Macrophages are engaged in many essential host functions, and their activation 
is a dynamic process that results in diverse functional outcomes such as the 
potentiation of bactericidal activity and production of chemokines, cytokines, 
and mediators that coordinate the inflammatory response. This pro-inflammatory 
response is bimodal, comprising a "prime" event, classically through 
interferon-γ (IFN-γ), and a "trigger," such as lipopolysaccharide (LPS). 
Recently, autophagy, which is one of the major degradative pathways in 
eukaryotic cells, has been shown to play an important role in both IFN-γ-primed 
and LPS-activated macrophages. In this study, we sought to characterize the 
mechanisms of autophagy activation in primed and activated macrophages. To this 
end, we established a macrophage RAW 264.7 cell line that expressed high levels 
of a tandem fluorescently tagged LC3 (tfLC3) autophagy marker. By using this 
macrophage cell line, autophagosome formation was observed in both IFN-γ- and 
LPS-stimulated cells. Moreover, our data demonstrated that IFN-γ, but not LPS, 
facilitated autophagosome maturation to autophagolysosomes, suggesting that 2 
distinct mechanisms regulating autophagy exist in IFN-γ-primed and LPS-activated 
macrophages.