IL-15 MESSENGER-RNA EXPRESSION IS UP-REGULATED IN BLOOD AND CEREBROSPINAL-FLUID MONONUCLEAR-CELLS IN MULTIPLE-SCLEROSIS (MS)

IL-15, produced by monocytes and epithelial cells, is a novel cytokine with actions similar to IL-2. IL-15 induces T cell proliferation, B c ell maturation and natural killer (NK) cell cytotoxicity, and is a che moattractant for T cells, We investigated the expression of IL-15 mRNA in blood and cerebrospinal fluid (CSF) mononuclear cells (MNC) in MS, an inflammatory disease of the central nervous system where cytokines are involved. MS patients had higher numbers of IL-15 mRNA-expressing blood MNC than patients with aseptic meningo-encephalitis (AM) and he althy controls. In CSF, MS patients had even higher numbers of IL-15 m RNA-expressing cells than in blood. This discrepancy between IL-15 mRN A expression between blood and CSF MNC was not seen in AM patients. Pa tients examined during the secondary chronic-progressive phase of MS h ad higher numbers of IL-15 mRNA-expressing blood MNC compared with pat ients examined during the relapsing-remitting phase. Levels of IL-15 m RNA-positive blood MNC were similar in patients with AM, myasthenia gr avis, non-inflammatory neurological diseases and healthy controls. Tak en together these data indicate that IL-15 mRNA expression is up-regul ated in MS, further suggesting a role for proinflammatory cytokines in the pathogenesis of MS.