Membrane N-acetylglucosamine: expression by cells in rheumatoid synovial fluid, and by pre-cultured monocytes

After 21-48 h in culture, 2-8% of human peripheral blood monocytes strongly express terminal N-acetylglucosamine (GlcNAc) on their membranes. This can be detected with a monoclonal antibody selected for binding to asialo-agalacto-fetuin, and is eliminated by incubating the cells in pure N-acetylglucosaminidase. Expression of GlcNAc is transient, and can no longer be detected by day 4. These cells are a subset of macrophages since they are positive for non-specific esterase and stained by the monoclonal antibody EBM 11. GlcNAc-positive cells showing double staining with monoclonal antibodies UCHM1 and RFD7 were detected. Their numbers were not influenced by the addition of GM-CSF, IFN-gamma, 1,25-(OH)2 cholecalciferol or indomethacin. Macrophages which give membrane staining for terminal GlcNAc were also found in rheumatoid synovial fluid, and in synovial tissue, though in the peripheral blood their frequency was the same in samples from normal donors and from patients with rheumatoid arthritis. Immunoblots of 24-48-h monocyte cultures or of fresh synovial fluid cells using the anti-GlcNAc monoclonal, show the anticipated agalactosyl IgG heavy chains, and an additional band of 70-80kDa.