AN NMR INVESTIGATION OF THE CHANGES IN PLASMA-MEMBRANE TRIGLYCERIDE AND PHOSPHOLIPID PRECURSORS DURING THE ACTIVATION OF LYMPHOCYTES-T

Two-dimensional H-1-NMR spectroscopy was used to quantify the level of isotropically tumbling plasma membrane triglyceride and the intracellular concentrations of water-soluble phospholipid precursors during the activation of thymic T-lymphocytes. The concentration of "mobile" triglyceride in the plasma membrane was seen to increase 25-fold during 72 h of activation of murine thymic T-lymphocytes with ionomycin and phorbol myristate acetate. This is the first unequivocal demonstration of such a dramatic increase in mobile plasma membrane triglyceride during T-lymphocyte activation and leads to the suggestion that immune cell activation is associated with increased plasma membrane fluidity. The intracellular concentrations of choline- and ethanolamine-based 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 thymocyte activation.