Multiple sclerosis. Evidence for antigen presentation in situ by endothelial cells and astrocytes

To investigate the possibility of local antigen presentation within the central nervous system (CNS) in multiple sclerosis (MS), frozen sections of active chronic MS lesions were stained by the peroxidase-antiperoxidase technique for the demonstration of Ia antigen using a monoclonal antibody. Ia antigen could be localized on some endothelial cells and astrocytes as well as on macrophages. While Ia+ endothelial cells were randomly distributed throughout the CNS, Ia+ astrocytes were mainly found at the edge of active chronic MS lesions. These findings in MS suggest that antigen might be presented locally within the CNS on endothelial cells, where it might lead to new lesion formation by the initiation of a local immune response; on astrocytes, where it might be involved in lesion growth at the periphery.