Chronic Permeability of the Central Nervous System to Mononuclear Cells in Experimental Allergic Encephalomyelitis in the Lewis Rat

Abstract

In order to assess whether experimental allergic encephalomyelitis (EAE), a putative animal model for multiple sclerosis (MS), is an ongoing chronic disorder, we have studied the permeability of spinal cords of Lewis rats with EAE to ³H-uridine- or ³H-thymidine-labeled lymphoid cells obtained from thymuses of naive donors or from draining lymph nodes of donors injected with guinea pig spinal cord + complete Freund's adjuvant (CFA), guinea pig myelin basic protein + CFA, or with CFA alone. During the acute clinical phase of EAE there is a high-level infiltration of ³H-thymidine- or ³H-uridinelabeled cells into the spinal cords. After clinical recovery from EAE up to 58 days post-inoculation, there is a lowlevel infiltration of ³H-thymidine-labeled cells into the spinal cords. A similar infiltration into the spinal cords by ³H-uridine-labeled cells was not detected. Donor cells from animals immunized with CFA alone showed similar levels of infiltration into the spinal cords of animals with EAE as donor cells from animals immunized with the encephalitogenic emulsion. Spinal cords from recipients immunized with CFA alone showed no increased permeability to labeled cells. Heat-killed labeled cells did not migrate into the spinal cords of animals with EAE. We conclude that a) EAE is a chronic disease and in this regard is a valid model for MS; and b) in the chronic phase of EAE, recently divided cells (³H-thymidine-labeled cells) show higher levels of migration into the target tissue than ³H-uridine-labeled cells.