Proton nuclear magnetic resonance (lH-NMR) spectroscopy has been used to study immune cell activation. One-dimensional and two—dimensional 1H-NMR spectra of activated immune cells are dominated by signals arising from elevated levels of isotropically tumbling (ie., NMR-visible) mobile lipid. An increase in the level of mobile lipid compared with that seen in resting cells has been observed in a variety of activated immune cells. The appearance of the mobile lipid is associated with activation and can be induced by a variety of stimuli. However, the origin and function of the neutral lipid resonances in 1H-NMR spectra of activated immune and other cell types has been unresolved. I propose that the mobile lipids arise from phosphatidylcholine (PC) cycling
