Two-dimensional 1H NMR studies of membrane changes during the activation of primary T lymphocytes

Two-dimensional 1H NMR spectroscopy was used to quantify the level of "mobile" plasma membrane triglyceride and the intracellular concentrations of water-soluble phospholipid precursors during the activation of both mature and immature primary T lymphocytes. The concentration of mobile triglyceride in the plasma membrane was seen to increase approximately 35-fold during 72 h of activation of murine thymic and splenic T lymphocytes with ionomycin and phorbol 12-myristate 13-acetate. This dramatic increase in mobile plasma membrane triglyceride during the activation of both mature and immature T-lymphocyte populations supports the hypothesis that immune cell activation is associated with increased plasma membrane fluidity. The intracellular concentrations of various phospholipid precursors were shown to increase during the early stages of T-lymphocyte activation and then remain at levels above those in resting cells. This may facilitate de novo phospholipid biosynthesis, which is presumably necessary since cell volume, and hence the plasma membrane surface area, was demonstrated to increase significantly during T-lymphocyte activation. Various models that might explain the origin of the NMR-visible plasma membrane triglyceride that is observed during immune cell activation and malignant transformation are examined.