Linomide-induced suppression of experimental autoimmune neuritis is associated with down-regulated macrophage functions.

Experimental autoimmune neuritis (EAN) is a T-cell mediated autoimmune disease of the peripheral nervous system, in which macrophages and T-cells feature prominently in nerve lesions. EAN represents a counterpart to Guillain-Barré syndrome in humans. In the present study, we investigated the in vitro and in vivo effects of Linomide (LS-2616, quinoline-3-carboxamide), a synthetic immunomodulatory compound, on macrophages in relation to EAN. Linomide strongly suppressed IFN-gamma and lipopolysaccharide (LPS)-induced IL-1 beta, TNF-alpha and IL-6 mRNA expression in macrophages in vitro as demonstrated by in situ hybridisation. Linomide administered daily subcutaneously from the day of inoculation completely prevented the development of clinical symptoms of EAN. Linomide administered from day 9 post immunisation (p.i.) significantly suppressed clinical EAN. Macrophages from Linomide-treated EAN rats showed decreased IL-1 beta, TNF-alpha and IL-6 mRNA expression in response to IFN-gamma and LPS. LPS-induced nitric oxide production by macrophages was also suppressed by Linomide in vitro. Linomide, however, does not affect macrophage death and release of lactate dehydrogenase. We conclude that Linomide may exert its actions in EAN and perhaps also in other autoimmune disease models, by suppressing macrophage functions.