Scientists have shown that a process known as oxidative stress is at work during encounters between certain nanoparticles and immune cells, selectively modifying proteins on macrophages, a type of immune cell. The findings, by researchers at the Department of Energy's Pacific Northwest National Laboratory, were published in the journal ACS Nano.While oxidative stress is a common way for cell damage to occur, the findings were a surprise in some ways."Oxidative stress is occurring selectively even at low levels of exposure to nanoparticles," said Brian Thrall, a nanotoxicology expert at PNNL and a corresponding author of the study. "We've demonstrated an approach that is sensitive enough to detect effects of nanoparticles on macrophages long before those cells die. This gives us the opportunity to understand the most sensitive cellular targets of oxidative stress and the pathways involved more completely than before."This is important information for understanding how nanoparticles can alter cell function and for beginning to identify functions that allow cells to adapt versus those that are potentially involved in adverse effects," Thrall added.