IL6 and myeloid sarcoma: Granulocyte-macrophages colony-stimulating factor (GM-CSF) and interleukin (IL)-6 are critical for the induction of MDSCs during emergency myelopoiesis,9 and necessary for MDSC differentiation from bone marrow cells.13 Additionally, our previous study showed that prostaglandin (PG)E2, besides GM-CSF and IL-6, provides a critical signal for the activation of tolerogenic functions of human MDSCs,14 increases their resistance to pro-inflammatory stimuli, and potentiates their capacity to induce non-conventional regulatory T cell (Treg) subsets, all of which could be beneficial for MS therapy.