['Infiltrating T-helper cells, cytotoxic T-cells, B-cells and monocytes are thought to mediate the damage to myelin, oligodendrocytes and axons in multiple sclerosis (MS), which results in progressive disability.', 'The objective of this paper is to explore gene expression profiles of leukocytes in the cerebrospinal fluid (CSF) compartment of MS patients during relapse.', 'Global gene expression was analyzed by DNA microarray analysis of cells in CSF from MS patients and controls, and verifications were performed with real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA).', 'Fifty percent of the recently described risk genes for MS and 28% of non-risk genes were differently expressed in MS patients compared to controls (χ(2)-test, p=7.7 × 10(-5)). Genes involved in T- and NK-cell processes were up-regulated, and genes involved in processes targeting innate immunity or B-cells were down-regulated in MS. Increased expression of EDN1 and CXCL11 and decreased expression of HMOX1 was verified with real-time PCR and increased expression of CXCL13 was verified with ELISA in CSF.'] Are mS risk genes transcriptionally regulated in CSF leukocytes at relapse?