EXPRESSION OF A MANNOSE FUCOSE MEMBRANE LECTIN ON HUMAN DENDRITIC CELLS/

Dendritic cells (DC) are the most efficient antigen presenting cells f or T lymphocytes. CD1a CD14(-) DC with high antigen-presenting capacit ies can now be obtained easily from adherent peripheral blood monocyte s by culture in the presence of granulocyte/macrophage colony-stimulat ing factor and interleukin-4 (Sallusto et al.. J. Exp. Med. 1994, 1795 , 1109). Human macrophages express a membrane lectin. or sugar-specifi c receptor. which specifically mediates the binding and endocytosis of mannose- and fucose-terminated glycoproteins and is involved in the p hagocytosis of pathogens. A similar lectin activity was sought on cult ured human DC using flow cytometry and confocal microscopy to detect b inding and internalization of fluoresceinated neoglycoproteins [bovine serum albumin (BSA) substituted with sugar residues]. Several neoglyc oproteins especially alpha-L-fucosyl-, alpha-D-mannosyl-. N,N'-di-acet yl-beta-chitobiosyl- and beta-D-glucosyl-BSA. were endocytosed by cult ured human CD1a(-) DC as well as by CD1a(-) CD14(-) cells which were a lso obtained in the culture. Fuc-BSA and Man-BSA had the same number o f binding sires (1.7 x 10(4)/cell) on CD1a(-) DC. and hound with an af finity constant close to 10(-) l/mol. Inhibition experiments indicated that these two neoglycoproteins bound to the same membrane lectin. CD 1a(-) and CD1a(-) cells were both labeled by an antiserum specific for the human macrophage mannose receptor. The membrane lectin specific f or mannose and fucose that is evidenced in these experiments on cultur ed DC may be similar to the macrophage membrane lectin or may share fu nctional and structural properties with it.