Direct injection of cytokines into the spinal cord causes autoimmune encephalomyelitis-like inflammation

A single micro-injection of Tumour Necrosis Factor alpha (TNF) or gamma Interferon (IFN-gamma) into the lumbosacral spinal cord of the rat produced meningitis and mononuclear cuffs within the cord, an inflammatory response remarkably similar in pattern to that observed during experimental autoimmune encephalomyelitis (EAE), a research analog of multiple sclerosis. Rats injected with saline or heat-inactivated cytokine exhibited no such inflammatory response. In other experiments, the accumulation of radiolabeled spleen cells into spinal cord was measured after the injection of various doses of TNF and IFN-gamma, results indicated that both cytokines elicited accumulation of spleen cells in an additive but not synergistic manner. Potentially, the direct injection model offers a new and simplified way of examining mechanisms of early inflammation in the central nervous system, without the need for immunisation with neuroantigen or passive transfer of sensitised cells.