MACROPHAGE INHIBITION OF LYMPHOCYTE AND TUMOR-CELL GROWTH IS MEDIATEDBY 25-HYDROXYCHOLESTEROL IN THE CELL-MEMBRANE

We have previously reported that a lipid molecule in the membrane frac tion of cloned macrophage hybridomas inhibited the growth of lymphocyt es and several tumor cell lines. In this study, the inhibitory lipid m olecule in the membrane fraction of macrophages was analyzed by thin-l ayer chromatography and identified as 25-hydroxycholesterol, a family of oxysterols. This conclusion was confirmed by analysis using gas chr omatography-mass spectrometry. In addition, both 25-hydroxycholesterol and the lipid molecule recovered from macrophage cell membrane induce d apoptosis of the murine T cell lymphoma, BW-5147. These results sugg est that an oxysterol expressed in the macrophage cell membrane may pa rticipate in the regulation of cell growth through cell contact.