ABSTRACT: Multiple sclerosis is an immune mediated disease of the central nervous system. High-dose immunosuppression therapy followed by autologous hematopoietic stem cell transplantation (HDI/AHSCT) has emerged in the past few years as a new treatment strategy in patients with severe MS and refractory to conventional treatment. We characterized the molecular profile of T cells during immune reconstitution of these patients. Total RNA of CD4+ and CD8+ T cells from eight MS patients before transplantation and four patients at 6 months, 1 and 2 years after transplantation was processed for DNA microarray analysis. We investigated the molecular and biological function of DEG using bioinformatics tools and selected genes involved with immune response to measure quantitative gene expression by Real-time PCR. In CD8+ T cells, we measured the levels of expression of 23 genes modulated after transplantation: nine transcriptional factors (LEF1, FOXD1, CEBPD, JUN, JUNB, RELB, IFI16, AEBP1) including the translational factor PDCD4, the chemokine CCR7 and adhesion molecule L Selectin, three TNF superfamily members (TNFRSF4, TNFRSF19L, LT?), seven genes involved with molecular signaling (SOCS1, SOCS3, DGKH, CSNK1L1, IKB?, IKB?, IKB?), and the immune cell receptors CD47 and SIRPG. In CD4+ T cells, we evaluated the relative level of expression of STAT3, FcRL3, PDCD1, DGKH, CSNK1L1, L Selectin, CCR7 and PIAS3 that were all modulated after transplantation. We found significantly transcriptional changes in both T cells subsets during the first 2 years post-transplantation, but the analysis of CD8+ T cells revealed more extensive changes of genes involved in effector immune responses. In order to study the transcriptional changes in T cell subsets from MS patients submitted HID/HSCT, immunomagnetically purified CD4+ and CD8+ T-cells from the peripheral blood of 8 patients before transplantation and 4 patients 6 months, 1 year and 2 years after tranplantation, as well as from 4 healthy controls were isolated and processed the microarray assay according Agilent's protocol. The differential expressed genes, molecular characterization and networks analysis were evaluated using robust bioinformatic tools, then the real time PCR was done to validate the 27 immune related-genes.