CSF2 and myeloid sarcoma: Interestingly, a recent study in which Hafler and colleagues cloned single myelin-reactive T cells from MS patients and healthy donors also determined that many IFN-γ+ clones also produced GM-CSF, and most IL-17-producing clones from MS patients co-expressed GM-CSF – yet many T cell clones derived from MS patients that produced high levels of GM-CSF expressed neither IFN-γ nor IL-17 (10).