THP-1/RFP cells are derived from the human monocytic THP-1 cell line by stably integration of a constitutive RFP stably expression construct. THP-1 cells are undifferentiated monocytes, but they can be induced to differentiate into macrophage-like cells upon treatment with agents such as phorbol 12-myristate 13-acetate (PMA), making them a useful model for studying the differentiation of monocytes into macrophages and their role in immune responses and inflammation. THP-1/RFP cells stably stably express RFP, can be used for in vitro assays and in vivo imaging.