Interferon beta 2/B-cell stimulatory factor type 2 shares identity with monocyte-derived hepatocyte-stimulating factor and regulates the major acute phase protein response in liver cells

B cell stimulating factor 2/interleukin 6 is a costimulant for human thymocytes and T lymphocytes

Growth and differentiation of thymocytes and mature T lymphocytes is regulated by cellular interactions that are in part mediated by soluble factors. We identify IL-6, formerly called B cell stimulating factor (BSF-2). IFN-beta 2, or hybridoma-plasmacytoma growth factor (HPGF) as a novel T cell costimulant rIL-6 induced a six-to seven-fold increase in proliferation of human thymocytes stimulated with suboptimal doses of PHA. A similar effect with added IL-6 could be observed using peripheral blood T lymphocytes, but only if the cultures were first rigorously depleted of monocytes that release high levels of IL-6. Analysis of the mechanism of the IL-6 effect on thymocytes and T lymphocytes showed that IL-6 did not lead to an increase in IL-2-R expression. Concentrations of antibody to IL-2-R inhibiting IL-2 effects did not block the IL-6-induced proliferation, indicating that the IL-6 effect was relatively IL-2 independent. These results identify IL-6 as a novel costimulant of human thymocytes and mature T lymphocytes, and suggest that IL-6 is also an important regulatory of cellular immunity.

Hepatocyte-stimulating factor, beta 2 interferon, and interleukin-1 enhance expression of the rat alpha 1-acid glycoprotein gene via a distal upstream regulatory region

The rat alpha 1-acid glycoprotein (AGP) gene is transcriptionally regulated by dexamethasone, interleukin 1 (IL-1), hepatocyte-stimulating factor, and beta 2 interferon. The steroid and peptide hormones stimulate expression of the AGP gene synergistically as well as independently. The regulatory sequence responsible for dexamethasone-stimulated expression has been localized previously to a region that is 120 to 64 base pairs (bp) upstream of the transcription start site (H. Baumann and L. E. Maquat, Mol. Cell. Biol. 6:2551-2561, 1986). To identify the regulatory sequence that is responsive to the peptide hormones, different lengths of the AGP gene 5'-flanking DNA were linked to the chloramphenicol acetyltransferase gene and then assayed for hormone-inducible chloramphenicol acetyltransferase gene expression in transiently transfected HepG2 cells. We demonstrate that an enhancer region that is responsive to IL-1, hepatocyte-stimulating factor, and beta 2 interferon lies within a 142-bp sequence located 5,300 to 5,150 bp upstream of the transcription start site. This distal regulatory region can confer hormone inducibility to a heterologous promoter; exert its affect in either orientation; and function, to a lesser degree, in nonhepatic but IL-1-responsive cells.

The essential role of B cell stimulatory factor 2 (BSF-2/IL-6) for the terminal differentiation of B cells

The role of recombinant B cell stimulatory factor 2 (BSF-2/IL-6) in the regulation of growth and differentiation of B cells was investigated. rBSF-2 at 200 pg/ml could induce 50% of the maximum Ig production in B lymphoblastoid cell lines, the specific activity being estimated as 5 X 10(6) U/mg. rBSF-2 augmented PWM-induced IgM, IgG, and IgA production in mononuclear cells (MNC); the effect was exerted by directly acting on PWM-induced B blast cells to induce Ig production. However, rBSF-2 did not induce any growth of activated B cells. In contrast, rBSF-2 showed a potent growth activity on a murine hybridoma clone, MH60.BSF2. The concentration required for half-maximal [3H]TdR uptake was approximately 5 pg/ml, which was 40 times less than that required for Ig induction in a B cell line. Anti-BSF-2 antibody inhibited PWM-induced Ig production in MNC, but not PWM-induced proliferation. The antibody was effective even when added on day 4 of an 8-d culture, indicating that BSF-2 is one of the essential late-acting factors in PWM-induced Ig production.

cDNA cloning of murine interleukin-HP1: homology with human interleukin 6

Interleukin-HP1 (HP1) is a murine T cell-derived lymphokine, originally described as a growth factor for B cell hybridomas and plasmacytomas, that was recently shown to stimulate growth and differentiation of normal B and T lymphocytes. Here, we describe a cDNA for HP1 that was isolated from a library prepared using mRNA of a murine helper T cell clone activated with a clonotypic antibody. The cDNA, which hybridizes with a mRNA of approximately 1300 bp, encodes a polypeptide consisting of 211 amino acids with a typical signal sequence of 24 residues followed by 187 amino acids, which form the mature protein (Mr = 21,710). No N-glycosylation site but several potential O-glycosylation sites were identified in the predicted sequence. Comparison of the cDNA sequence of HP1 with that of human interleukin 6 disclosed a homology of 65% at the DNA level and of 42% at the protein level with a maximum of 57% for the segment spanning residues 42-102 of mature HP1. Considering the functional homology that was previously established between these two proteins, we therefore propose that HP1 be renamed murine interleukin 6.

Monocyte-derived human B-cell growth factor identified as interferon-beta 2 (BSF-2, IL-6)

Soluble products of either Epstein-Barr virus (EBV)-infected B cells or activated monocytes promote the proliferation of EBV-infected B cells and permit their growth at low cell densities. This suggests that growth factors are important for B-cell immortalization by EBV. In this study, a monocyte-derived factor that promotes the growth of EBV-infected b cells was purified and identified as interferon-beta 2 (IFN-beta 2), which is also known as 26-kilodalton protein, B-cell differentiation factor (BSF-2), and interleukin-6 (IL-6). The purified protein has a specific activity of approximately 4 X 10(7) units per milligram of protein in assays of B-cell growth. Thus, IFN-beta 2/BSF-2 is a B-cell growth factor that promotes the proliferation of human B cells infected with EBV.

Interleukin-6 (IL-6) in synovial fluid and serum of patients with rheumatic diseases

Interleukin-6 (IL-6) is a monokine with a number of biological activities, which are intimately related to inflammatory responses. We have measured IL-6 levels in synovial fluid (SF) and serum (Se) of patients with rheumatic diseases. SF-IL-6 levels were a thousand-fold higher than corresponding Se levels and a positive correlation was found between SF and Se levels suggesting that Se-IL-6 is derived from IL-6 produced in the joint. Se levels of IL-6 were also positively correlated to C-reactive protein (CRP) levels, supporting the in vitro experiments showing that IL-6 stimulates hepatocytes to produce CRP. Finally we observed a positive correlation between SF-IL-6 levels and the local activity score.

Cytokines: molecular and biological characteristics

Cytokines are soluble molecules with many cells as the source of their origin and as targets for their actions. They are pleiotropic in their biological functions. Some cytokines are distinct with respect to their molecular structure yet they have overlapping biological properties (Interleukin 1 and tumor necrosis factors). Others are structurally distinct and often have contrasting biological activities (e.g. tumor necrosis factors and transforming growth factor-beta). In this article I have briefly reviewed the molecular and biological properties of four cytokines that appears to play an important role in the pathogenesis of certain immunoinflammatory disorders. It is also to be stressed that there are additional cytokines (e.g. granulocyte-monocyte colony stimulating factors, interleukin 2, interferons etc.) that could also play a role in the pathogenesis of immunoinflammatory disorders.

Hepatocyte-stimulating factor, beta 2 interferon, and interleukin-1 enhance expression of the rat alpha 1-acid glycoprotein gene via a distal upstream regulatory region

The rat alpha 1-acid glycoprotein (AGP) gene is transcriptionally regulated by dexamethasone, interleukin 1 (IL-1), hepatocyte-stimulating factor, and beta 2 interferon. The steroid and peptide hormones stimulate expression of the AGP gene synergistically as well as independently. The regulatory sequence responsible for dexamethasone-stimulated expression has been localized previously to a region that is 120 to 64 base pairs (bp) upstream of the transcription start site (H. Baumann and L. E. Maquat, Mol. Cell. Biol. 6:2551-2561, 1986). To identify the regulatory sequence that is responsive to the peptide hormones, different lengths of the AGP gene 5'-flanking DNA were linked to the chloramphenicol acetyltransferase gene and then assayed for hormone-inducible chloramphenicol acetyltransferase gene expression in transiently transfected HepG2 cells. We demonstrate that an enhancer region that is responsive to IL-1, hepatocyte-stimulating factor, and beta 2 interferon lies within a 142-bp sequence located 5,300 to 5,150 bp upstream of the transcription start site. This distal regulatory region can confer hormone inducibility to a heterologous promoter; exert its affect in either orientation; and function, to a lesser degree, in nonhepatic but IL-1-responsive cells.