SUMMARYBrain inflammation and paraplegia can be induced by an additional intraperitoneal (i.p.) and intracerebral (i.c.) restimulation in B6 mice after standard immunization with MBP in Freund's complete adjuvant (FCA) and Bordetella pertussis coadjuvant. Only the combination of i.p. MBP/ FCA and i.c. MBP injection could induce clinical paraplegia; either one alone was not effective. Clinical symptoms would develop 2 days after the i.c. injection. The induction of paraplegia was MBP-specific, as irrelevant bovine serum albumin with the same protocol could not induce it. The i.p. restimulation was requisite and needed the MBP in FCA, as MBP in PBS was ineffective. Histopathological observation manifested cellular infiltration by leucocytes in perivascular spaces and cerebral cortex. Neutrophils were prominent at 12 h after i.c. injection, then were replaced by mononuclear cells 24 h later. There were dynamic changes in cell number and immunophenotype of VLA-4 þ expression in cervical lymph node cells after i.c. injection. The cells derived from cervical lymph nodes had higher MBP-stimulated proliferation than that of distal lymph nodes. This additional i.p. and i.c. stimulation provides a new manipulation to study brain inflammation.

We previously reported that murine experimental allergic encephalomyelitis can be induced by an additional intraperitoneal and intracerebral (i.c.) restimulation in resistant B6 mice after standard immunization with myelin antigens in complete Freund's adjuvant and Bordetella pertussis coadjuvant. Neutrophils infiltrated into perivascular spaces at 12 h, followed by mononuclear cells 24 h after i.c. injection. In this study, we report that the i.c. injection induced the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). The kinetic expression of ICAM-1 or VCAM-1 on brain endothelial cells paralleled the infiltration of neutrophils and mononuclear cells, respectively. The infiltrated lymphocytes also expressed very late antigen-4 (VLA-4) molecules. The microvascular endothelial cells were positive for VCAM-1, whereas the surrounding mononuclear cells were VLA-4 positive. Furthermore, we found a unique subpopulation of cells with characteristics of CD4(-)CD8(-)V(beta)8(+) markers. The kinetic studies of this population showed that these cells were transiently depleted from 12 to 24 h after i.c. challenge (before the development of clinical symptoms) in cervical lymph nodes. These CD4(-)CD8(-)V(beta)8(+) cells can be expanded by in vitro culture with myelin basic protein or IL-2. No significant changes of CD4(+)/CD8(+) cells were noted. CD4(+)CD8(-)CD3(+) cells were also found in brain by double histochemical stains and were the major infiltrating cells at 24 or 48 h after i.c. challenge.