A LEUKOCYTE LIPID UP-REGULATES THE AVIDITY OF LYMPHOCYTE FUNCTION-ASSOCIATED ANTIGEN-1

An acidic lipid termed leukocyte adhesion lipid (LAL) was isolated fro m PMA stimulated lymphoid and myeloid cell lines HL60, Jurkat, K562 an d U937 but not from unstimulated cells or PMA treated Cos7 cells. LAL treated peripheral blood leukocytes (PBL) adhered strongly to IL-1 bet a activated human umbilical vein endothelial cells (HUVEC), and the in teraction could be inhibited by antibodies to intercellular adhesion m olecule (ICAM-1) or lymphocyte function-associated antigen-1 (LFA-1). Leukocytes treated with LAL maintained the high avidity state of LFA-1 for at least 1 hr whereas the avidity of LFA-1 in PMA treated cells d eclined after 30 min. LAL was stable to heat (100 degrees C, 10 min), alkaline phosphatase and proteinase K treatments. Chemical analysis su ggested that LAL contained unsaturated lipids. Our findings provide ev idence for the involvement of lipids in LFA-1 activation. (C) 1994 Aca demic Press, Inc.