Lipoproteins, chylomicrons (Ch?), very low density lipoprotein (VLDL), low
density lipoprotein (LDL), high density lipoprotein (HDL) and acetyl modifi
ed LDL (AcLDL) can stimulate natural killer (NK) cells upon binding to spec
ific receptors. Using flow cytometry and a specific monoclonal antibody aga
inst phosphotyrosine, we assessed the effect of lipoproteins on total intra
cellular expression of immunoreactive phosphotyrosine. Tyrosine phosphoryla
tion increased when lipoproteins were added to purified NK cells, previousl
y cultured overnight in RMPI-0.5% fatty acid free bovine serum albumin. The
optimal effect occurred at 15 minutes for all the lipoproteins used. The c
oncentrations of lipoprotein were 10 mu g of protein/ml of CM, and 20 mu g
of protein/ml for the other lipoproteins. The effect of lipoproteins on pho
sphotyrosine positivity was as follows: LDL > VLDL > CM > HDL > AcLDL. Thus
lipoproteins may activate NK cells through tyrosine phosphorylation and th
is signal transduction pathway seems to be enhanced when these cells are ac
tivated with LDL. Med Sci Res 26:795-797. (C) 1998 Lippincott Williams & Wi
lkins.