bDepamnent of P h a m l o J y cDepartment of C a n w Immunology dDepamnent oj'Rheumatology and ImmunologyUnivmity School @Medicine Panan, Poland 61 -701

We explored the possible role of transforming growth factor .I1 (TGF-fi), a cytokine that appears to be an TGF-,8 had no effect on haptoglobin or a,-acid glycoprotein secretion, either directly or in the presence of interleukin 6, which is capable of inducing these proteins. These studies demonstrate that TGF-fi can affect hepatic synthesis and secretion of a subset of acute-phase proteins, both directly and by modulating the effect of interleukin 6. The affected group of plasma proteins is distinct from those affected by other recognized acute-phase protein-inducing cytokines. These findings support the view that combinations of cytokines mediate the response of the hepatocyte to inflammatory stimuli.Tissue injury and infection lead to a broad array of systemic and metabolic alterations, collectively termed the acutephase response (1, 2). Among these alterations are changes in hepatic synthesis of a number of plasma proteins, referred to as acute-phase proteins; synthesis of some proteins, the positive acute-phase proteins, increases, while synthesis of others, the negative acute-phase proteins, decreases. Studies in primary hepatocyte cultures and hepatoma cell lines have shown that hepatic synthesis of human acute-phase proteins can be influenced by several cytokines including interleukin 6 (IL-6), a major inducer ofacute-phase changes, interleukins la and -p8 (IL-1), cachectin/tumor necrosis factor a (TNF), interferon y, and leukemia inhibitory factor (3-18). One cytokine can modulate the effect of other cytokines in human model systems-e.g., IL-1 diminishes the inducing effect of IL-6 on fibrinogen synthesis (7,12,18) and interferon yThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement"in accordance with 18 U.S.C. §1734 solely to indicate this fact.

We defined the acute phase behaviour of a number of rabbit plasma proteins in studies (in vivo) and studied the effects of monokine preparations on their synthesis by rabbit primary hepatocyte cultures. Following turpentine injection, increased serum levels of C-reactive protein, serum amyloid A protein, haptoglobin, ceruloplasmin, and decreased concentrations of albumin were observed. In contrast to what is observed in man, concentrations of alpha 2-macroglobulin and transferrin were increased. Co-culture of primary hepatocyte cultures with lipopolysaccharide-activated human peripheral blood monocytes or incubation with conditioned medium prepared from lipopolysaccharide-activated human or rabbit monocytes resulted in dose-dependent induction of serum amyloid A, haptoglobin, ceruloplasmin and transferrin and depression of albumin synthesis, while C-reactive protein synthesis and mRNA levels remained unchanged. A variety of interleukin-1 preparations induced dose-dependent increases in the synthesis and secretion of serum amyloid A, haptoglobin, ceruloplasmin and transferrin and decreased albumin synthesis. Human recombinant tumour necrosis factor (cachectin) induced a dose-dependent increase in synthesis of haptoglobin and ceruloplasmin. In general, human interleukin-1 was more potent than mouse interleukin-1 and tumour necrosis factor. None of the monokines we studied had an effect on C-reactive protein synthesis or mRNA levels. These data confirm that C-reactive protein, serum amyloid A, haptoglobin and ceruloplasmin display acute phase behaviour in the rabbit, and demonstrate that, in contrast to their behaviour in man, alpha 2M and transferrin are positive acute phase proteins in this species. While both interleukin-1 and tumour necrosis factor regulate biosynthesis of a number of these acute phase proteins in rabbit primary hepatocyte cultures, neither of these monokines induced C-reactive protein synthesis. Comparison of these findings with those in human hepatoma cell lines, in which interleukin-1 does not induce serum amyloid A synthesis, suggests that the effect of interleukin-1 on serum amyloid A synthesis may be indirect.

Undefined monocyte-derived cytokines have previously been shown to affect glycan processing in glycoproteins secreted by human hepatoma cell lines. Hep 3B cells, when incubated with the cytokine interferon beta 2/B-cell stimulating factor 2/interleukin 6, secreted forms of alpha 1-protease inhibitor, ceruloplasmin, and alpha-fetoprotein with increased reactivity with concanavalin A (Con A) while incubation of Hep G2 cells with this cytokine led to secretion of forms of these proteins with decreased reactivity with Con A, reflecting changes in their oligosaccharide chains. The difference in response of these two transformed cell lines to this cytokine undoubtedly reflects differences in their intracellular glycan processing mechanisms. Changes in glycosylation patterns were dissociated from changes in rate of synthesis: this cytokine caused increased synthesis of alpha 1-protease inhibitor and ceruloplasmin, and decreased synthesis of alpha-fetoprotein in both cell lines.