Granulocyte-macrophage colony-stimulating factor （GM-CSF）, which belongs to the colony-stimulating factor （CSF） superfamily and was originally identified as a hemopoietic growth factor, is mainly produced by lymphocytes and innate lymphoid cells. During inflammation, GM-CSF is principally produced by T helper （Th） cells and acts as a communication conduit between myeloid cells and tissue-invading lymphocytes. GM-CSF increased Treg numbers and its immunoregulatory activities that led directly to dopaminergic neuronal protection in the substantia nigra and striatum