CHARACTERIZATION OF THE INTERACTION OF GALACTOSE-EXPOSING PARTICLES WITH RAT KUPFFER CELLS

The characteristics of the recognition system involved in the binding of galactose-exposing particles to freshly isolated rat Kupffer cells were determined. For this purpose we used iodinated lactosylated low-d ensity lipoprotein (I-125-Lac-LDL) as a ligand for the galactose recep tor on Kupffer cells. The affinity of the binding of I-125-Lac-LDL to Kupffer cells was saturable (23 500 galactose-specific binding sites p er cell) and of high affinity (2.4 +/- 0.3 nM). The order of potency o f various carbohydrates in inhibiting the association of I-125-Lac-LDL with Kupffer cells was as follows: N-acetylgalactosamine > L-fucose > > N-acetylglucosamine/mannan. Association of I-125-Lac-LDL With Kupffe r cells in the absence of Ca2+ was at the same level as in the presenc e of 50 mM N-acetylgalactosamine. A polyclonal antibody raised against the rat asialoglycoprotein receptor inhibited the binding of I-125-La c-LDL to Kupffer cells and reacted in a Western blot with two proteins (molecular mass 88 and 77 kDa), which correspond to the molecular mas s of the fucose receptor [Lehrman, Haltiwanger and Hill (1986) J. Biol . Chem. 261, 7426-7432]. Furthermore, the ability of fucosylated neogl ycoproteins to displace I-125-Lac-LDL from Kupffer cells was equally d ependent on the extent of fucosylation as previously reported for the fucose receptor. We conclude that the fucose receptor and not the C-re active protein, as recently proposed [Kempka, Roos and Kolb-Bachofen ( 1990) J. Immunol. 144, 1004-1009], functions as the galactose-particle receptor on the Kupffer cell. The binding of galactose-exposing parti cles to the fucose receptor is a previously unknown property of this r eceptor.