In the present study we show that: 1) decreased VLA-4 surface expression on circulating CD4+ and CD8+ T-cells in natalizumab treated MS patients is not explained by decreased transcriptional activity of ITGA4 and ITGB1, encoding the α4 and β1 subunits of VLA-4, or associated with decreased expression of LFA-1 integrin. This evidence concerns the gene ITGA4 and myeloid sarcoma.