ALPHA-3-FUCOSYLTRANSFERASES AND THEIR GLYCOCONJUGATE ANTIGEN PRODUCTSIN THE DEVELOPING HUMAN KIDNEY

BACKGROUND: Three patterns of alpha-3-fucosyltransferase activity have been described in human adult tissues with different acceptor specifi city: myeloid, plasma and Lewis (25). Five- to ten-week embryos expres s the myeloid enzyme in all tissues tested, then this enzyme is replac ed by plasma or Lewis enzymes, with the exception of leukocytes that c ontinue to express the myeloid form of the enzyme in the adult (29). T hese enzymes have not been studied as yet in the developing human kidn ey. EXPERIMENTAL DESIGN: The three different alpha-3-fucosyltransferas es were studied in homogenates of mesonephros and metanephros with syn thetic oligosaccharide acceptors. The oligosaccharide precursors and p roducts of these enzymes (precursor, H, Le(a), sialyl-Le(a) and Le(b) for type 1 and precursor, H, Le(x), sialyl-Le(x) and Le(y) for type 2) were localized by immunofluorescence with specific antibodies. RESULT S: Only the myeloid alpha-3-fucosyltransferase is detected at 5 weeks in mesonephros and it disappears at 8 weeks. In metanephros, the myelo id enzyme alone is detected between weeks 6 and 8. The plasma enzyme t hen appears and only at the last trimester of gestation does the Lewis enzyme appear. Three histologic patterns that are concordant with the expression of the alpha-3-fucosyltransferases are observed: I. Induce r, S-shaped body, Bellini and calyce express Le(x) at an early stage w hen, only the myeloid alpha-3-fucosyltransferase is detected; II. Late r, the proximal tubules and descending limbs of Henle's loop express L e(x) (week 9) and sialyl-Le(x) (week 16) when the plasma alpha-3-fucos yltransferase appears; III. Calyceal and collecting systems always exp ress Le(x) and after week 12 Le(a) and Le(b) appear, in accordance wit h the late appearance of Lewis alpha-3/4-fucosyltransferase. CONCLUSIO NS: The sequential appearance of enzymes and their products suggests t hat during renal organogenesis the myeloid alpha-3-fucosyltransferase is progressively replaced by the plasma enzyme in the proximal tubules and later by the Lewis enzyme in Bellini's ducts and calyce.