|
Experimental allergic encephalomyelitis (EAE) is a demyelinating
diseasethat characterized by perivascular inflammatory lesions
in central nervoussystem. Murine EAE can be induced by an
active immunization with myelin basic protein(MBP) in complete
Freund's adjuvant(CFA) and Bordetella pertussiscoadjuvant in
susceptible strains of mice. Three commonly used susceptible
strains are SJL/J (H-2s), PL/J (H-2u), andB10.PL (H-2u), while
resistant strains are C57BL/6 (H-2b), AKR (H-2k), and BALB/c
(H-2d), etc. However, we foundthat another intraperitoneal(i.
p.) MBP/CFA and intracerebral (i.c.) MBP restimulation in
addition to the standard protocol would induce EAE in resistant
C57BL/6 mice. Clinical symptoms would develop 2 days after the
i.c. injection. The histopathological observation manifested
cellular infiltration by leukocytes in perivascular spaces,
cerebral cortex and spinal cord. The neutrophils were prominent
at 12 h after i.c. injection, then were replaced by mononuclear
cells 24 h later. Cervical lymph nodes serves as a connection
between the brain and the peripheral immune system. The
cervical lymphatics had dynamic changes during the development
of EAE with regard to the the cell number between cervical and
distal lymph node cells. The cells derived from cervical lymph
nodes had higher MBP-stimulated proliferation than that of
distal lymph nodes. An unusual lymphocyte subset with CD4-CD8-
CD3+Vb8+ phenotype was found either in cervical lymph nodes or
in brain. These cells can be enriched after in vitro culture,
together with the upregulation of TCR Vb8. Using b-
galactosidase expressing E. coli as tracer, X-gal staining
showed that the blood-brain barrier was opened at 6 h after i.c.
challenge. The ICAM-1 and VCAM-1 adhesion molecules that
mediate the migration of leukocytes increased after i.p. or i.c.
restimulation. Interestingly, FasL as well as Fas expressionwas
also found on the inflammatory brain, and apoptotic cells were
detected by in situ hybridization. Furthermore, the kinetic
analysis of cytokine expression was done by RT-PCR and
immunohistochemistry. In the early phase of EAE, the cytokine
profiles in brain showed an so-called Th0 type. The predominant
Th1 pattern was accompanied with active disease. IL-10 was the
only cytokine remaining high expression during the recovery of
EAE. The immunoreactivity of anti- IFN-g and IL-4 mAb were
mainly observed on endothelial cells, while the infiltrated
cells showed high immunoreactivity of anti-IL-12 mAb. Taken
together, we hypothesize that the i.p. stimulation reactivates
the autoreactive T cells. The i.c. injection of MBP might have
changed the permeability of blood- brain barrier and enhanced
ICAM-1 and VCAM-1 expressions on cerebral endothelium.
Theseevents resulted in inflammatory cell infiltration including
autoreactiveT cells and the development of EAE. Besides, CD4-
CD8-CD3+, apoptosisof infiltrated cells and the Th1/Th2
interactions might also be involvedin the regulation of EAE.
|