We read with great interest the study of interactions between gold nanoparticles (GNP) and macrophages recently published by Ma et al. [1]. They observed inhibition of NO-macrophage production after successive exposure of cultured cells to lipopolysaccharides (LPSs) and GNP. Variations of other biomarkers of inflammation have confirmed their observation. This work is questionable because of a lack of information on GNP characteristics. The use of polyethylene glycol (PEG)-coated GNP (diameter: 10-15 nm) is indicated in abstract and the reference "[17]" mentioned in experimental section does not describe any PEG-coated GNP but GNP stabilized with citrate. Main GNP properties that play a role in cell interactions are size, shape, surface charge (zeta potential), solubility, and surface layer. This latter mostly influences the immediate protein coating of GNP upon contact with biological matrices. This process leads to a protein corona, creating a "molecular signature", which is recognized by immune cells and determines the route of particle internalization. PEG-coated GNP have low interaction with proteins in comparison with citrate-stabilized GNP, thus a limited uptake by cells of the reticuloendothelial system is usually observed [2]. Several recent reports in the literature describe interactions between different kinds of GNP and macrophage cell lines, using various operating conditions, expressing nanoparticle concentrations in different ways and selecting concentrations with or without indicating their relationship with cell-viability (Table 1). Even marked differences appear between these studies, most of them have concluded to an activation process.