Three-dimensional and ultrastructural ICAM-1 distribution in the choroid plexus, arachnoid membrane and dural sinus of inflammatory rats induced by LPS injection in the lateral ventricles.

To investigate immunological environment in the cerebrospinal fluid (CSF) system, ultrastructural and three-dimensional localization of intercellular adhesion molecule-1 (ICAM-1) was studied in the choroid plexus, arachnoid membrane and dural sinus of LPS-stimulated rats with immuno-SEM and TEM. The choroid plexus epithelial cells expressed rich ICAM-1 along the microvilli. The arachnoid trabeculae fibroblast-like cells demonstrated ICAM-1 expression on both sides facing the subarachnoid space moderately. The dural sinus endothelial cells, however, showed only few ICAM-1 expression and no specific localization. These results suggest that the choroid plexus and arachnoid membrane may play an important mutual role for leukocyte migration in the CSF system, and that the CSF system may function in immunoreaction independently of the vascular system with the aid of up-regulated ICAM-1 expression.