The effect of conditioned medium on the biosynthesis and glycosylation profile of acute phase proteins secreted by the human hepatoma cell line Hep G2 was studied. Conditioned medium was prepared from nonactivated [CM-LPS(-)] and ex vivo lipopolysaccharide activated [CM-LPS(+)] monocytes from eight patients with active rheumatoid arthritis (RA), five patients with active systemic lupus erythematosus (SLE), and seven healthy subjects. The biosynthesis of albumin, alpha 1-antichymotrypsin and alpha 1-proteinase inhibitor and the profile of glycosylation of proteinase inhibitor were analysed. CM-LPS(-) from patients with SLE had a similar effect to CM-LPS(-) from healthy subjects. In contrast, CM-LPS(-) from patients with RA had the same effect as CM-LPS(+) from healthy donors. A similar effect to that of CM-LPS(+) of healthy subjects was seen with CM-LPS(+) from patients with SLE and with CM-LPS(+) from patients with RA. The treatment of CM-LPS(+) with antibodies against interleukin 6 neutralised most of its ability to induce changes in the biosynthesis and glycosylation of acute phase proteins. Antibodies to interleukin 1 and tumour necrosis factor alpha had only a limited effect on the ability of CM-LPS(+) to induce changes of albumin and alpha 1-antichymotrypsin syntheses, whereas they had no effect on the biosynthesis and glycosylation of proteinase inhibitor. These results indicate that: (a) monocytes isolated from patients with active SLE and active RA have different capabilities of inducing alterations of acute phase proteins in vitro; (b) ex vivo activation of monocytes from patients with SLE leads to the full induction of its capabilities to change acute phase proteins, whereas the activation of monocytes from patients with RA has no additive effects; and (c) interleukin 6 seems to be a major cytokine involved in the regulation of the glycosylation pattern of acute phase proteins.
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