IFN-γ plus M-CSF promotes a similar differentiation phenotype to that observed using pharmacologic stimuli. (a). THP-1 cells were either left untreated (upper panel) or treated with 500 U/ml IFN-γ plus 5 ng/ml M-CSF (middle panel) or 50 nM PMA (lower panel) for 48 hours. Subsequently, the cells were photographed using a Nikon Diaphot Camera set up and Axon Imaging Workbench software. Magnification is at 40 ×. (b). THP-1 cells were either left untreated or treated for 48 hours with either 50 nM PMA (PMA) or 500 U/ml IFN-γ plus 5 ng/ml M-CSF (I+M) as indicated. Subsequently, these cells were stained with antibodies to macrophage markers CD36 (upper panel), CD11b (middle panel) and CD68 (lower panel) and then analyzed by flow cytometry.