Aberrant control of galactosyltransferase in peripheral B lymphocytes and Epstein-Barr virus transformed B lymphoblasts from patients with rheumatoid arthritis.
It is now well established that hypogalactosylation of IgG is a molecular marker for rheumatoid arthritis (RA). However, the mechanism for the alteration of the galactosylation status has not been resolved. We compared the galactosyltransferase activities of anti-CD19 selected peripheral B lymphocytes of healthy subjects and patients with RA using ovalbumin as the acceptor substrate. In addition, certain samples of lymphocytes were assayed after Epstein-Barr virus (EBV) transformation and, also, the ability of bovine milk galactosyltransferase to galactosylate IgG in vitro was examined. Our results indicate that there is a significant difference between the galactosyltransferase activities of rheumatoid and control peripheral B lymphocytes and that EBV transformation causes a variable increase (15-1225%) in galactosyltransferase activity, over that present in the peripheral B lymphocytes from which the transformed cells were derived. Also the ubiquitous "lactose synthetase" type galactosyltransferase (EC 2.4.1.38) will galactosylate normal native IgG at concentrations of 500 mU/ml in vitro. We conclude that there is no evidence from our study for an IgG specific galactosyltransferase and that galactosyltransferase is an enzyme that is aberrantly modulated in peripheral B lymphocytes and EBV transformed B lymphoblasts derived from patients with RA.
Wilson
I B
IB
Glycobiology Institute, Department of Biochemistry, Oxford.
Platt
F M
FM
Isenberg
D A
DA
Rademacher
T W
TW
D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000201:enzymology* / Q000473:pathology; D001402:B-Lymphocytes / Q000201:enzymology*; D002472:Cell Transformation, Viral; D005260:Female; D005690:Galactose / Q000378:metabolism; D005700:Galactosyltransferases / Q000378:metabolism*; D004854:Herpesvirus 4, Human / Q000502:physiology*; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D013234:Stem Cells / Q000201:enzymology*
D007074:Immunoglobulin G; D005700:Galactosyltransferases; D005690:Galactose