Identification of a novel tolerogenic cell subset in the treatment of autoimmune diseases

Abstract

Abstract We previously reported granulocyte macrophage colony-stimulating factor (GM-CSF) prevented type 1 diabetes in NOD mice through CD11c+CD8− dendritic cell (DCs) mobilization, precipitating regulatory T-cell (Treg) expansion. Furthermore, we found GM-CSF derived bone-marrow dendritic cells (G-BMDCs) can drive Treg expansion in ex-vivo CD4+splenic T-cell co-cultures through surface-bound molecule OX40L. To determine whether GM-CSF may lead to the formation of a distinct, novel CD11c+OX40L+ expressing DC subset, we generated OX40L+G-BMDCs (CD11c+OX40L+) and analyzed these cells through flow cytometry for various cell lineage markers. We determined OX40L+G-BMDCs expressed increased levels of co-stimulatory molecules CD80, CD86, PD-L1 and MHC-II in comparison to the OX40L− counterpart. Additionally, OX40L+G-BMDCs lacked expression of Ly6G, Ly6C, FceR1, surface markers indicative of granulocyte and mast cell lineage, but to our surprise, highly expressed macrophage markers F4/80, MerTK, and CD200R. To elucidate an in vivo physiological component of these OX40L+ G-BMDCs, we performed an unsupervised hierarchical clustering comparing the transcriptome of OX40L+G-BMDCs to that of all myeloid and lymphoid lineages from the Immgen database. We found that OX40L+G-BMDCs clustered most closely with macrophages and dendritic cells. Furthermore, a principal component analysis with the transcriptome of OX40L+G-BMDCs and that of macrophages and dendritic cells from the Immgen database revealed OX40L+G-BMDCs most closely clustered with macrophages. Collectively, these results suggest OX40L+ G-BMDCs may represent a distinct GM-CSF dependent, macrophage-like cell subset involved in physiological Treg homeostasis.