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Using the method of reconstitution of nude mice with T cells, we examined the effects of T cell on alveolar bone resorption induced by repeated injections of Escherichia coli endotoxin into periodontal tissue. Three mice groups (normal, nude and T cell reconstituted nude mice) were used. Endotoxin derived from E coli was repeatedly injected into the gingiva of the mice left mandibles every 48 h and the mice were killed on the day after the 1st, 4th, 7th, 10th, 13th and 20th injections of endotoxin. Alveolar bone resorption was examined histopathologically and histomorphometrically. Bone surfaces in contact with the osteoclast were defined as the site of active resorption and the ratios of active resorption were compared among the 3 mice groups. Consequently, no active resorption was found after the first injection of endotoxin in any group. After the 4th injection, active resorption was found in normal mice and T cell reconstituted nude mice and gradually rose with the increase in the injection frequency. In contrast, few osteoclasts were found even after the 10th injection in the nude mice. In addition, there were statistically significant differences between the normal mice and nude mice after the 4th and 10th injections (p < 0.05). These findings suggested that T cell influences periodontal bone destruction induced by local administration of endotoxin during the early phases.
Ukai et al. (Thu,) studied this question.