Synergistic Effect of IFN-γ and TNF-α on Expression of Immune Molecules and Antigen Presentation by Schwann Cells

Neonatal rat Schwann cells were characterized with regard to their immune functions in vitro. Without stimulation they displayed low levels of ICAM-1, but not of MHC class II gene products on their surface. Expression of both immune molecules was upregulated by IFN-γ. TNF-α acted synergistically, but had no effect when given alone. ICAM-1 expression reached its maximum within 24 hr, whereas I-A plateaued only after 3 days of cytokine treatment. Increased expression of recognition molecules on Schwann cells correlated well with enhanced activation of CD4+ autoimmune T cell lines between Day 1 and 2. T cell activation was blocked by adding monoclonal antibodies directed against I-A molecules, whereas ICAM-1-specific antibodies exerted a mild costimulatory effect. We conclude that Schwann cells may exert potent immunoregulatory functions by expressing MHC and adhesion molecules, which may be further upregulated by Th1-type cytokines released by immunoinflammatory T cells in the lesion.