T he proinflammatory response of macrophages to stimuli, such as lipopolysaccharide (LPS) or IFN , can be blocked by ligands for peroxisome proliferator-activated receptors (PPARs). However, the mechanisms, and even the validity, of this antiinflammatory role for PPARs has recently come under question. The paper by Welch et al. (1) in this issue of PNAS addresses some of these concerns, and sug...
