Interferon-beta treatment of experimental autoimmune encephalomyelitis leads to rapid nonapoptotic termination of T cell infiltration.

We investigated the possible mechanisms how interferon (IFN)-beta may control T cell infiltration in the CNS in experimental autoimmune encephalomyelitis (EAE). Adoptive transfer (AT) EAE was induced in groups of six female Lewis rats. Animals were treated with 3 x 10(5) units of recombinant rat IFN-beta s.c. once at 18 hr, or with 10 mg/kg methylprednisolone (MP) i.v. twice at 18 and 6 hr prior to dissection, or with a combination of both. T cell apoptosis was detected by immunohistochemistry on paraffin sections of spinal cord, using morphological criteria and TUNEL staining. Double labeling of immune cells was done for tumor necrosis factor (TNF)-alpha and metalloproteinase (MMP) 2. Disruption of the blood-brain barrier (BBB) was visualized by staining for albumin. In severe EAE, an increase of T cell apoptosis was seen after IFN-beta alone (all data presented as mean +/- SD: 24.5% +/- 2.2%, P < 0.05, vs. 19.4% +/- 3.1% in controls), and in combination with MP (29.4% +/- 7.3%, P < 0.05 vs. controls). Only the combination therapy decreased T cell infiltration (53.9 +/- 17.7 cells/mm(2), P < 0.05, vs. 99.5 +/- 35.2 cells/mm2 in controls). In moderate EAE, the rate of T cell apoptosis was slightly increased after IFN-beta (21.2% +/- 5.2% vs. 17.4% +/- 5.0% in controls), whereas MP alone (25.5% +/- 3.5%, P < 0.01 vs. controls) and the combination therapy (22.4% +/- 4.8%, P < 0.05 vs. controls) had a clear augmenting effect. IFN-beta tended to decrease T cell infiltration (46.1 +/- 12.7 cells/mm2) compared to controls (59.2 +/- 18.5 cells/mm2). The rate of TNF-alpha-expressing T cells was significantly decreased by IFN-beta and in combination with MP. Also, TNF-alpha expression in macrophages was significantly reduced by IFN-beta and by the combination therapy. The rate of MMP2-expressing macrophages was lower after IFN-beta but clearly decreased only in combination with MP. BBB disruption was ameliorated after IFN-beta but significantly only in combination with MP. Our study indicates that IFN-beta affects the immunopathological process in EAE in several ways, but apoptosis appears as a minor component. In view of treatment of MS relapses, the synergistic effects in this study corroborate the use of a combination therapy with high-dose MP and IFN-beta.