Related Experiment Video
Updated: Aug 8, 2026
Isolation of CD133+ Liver Stem Cells for Clonal Expansion
Published on: October 10, 2011
Isolation and characterization of a novel liver-derived immunoinhibitory factor
S P Tzung1, K C Gaines, M Henderson
1Department of Medicine, Veterans Administration Medical Center Sciences, Buffalo, NY 14215.
Insights
Researchers discovered a novel liver-derived inhibitory protein that suppresses immune cell proliferation and tumor cell growth. This protein, distinct from previously known inhibitors, offers new insights into liver-based immunomodulation and potential therapeutic targets.
Area of Science:
- Immunology
- Hepatology
- Biochemistry
Background:
- Liver cytosolic extracts from C57BL/6 mice inhibit T-cell proliferation.
- Previously identified inhibitors (arginase, VLDL) do not account for all inhibitory activity.
Purpose of the Study:
- To isolate and characterize a novel immunoinhibitory factor from liver cytosolic extracts.
- To determine the properties and biological activity of this newly identified factor.
Main Methods:
- Cytosolic extracts from mouse liver and hepatocytes were used.
- Purification involved ultracentrifugation, gel filtration, anion-exchange chromatography, and chromatofocusing.
- Characterization included sensitivity to proteases/heat/acid, isoelectric focusing, SDS-PAGE, and amino acid analysis.
Main Results:
- A novel liver-derived immunoinhibitory factor (28 kD, pI 8.25) was isolated.
- This factor is a monomeric protein, rich in glycine and proline.
- It potently inhibits interleukin-2-induced spleen cell proliferation (IC50 = 1.4 nmol/L) and tumor cell growth (B16 melanoma, H35 hepatoma).
Conclusions:
- A novel, potent immunoinhibitory protein exists in liver cytosol, distinct from known inhibitors.
- This protein exhibits broad inhibitory activity against immune and tumor cells.
- It represents a significant new finding in liver-derived immunomodulatory factors.
Abstract:
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.
