Following an exhaustive literature review on the global issue of intracerebral presentation of antigen, this monograph summarizes results from voluminous work to establish which indigenous cerebral cells might present (auto)antigen to the immune system and thus initiate an (auto)immune reaction. Employing the combination of (a) a lesion model in which neuronal degeneration and neuronophagia are caused without disruption of the blood—brain barrier, (b) stable labeling of the neuronophages via phagocytosis of the permanent nontoxic fluorescent marker Fluoro-Gold from preloaded neurons, and (c) immunocyhemical identification of all FG-labeled brain neuronophages, the authors provide evidence that the only cells in the rat CNS which can be regarded as the resident antigen presenting cells of the brain are perivascular cells.