LRRK2 and monocytic leukemia: Although the level of endogenous LRRK2 is low in resting leukocytes, upon stimulation with IFN-γ, robust up-regulation of endogenous LRRK2 has been consistently detected across various subsets of myeloid cells and lymphocytes, human peripheral blood mononuclear cell-derived CD11b+ monocytes, CD3+ T lymphocytes, CD19+ B lymphocytes [21], human primary monocyte-derived macrophages, mouse primary microglia [28], and transformed cell lines, including human THP-1 monocytic leukaemia cells [29,30], and murine RAW264.7 macrophage-like cells [21].