Pathogenic mechanisms of apical periodontal diseases : Kinetics of dendritic cells and immure functional molecules

点击翻译按钮获取中文摘要

This study aimed to investigate the role of dendritic cells in the development of apical periodontitis. Experimental periapical lesions were induced in rat molars by making unsealed pulp exposures, and ultrastructure, distributional density and immune functional molecule expression of dendritic cells were investigated by means of inmunoelectron microscopy. During the period of active lesion expansion (expanding stage), macrophages were dominant and only a small number of dendritic cells were detected. Following lesion stabilization (chronic stage), however, most of MHC class II molecule-expressing cells were identified as dendritic cells. Cell-to-cell contact between dendritic cells and lymphocytes was sometimes seen in the chronic stage. Morphological change of dendritic cells was also noted : cells with thin and short cytoplasmic processes and poorly developed organelles were predominant in the expanding stage, whereas large cells with long cytoplasmic processes were predominant in the chronic stage. Moreover, dendritic cells in the chronic stage were divided into two subpopulations according to the immunoreactivity to CD11c and OX62 : although most dendritic cells expressed CD11c, there were minor but definite subpopulation which expressed OX62 and had a small and round cell body with a small number of short cytoplasmic processes. These findings suggested that dendritic cells, composed of different subpopulations according to the stage of maturation/activation, are involved in lesion chronicity by acting as antigen presenting cells in response to chronic antigenic challenge from infected root canals.