Résumé : In this Data in Brief, we have provided data describing the secretion profile of two main immunoregulatory proteins, heme oxygenase-1 (HO-1) and CD200, from bone marrow (BM), Wharton׳s Jelly (WJ) or adipose tissue (AT) mesenchymal stromal cells (MSCs) being cultivated either in the absence or presence of activated T-cells. Whilst HO-1 is a stress-responsive enzyme displaying diverse cytoprotective effects, CD200 is a membrane glycoprotein delivering immunoregulatory signals following interaction with its receptor (CD200R). Using Enzyme-linked immunosorbent assay (ELISA) techniques, these data are presented to show distinct constitutive secretion of both HO-1 and CD200 depending on MSC types. The data presented also demonstrate that the protein levels of HO-1 and CD200 are differentially modulated during co-culture with activated T-cells. All assays were carried out in triplicates and the mean values are reported. The data presented in this article are complementary to our previously published report entitled "The Immunomodulatory Potential of Mesenchymal Stromal Cells: A Story of a Regulatory Network." [1].