We analyzed the proteomic profile of purified immune-cell subsets, i.e. CD4+ and CD8+ T cells, from genotyped relapsing–remitting MS (RRMS) patients and healthy controls, which allows us to disentangle potential cell-subtype specific differences that could not be detected in a heterogeneous cell material, permitting a comprehensive understanding of disease mechanisms of MS. This evidence concerns the gene CD4 and myeloid sarcoma.