Experimental study of the effect of T cell on alveolar bone resorption induced by bacterial endotoxin

牙周病是由细菌感染和局部免疫细胞对细菌的侵袭引起的。这些细胞分泌细胞因子，据报道，这些细胞因子不仅是免疫反应的调节物质，也是组织破坏的媒介。事实上，已有许多报道表明免疫反应的介体T细胞分泌的某些细胞因子与牙槽骨吸收有关。然而，T细胞是否真的与牙周组织破坏有关尚不清楚。因此，在第一项研究中，研究了正常小鼠、T细胞缺陷裸鼠和先天缺乏T细胞和B细胞的SCID小鼠每48h注射一次大肠杆菌内毒素所引起的牙槽骨吸收。此外，本研究还使用了由抗CD4和/或抗CD8单抗引起的CD4和/或CD8耗竭小鼠。正常小鼠注射4次后即可观察到牙槽骨吸收，裸鼠注射7次，SCID小鼠注射10次后即可观察到牙槽骨吸收。T细胞耗竭的小鼠，尤其是CD_4耗竭的小鼠，也表现出较弱和延迟的骨吸收。这些发现有力地提示了T细胞与骨吸收的关系。因此，在第二次实验中，建立了转移T细胞的小鼠，并注射了与第一次实验相同的内毒素。注射4次后，这些小鼠表现出与正常小鼠相似的微弱但明显的骨吸收。基于这些结果，T细胞与内毒素诱导的骨吸收密切相关，T细胞产生细胞因子的研究有待进一步研究。

Periodontal disease are caused by bacterial infection and some immune cells locally infiltrated against it. There cells secrete cytokines which have been reported to act not only as regulatory substances for immune responses, but mediators of tissue destruction. In fact, there have been many reports which suggest the relation between some cytokines secreted from T cell, a mediator of immune responses, and alveolar bone resorption. However, it has been unclear that T cells truly relate with periodontal tissue destruction. So in first study, alveolar bone resorption induced by every 48 h injections of E.coli endotoxin was investigated in normal mice, T cell deficient nude mice and SCID mice congenitally lacking both T and B cells. In addition, CD4 and/or CD8 depleted mice by the administration of anti-CD4 and/or anti-CD8 monoclonal antibodies were used in this study. In normal mice, alveolar bone resorption was observed after 4 times injection, and after 7 times in nude mice and 10 times in SCID mice. T cell depleted mice, especially CD4 depleted mice, also revealed the weaker and delayd bone resorption. These findings strongly suggested the relation between T cells and bone resorption. So in second experiment, mice transfered with T cells were established and injected with endotoxin as same as in first study. After 4 times injection, these mice showed the weak but obvious bone resorption similarly in normal mice. Based on these results, T cells closely related the bone resorption induced by endotoxin and further study should be investigated on cytokine production by T cells.