Kinetic Study of Immunohistochemical Colocalization of Antigen-presenting Cells and Nerve Fibers in Rat Periapical Lesions

Immune and nervous systems play key roles in periapical pathosis; however, their spatial associations, which may be a prerequisite for paracrine interactions in the progression of periapical lesions, remain to be examined. In this study we examined the distribution and frequency of spatial associations between major histocompatibility complex class II molecule-expressing antigen-presenting cells (APCs) and protein gene product 9.5-immunoreactive nerve fibers in experimentally induced rat periapical lesions using double-immunofluorescence staining and confocal laser scanning microscopy. When active lesion expansion started, macrophage-like APCs frequently associated with nerve fibers around the apex. When the lesions were starting to stabilize, however, close associations between APCs with dendritic morphology and nerve fibers were found mostly in the periphery of lesions. CD86+ mature dendritic cells were also observed in this area. These findings suggest that functional interactions between APCs and nerve fibers may play some roles in the development of self-defense reactions in periapical lesions.