPETENT CELLS IN RAT PERIODONTAL-LIGAMENT AND THEIR RECRUITMENT INCIDENT TO EXPERIMENTAL ORTHODONTIC TOOTH MOVEMENT

The aims of this study were to evaluate the number and distribution of immunocompetent cells in normal rat periodontal ligament (PDL) and to quantify their recruitment incident to experimental tooth movement. 2 7 young animals had the 1st right maxillary molar moved mesially by an orthodontic appliance for 1, 3, 7 and 14 days, respectively. 4 animal s served as untreated controls. An immunohistochemical procedure was c arried out on alternate serial cryostat sections, and monoclonal antib odies against CD11b (macrophages, dendritic cells), CD43 (lymphocytes, polymorphs), CD4 (helper T-lymphocytes), and class II MHC molecules w ere used. Mean counts of the immunolabeled cells in the control group showed the highest number of CD11b(+) and class II molecule expressing cells, while CD4(+) and CD43(+) cells were scarcely found. Significan t increase in the number of CD11b(+), CD43(+) cells and class II molec ules was found in the PDL of the experimentally moved Ist molars compa red with the contralateral side and the control group, while CD4(+) ce lls showed no significant increase. CD11b(+) and cells expressing clas s II molecules were found around hyalinized tissue, between dentin and cellular cementum and close to Malassez' epithelial cells. In conclus ion, normal rat PDL has high number of macrophage and dendritic-like c ells, but few lymphocytes and granulocytes. Furthermore, experimental tooth movement leads to significant recruitment of cells belonging to the mononuclear phagocytic system, but has no significant effect on th e number of lymphocytes and granulocytes in the rat PDL.