IL-15 is elevated in sera of patients with relapsing-remitting multiple sclerosis

Interleukin-15 is a novel cytokine produced by monocytes/macrophages and sharing several biological activities with IL-2. IL-15 induces T cell proliferation, enhances natural killer (NK) cell cytotoxicity and also stimulates B cells to proliferate and secrete immunoglobulins. The purpose of our study was to measure IL-15 levels in the serum and CSF of 21 patients with relapsing-remitting form of MS, 9 with active gadolinium enhancing lesions in MRI, 12 without enhancing MRI lesions and to compare the results with the control group. IL-15 levels were measured by ELISA. We found a significant increase of IL-15 in the sera of patients with MS in comparison with the control group consisting of 8 patients with tension headache. IL-15 serum levels were highest in patients with active, gadolinium enhancing lesions. IL-15 CSF levels were low and there was no difference between studied groups. The results may suggest the contribution of IL-15 in the immunopathogenesis of multiple sclerosis.