Fas-mediated apoptosis in clinical remissions of relapsing experimental autoimmune encephalomyelitis

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Abstract

PLP139-51–induced experimental autoimmune encephalomyelitis (R-EAE) displays a relapsing-remitting paralytic course in female SJL mice. We investigated the role of apoptosis/activation-induced cell death (AICD) in the spontaneous recovery from acute disease. Clinical EAE was significantly enhanced in Fas (CD95/APO-1)–deficient SJL lpr/lpr mice, which displayed significantly increased mean peak clinical scores, reduced remission rates, and increased mortality when compared with their SJL +/lpr littermates. PLP139-151–specific proliferative responses were fairly equivalent in the 2 groups, but draining lymph node T cells from SJL lpr/lpr mice produced dramatically increased levels of IFN-γ. Central nervous system (CNS) Fas and FasL mRNA levels in wild-type SJL (H-2s) mice peaked just before spontaneous disease remission and gradually declined as disease remitted. We applied the terminal deoxynucleotidyl transferase–mediated dUTP nick-end labeling (TUNEL) assay to detect apoptosis in situ in spinal cords of mice at various clinical stages of EAE. Most TUNEL+ cells were found during active periods of inflammation: the acute, peak, and relapse time points. Significantly fewer apoptotic cells were observed at preclinical and remission time points. Collectively, these findings indicate that Fas-mediated apoptosis/AICD plays a major role in the spontaneous remission after the initial acute inflammatory episode and represents an important intrinsic mechanism in regulation of autoimmune responses.

Authors

Graig C. Suvannavejh, Mauro C. Dal Canto, Louis A. Matis, Stephen D. Miller