ABSTRACT: Objective: Achieving immunoregulation via in vivo expansion of Foxp3+ regulatory CD4+ T cells (Treg) remains challenging. Considerable efforts are being produced aiming at promoting expansion of Tregs in vitro with IL-2, rapamycin, activation with anti-CD3/CD28 mAb-coated beads or with minute foreign antigen doses, for subsequent administration to patients with autoimmune and alloimmune diseases. We have previously shown that mobilized multipotent hematopoietic progenitors (MPPs)collected in peripheral blood stem cell grafts, have the capacity to enhance Treg proliferation in vivo. Design: To analyze the possible mechanisms involved in mouse CD4+CD25high regulatory T-cells (Treg cells) expansion promoted by mobilized MPPs (MPPs), we sequenced and compared the transcriptome of activated Treg extracted from simple culture or from co-culture with MPPs. Results: Tregs cultivated with mobilized MPP had a specialized profile, with enhanced expression of sets of genes coding for receptors and transcription factors that stabilize their regulatory function particularly in inflammatory settings including CD4, CD25 (Il2ra), Foxp3, CD127low (Il7ralpha), Ctla4 high, Tnfrsf18 (Gitr) high, Ikzf2 (Helios) high, Tnfrsf4 (Ox40/CD134) high, Itgae (CD103), regulated by Satb1, Runx, Gata3. Moreover, they exhibit enhanced expression of Prdm1, recently reported to prevent methylation of Foxp3 within Tregs in central nervous system inflammation (14), and Nr4a, that stabilizes Tregs against their differentiation into effector T-cells (15). Their survival is improved by a reduced apoptosis controlled by reduced Tnfrsf1b (p75, Tnfr2) signaling pathway and FOXO-mediated transcription. Their cell cycle is arrested at the G1 stage through enhanced Cdkn1a (p21) and regulated by Runx3 and p53. conclusion: Tregs interacting with mobilized MPP are shaped, stabilized with high immunosuppressive properties.
