Glycobiology, Vol 8, 1215-1220, Copyright © 1998 by Society for Glycobiology
J Keusch, PM Lydyard and PJ Delves
An absence of galactose on the N-linked oligosaccharides of immunoglobulin
G (IgG) has been shown to affect the functional activity of the antibody
molecule. In patients with rheumatoid arthritis there is an increased
proportion of IgG which lacks galactose and correspondingly lower levels of
beta1, 4-galactosyltransferase (beta4Gal-T) activity. The recent
demonstration of several expressed beta4Gal-T genes in man raises the
possibility that the enzyme responsible for the decreased IgG galactose is
not the "classical" beta4Gal-T (beta4Gal-T1). To directly address the
question of whether reduced beta4Gal-T1 would lead to reduced IgG
galactose, the level of beta4Gal-T1 in a human IgG-secreting B cell line
was specifically altered using stable transfection with sense
(SpcDNA3-Gal-T1) or antisense (ASpcDNA3-Gal-T1) human beta4Gal-T1 cDNA.
SpcDNA3-Gal-T1 B cell transfectants expressed up to a 2.5-fold higher level
of beta4Gal- T enzyme activity for the exogenous neoglycoconjugate acceptor
GlcNAc- pITC-BSA than did ASpcDNA3-Gal-T1 transfectants. Flow cytometric
analysis with Ricinus communis agglutinin I (RCAI) revealed an overall
greater number of Galbeta1,4GlcNAc structures in the fixed and
permeabilized SpcDNA3-Gal-T1 B cell transfectants compared with the
ASpcDNA3-Gal-T1 transfectants. Moreover, there was increased
galactosylation of IgG secreted from the SpcDNA3-Gal-T1 transfectants
relative to the ASpcDNA3-Gal-T1 B cell transfectants. Alteration of the
level of the "classical" beta4Gal-T (beta4Gal-T1) in B cells therefore
affects IgG glycosylation.
ORIGINAL ARTICLES
The effect on IgG glycosylation of altering beta1, 4- galactosyltransferase-1 activity in B cells
Department of Immunology, University College London, Windeyer Building, 46 Cleveland Street, London W1P 6DB, UK.
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