The results suggest that the MS-protective haplotype is associated with increased IL7Rα expression, especially of the membrane-bound isoform, in monocytes and dendritic cells (Hap 2), that the cytokine IFNβ increases IL7Rα expression in these cells, and that absence of this IFNβ-responsiveness in dendritic cells is associated with the highest MS risk (Hap 4 homozygotes). This evidence concerns the gene IFNB1 and myeloid sarcoma.