Isolation and characterization of a novel liver-derived immunoinhibitory factor.

Cytosolic extracts prepared from perfused whole liver or purified hepatocytes of C57BL/6 mice inhibited interleukin-2--and concanavalin A--induced spleen cell proliferation in vitro. In contrast, cytosolic extracts from purified nonparenchymal liver cells had no effect. Arginase and very-low-density lipoprotein were previously identified as two immuninhibitory substances present in liver cytosolic extracts. We demonstrated, however, that inhibitory activity remained after removal of very-low-density lipoprotein and arginase from liver cytosolic extract by repeated ultracentrifugation and gel filtration chromatography, respectively, suggesting the presence of another inhibitor. Further purification by anion-exchange chromatography and chromatofocusing led to the isolation of a novel liver-derived immunohibitory factor. This liver-derived immunoinhibitory factor is sensitive to pronase digestion and heat and acid treatment; it has an estimated isoelectric point of 8.25. The Mr of liver-derived immunoinhibitory factor is 28 kD as estimated from its migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which is identical under both reducing and nonreducing conditions, indicating a monomeric nature of this protein. Amino acid composition analysis discloses that liver-derived immunoinhibitory factor is relatively rich in glycine and proline residues. Interleukin-2--induced spleen cell proliferation in vitro is inhibited by ths liver-derived immunoinhibitory factor, with a 50% inhibitory dose of 1.4 nmol/L. Furthermore, the biological activity of the liver-derived immunoinhibitory factor is not confined to mouse spleen cells, since the growth of B16 mouse melanoma and H35 rat hepatoma cells is also inhibited. A comparison with other liver-derived immunoinhibitors reported previously supports our claim that the liver-derived immunoinhibitory factor is a novel inhibitory protein.

Suppression of hepatic lymphokine-activated killer cell induction by murine Kupffer cells and hepatocytes.

Murine lymphokine-activated-killer cell activity was readily induced by culturing spleen cells with 10 U/ml of interleukin-2 for 4 days. In contrast, very little activity was generated under the same culture conditions when nonparenchymal liver cells were used as the responding cells. It was concluded that Kupffer cells produced prostaglandin and interferon alpha/beta, which suppressed lymphokine-activated-killer induction because (a) induction of lymphokine-activated-killer activity from nonparenchymal liver cells was observed in the presence of indomethacin and anti-interferon alpha/beta antibody; (b) when adherent nonparenchymal liver cells, primarily Kupffer cells, were removed, lymphokine-activated-killer activity could be obtained with interleukin-2 alone; (c) coculture of Kupffer cells with nonadherent nonparenchymal liver cells in a two-chambered system inhibited lymphokine-activated killer cell induction in a dose-dependent manner; (d) exogenous prostaglandin E2 and interferon alpha/beta added at the start of culture inhibited interleukin-2-induced cytotoxicity and proliferation, whereas the other major prostaglandin species in the liver, prostaglandin D2, had little effect. These findings are distinctive with Kupffer cells because splenic macrophages did not exert such inhibition in parallel experiments. Moreover, the supernatant collected from the 24-hr culture of nonparenchymal liver cells contained greater than 20-fold more prostaglandin E2 and interferon alpha/beta than that from culture of spleen cells. In subsequent in vivo experiments, when interleukin-2 was given intraperitoneally to mice, the combination of indomethacin and anti-interferon alpha/beta antibody significantly enhanced lymphokine-activated-killer activity recovered from the liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis and regulation of acute phase plasma proteins in primary cultures of mouse hepatocytes.

Adult mouse hepatocytes respond in vivo to experimentally induced acute inflammation by an increased synthesis and secretion of alpha 1-acid glycoprotein, haptoglobin, hemopexin, and serum amyloid A. Concurrently, the production of albumin and apolipoprotein A-1 is reduced. To define possible mediators of this response and to study their action in tissue culture, we established primary cultures of hepatocytes. Various hormones and factors that have been proposed to regulate the hepatic acute phase reaction were tested for their ability to modulate the expression of plasma proteins in these cells. Acute phase plasma and conditioned medium from activated monocytes influenced the production of most acute phase plasma proteins, and the regulation appears to occur at the level of functional mRNA. Purified hormones produced a significant anabolic response in only a few cases: dexamethasone was found to be effective in maintaining differentiated expression of the cells; and glucagon produced a specific inhibition of haptoglobin synthesis. When cells were treated with a combination of conditioned monocyte medium and dexamethasone, secretion of proteins was markedly reduced. The carbohydrate moieties of all plasma glycoproteins were incompletely modified, apparently as a result of decreased intracellular transport of newly synthesized plasma proteins. Although primary hepatocytes were not phenotypically stable in tissue culture, the cells nevertheless retained a broad response spectrum to exogenous signals. We propose this as a useful system to study the production of plasma proteins and thereby pinpoint the nature and activity of effectors mediating the hepatic acute phase reaction.

Host resistance in liver disease--its evaluation and therapeutic modification.

We have attempted to review some of the factors involved in host resistance and the variations in the individual responses to the infectious and noxious agents to which we are increasingly exposed. Few treatment modalities are available to favorably influence host resistance, but clearly, this approach to the treatment of liver disease represents an opportunity for the future.