Human macrophage-derived chemokine (MDC), a novel chemoattractant for monocytes, monocyte-derived dendritic cells, and natural killer cells.

A cDNA encoding a novel human chemokine was isolated by random sequencing of cDNA clones from human monocyte-derived macrophages. This protein has been termed macrophage-derived chemokine (MDC) because it appears to be synthesized specifically by cells of the macrophage lineage. MDC has the four-cysteine motif and other highly conserved residues characteristic of CC chemokines, but it shares <35% identity with any of the known chemokines. Recombinant MDC was expressed in Chinese hamster ovary cells and purified by heparin-Sepharose chromatography. NH2-terminal sequencing and mass spectrophotometry were used to verify the NH2 terminus and molecular mass of recombinant MDC (8,081 dalton). In microchamber migration assays, monocyte-derived dendritic cells and IL-2-activated natural killer cells migrated to MDC in a dose-dependent manner, with a maximal chemotactic response at 1 ng/ml. Freshly isolated monocytes also migrated toward MDC, but with a peak response at 100 ng/ml MDC. Northern analyses indicated MDC is highly expressed in macrophages and in monocyte-derived dendritic cells, but not in monocytes, natural killer cells, or several cell lines of epithelial, endothelial, or fibroblast origin. High expression was also detected in normal thymus and less expression in lung and spleen. Unlike most other CC chemokines, MDC is encoded on human chromosome 16. MDC is thus a unique member of the CC chemokine family that may play a fundamental role in the function of dendritic cells, natural killer cells, and monocytes.

A highly selective CC chemokine receptor (CCR)8 antagonist encoded by the poxvirus molluscum contagiosum.

The MC148 CC chemokine from the human poxvirus molluscum contagiosum (MCV) was probed in parallel with viral macrophage inflammatory protein (vMIP)-II encoded by human herpesvirus 8 (HHV8) in 16 classified human chemokine receptors. In competition binding using radiolabeled endogenous chemokines as well as radiolabeled MC148, MC148 bound with high affinity only to CCR8. In calcium mobilization assays, MC148 had no effect on its own on any of the chemokine receptors, but in a dose-dependent manner blocked the stimulatory effect of the endogenous I-309 chemokine on CCR8 without affecting chemokine-induced signaling of any other receptor. In contrast, vMIP-II acted as an antagonist on 10 of the 16 chemokine receptors, covering all four classes: XCR, CCR, CXCR, and CX(3)CR. In chemotaxis assays, MC148 specifically blocked the I-309-induced response but, for example, not stromal cell-derived factor 1alpha, monocyte chemoattractant protein 1, or interleukin 8-induced chemotaxis. We thus concluded that the two viruses choose two different ways to block the chemokine system: HHV8 encodes the broad-spectrum chemokine antagonist vMIP-II, whereas MCV encodes a highly selective CCR8 antagonist, MC148, conceivably to interfere with monocyte invasion and dendritic cell function. Because of its pharmacological selectivity, the MC148 protein could be a useful tool in the delineation of the role played by CCR8 and its endogenous ligand, I-309.

Cytokine production by cholesterol-loaded human peripheral monocyte-macrophages: the effect on fibrinogen mRNA levels in a hepatoma cell-line (HepG2).

Conditioned medium from human monocyte-macrophages incubated under various conditions was tested for its ability to stimulate fibrinogen mRNA levels in the hepatoma cell line HepG2. Recombinant human interleukin-6 (IL-6) stimulated fibrinogen mRNA levels 4.4-fold over control levels; this response was blocked by an anti-IL-6 antibody. Conditioned medium from 3-day-cultured monocyte-macrophages produced a slight stimulation of fibrinogen synthesis in HepG2 cells which was enhanced when the monocyte-macrophages had been treated with lipopolysaccharide (LPS). This stimulation was blocked by the anti IL-6 antibody. The cytokines, interleukin-1 (IL-1) and tumour necrosis factor (TNF) were also detected in the conditioned medium from the 3-day-cultured monocyte-macrophages. Monocyte-macrophages were cultured for 17 days and then incubated with acetylated low density lipoprotein (AcLDL) for 48 h. Such cells were 'foamy' in appearance and showed a 4-fold increase in apoE mRNA and a 10 to 50-fold increase in apoE secretion. This increase in apoE production was suppressed by almost a third when cells were coincubated with AcLDL and LPS. Conditioned medium from these 17-day-cultured AcLDL-treated human monocyte-macrophages did not stimulate fibrinogen mRNA synthesis in HepG2 cells, nor did the conditioned medium contain detectable levels of cytokines. These results suggest that cytokine production from foam cells in the atherosclerotic lesion is unlikely to be a major contributing factor in determining the elevated fibrinogen levels seen in the plasma of patients with IHD.

Monocyte chemotactic protein-4: tissue-specific expression and signaling through CC chemokine receptor-2.

Chemokines constitute a family of low-molecular-weight proteins that attract or activate a variety of cell types, including leukocytes, endothelial cells, and fibroblasts. An electronic search of the GenBank Expressed Sequence Tags database uncovered a partial cDNA sequence with homology to the chemokine monocyte chemotactic protein-1 (MCP-1). Isolation of the full-length clone revealed that it encodes the chemokine MCP-4, an eosinophil chemoattractant recently described by Uguccioni et al. [J. Exp. Med. 183, 2379-2384]. Recombinant MCP-4 was expressed in mammalian cells and purified by heparin-Sepharose chromatography. Sequencing the amino terminus of this protein corroborated the reported sequence of recombinant MCP-4 produced in insect cells. As shown by calcium flux assays, MCP-4 activated the cloned G protein-coupled receptor CCR-2, which also recognizes MCP-1 and MCP-3. Northern hybridization indicated that MCP-4 is constitutively expressed at high levels in the small intestine, colon, and lung. This expression profile is consistent with its role as a chemoattractant for eosinophils, which can be rapidly mobilized to the lung or intestine in response to invading pathogens. In marked contrast to MCP-1, MCP-4 was not induced in cell lines treated with pro-inflammatory stimuli such as lipopolysaccharide or tumor necrosis factor alpha.

New members of the chemokine receptor gene family.

Chemokines are relatively small peptides with potent chemoattractant and activation activities for leukocytes. Several chemokine receptors have been cloned and characterized and all are members of the G protein-coupled receptor superfamily. Using degenerate oligonucleotides and polymerase chain reaction, we have identified seven novel receptors. Two of these sequences are presented here for the first time. We have shown, with gene mapping studies, that receptors with the highest sequence similarity are closely linked on human chromosomes. This close genetic association suggests a functional relationship as well.

Profile of human macrophage transcripts: insights into macrophage biology and identification of novel chemokines.

High throughput partial sequencing of randomly selected cDNA clones has proven to be a powerful tool for examining the relative abundance of mRNAs and for the identification of novel gene products. Because of the important role played by macrophages in immune and inflammatory responses, we sequenced over 3000 randomly selected cDNA clones from a human macrophage library. These sequences represent a molecular inventory of mRNAs from macrophages and provide a catalog of highly expressed transcripts. Two of the most abundant clones encode recently identified CC chemokines. Macrophage-derived chemokine (MDC) plays a complex role in immunoregulation and is a potent chemoattractant for dendritic cells, T cells, and natural killer cells. The chemokine receptor CCR4 binds MDC with high affinity and also responds by calcium flux and chemotaxis. CCR4 has been shown to be expressed by Th2 type T cells. Recent studies also implicate MDC as a major component of the host defense against human immunodeficiency virus.

Production of interleukin-1 and interleukin-6 by human keratinocytes and squamous cell carcinoma cell lines.

Cultured human keratinocytes and squamous cell carcinoma (SCC) cell lines were analyzed for the presence of ribonucleic acid (RNA) transcripts for the cytokines interleukin-1 and interleukin-6 and for these proteins. This study demonstrates that both cytokines are synthesized and secreted by both normal keratinocytes and SCC lines. The rate of secretion of these cytokines can be augmented in response to a variety of stimuli including tumor necrosis factor-alpha, granulocyte-macrophage colony stimulating factor, transforming growth factor-beta and the combination of lipopolysaccharide and phorbol myristate acetate. Interleukin-1 and interleukin-6 have been reported to influence the proliferation of cultured human fibroblasts. However, these cytokines had no significant effect on the proliferation of human keratinocytes or the SCC lines tested. Although it seems unlikely that interleukin-1 or interleukin-6 could directly influence keratinocyte proliferation in vivo, the capacity of these cells to synthesize and release these cytokines supports earlier observations that keratinocytes may play an important role in augmenting an immune or inflammatory response.

Chemokine expression in murine experimental allergic encephalomyelitis.

Chemokines are a family of low molecular mass proteins with chemotactic and cell activating activities. Reverse transcription-polymerase chain reaction and Northern hybridization were used to examine their expression during murine experimental allergic encephalomyelitis (EAE), an autoimmune disease used as a model of multiple sclerosis. The mRNAs encoding RANTES, MIP-1 alpha, MIP-1 beta, TCA3 (I-309), IP-10, JE (MCP-1), KC (MGSA/gro), and MARC (MCP-3) were induced in the spinal cord 1-2 days before clinical signs were apparent. SDF, a cDNA predicted to encode a chemokine-like product, was expressed in normal as well as diseased spinal cords. No expression of C10 or MIP-2 was detected. Activated encephalitogenic T cells expressed message for RANTES, MIP-1 alpha, MIP-1 beta, and TCA3. These results define a subset of chemokines that may play an important role in the inflammatory process during murine EAE.

Interleukin 1 (IL-1) and tumour necrosis factor synergise in the induction of IL-1 synthesis by human vascular endothelial cells.

We have demonstrated that recombinant interleukin 1 (IL-1) induces IL-1 alpha and IL-1 beta production by human vascular endothelial cells (EC) in vitro. The effect of IL-1 on EC was dose-dependent and not due to contamination by endotoxin or secondary to the production of tumour necrosis factor (TNF). Thymocyte co-mitogenesis was shown to be due to IL-1 by treating EC supernatants with neutralising antibodies specific for IL-1 alpha and IL-1 beta. Recombinant TNF alpha synergised with IL-1 in the induction of IL-1 secretion by EC. Synergy was particularly striking at concentrations of IL-1 and TNF which, when used alone, had no effect - 2 U/ml IL-1 with 10 U/ml TNF. Thus we provide more evidence that EC play an important role in the perpetuation or possibly even initiation of chronic inflammation by amplifying cytokine production initiated by small numbers of infiltrating leucocytes.

Murine pregnancy-associated modulations in lymphocyte reactivity to mitogens: identification of the cell populations affected.

Lymphocytes from the thymus, spleen and inguinal lymph nodes of syngeneically pregnant and non-pregnant mice were compared in their responsiveness to polyclonal stimulation by mitogen. Pregnancy-associated changes in mitogen reactivity were detected, on a cell-per-cell basis, in thymocytes (increased) and spleen cells (decreased) but not in lymph node cells. The hyperreactivity of thymocytes during pregnancy correlated with physiological involution of the thymus occurring through the selective loss of relatively immature, non-mitogen-reactive, Lyt 1+2+ cells. The remaining cells were found largely to be mature Lyt 1+2- T cells with the capacity to respond to mitogenic stimulation. It is most likely the relative increase in the proportion of these Lyt 1+2- cells that causes the hyper-responsiveness of thymocytes to mitogens observed during pregnancy. On the other hand, while spleen cells from pregnant animals gave lower responses to mitogens than those from control virgin females, isolated splenic T cells from the two groups proved equally reactive to T cell mitogens. This supports the contention that at least some aspects of immunity during pregnancy are down-regulated by inhibitory cells within the non-T cell compartment. The results demonstrate the importance of identifying the reactive cell population in studies on changes in lymphocyte responsiveness in pregnancy.

Quantitation of chemokines (MDC, TARC) expression in mucosa from Crohn's disease and ulcerative colitis.

Chemokines and their receptors are involved in the migration of different mononuclear cells. Among them macrophages-derived chemokines (MDC) and thymus-and activation regulated chemokine (TARC) belong to a new cluster of genes involve in Th2 lymphocytes homing. Cytokines appear to play a significant role in pathogenesis of inflammatory bowel diseases with an excessive Th1 response in chronic lesions of Crohn's disease (CD) and a Th2 pattern in both earlier mucosal CD lesions and in mucosa of ulcerative colitis (UC). Here we demonstrate that RNAm coding for MDC and TARC are expressed in mucosa from CD and UC patients. Using real-time fluorescent RT-PCR, MDC and TARC mRNA were increased in CD inflamed mucosa. Moreover MDC and TARC transcripts were increased in inflamed CD specimen compared to non-involved CD mucosa. These differences both discriminate CD from UC patients. Additionally, MDC protein was produced in isolated mononuclear cells from peripheral blood (PBMC) or mucosa (LPMC) from UC and CD patients: spontaneously, MDC production from PBMC was increased in CD compared to UC patients. MDC production from CD PBMC was also higher than that found in healthy controls. Together, these data indicate that MDC should be involved in the lymphocytes homing in mucosa from CD patients.

Metaphor: exploring its origins and therapeutic use in death, dying and bereavement.

Metaphor is a commonly used and powerful language device for expressing complex thoughts or feelings. This exploratory qualitative study examined the sources and function of metaphor in relation to death, dying and bereavement. The study involved focus group discussions and follow-up questionnaires with professionals from three different contexts (nursing, hospice and bereavement counselling), and gave rise to a number of interesting observations. The results have implications for professional carers, particularly those working in dying and bereavement contexts, in relation to facilitating the use of metaphor to enhance the quality of communication. Suggestions are made for further research.

Post-transcriptional control of IL-1 gene expression in the acute monocytic leukemia line THP-1.

The acute monocytic leukemia cell line THP-1 secretes predominantly IL-1 beta after treatment with bacterial lipopolysaccharide and tumour promoting phorbol ester (PMA). IL-1 alpha is also secreted, but represents less than 10% of the total IL-1 activity. This differential is reflected at the level of mRNA as IL-1 beta mRNA is more abundant than IL-1 alpha mRNA. Studies of transcription in isolated nuclei however indicate that each gene is transcribed at a similar rate, suggesting that post-transcriptional mechanisms regulate the relative abundance of IL-1 alpha and IL-1 beta mRNA. Measurement of RNA half life after addition of alpha-amanitin (an inhibitor of RNA polymerase II) indicate that IL-1 alpha mRNA is not as stable as IL-1 beta mRNA suggesting one mechanism for the different relative levels of RNA.

Transforming growth factor beta induces the production of interleukin 6 by human peripheral blood mononuclear cells.

Previous studies have indicated that the cytokine transforming growth factor beta 1 (TGF beta 1) has immunosuppressive properties and can inhibit the production of tumor necrosis factor (TNF) and Interleukin 1 (IL 1) by human peripheral blood mononuclear cells. In this study, we have examined the effects of TGF beta 1 on the production of Interleukin 6 (IL 6) by human peripheral blood mononuclear cells. Treatment with only TGF beta 1 leads to the induction of IL 6, and this was both dose- and time-dependent. The effect of TGF beta 1 was evident at the level of IL 6 mRNA, suggesting TGF beta 1-induced de novo synthesis of IL 6. Induction of IL 6 by TGF beta 1 was specific, as other cytokines made by mononuclear cells (TNF and IL 1) were not induced by TGF beta 1. Furthermore, when a panel of stimuli were compared for their ability to induce IL 1, TNF and IL 6 in the presence or absence of TGF beta 1, IL 6 levels were augmented in the presence of TGF beta 1, while the induction of IL 1 and TNF was inhibited significantly. These results indicate that TGF beta 1 has complex effects on the production of cytokines by peripheral blood mononuclear cells and that TGF beta 1 is not inhibitory for all cytokine production. The ability of TGF beta 1 to induce IL 6 suggests that IL 6 may mediate some of the effects of TGF beta 1.

Interleukin 7 (murine pre-B cell growth factor/lymphopoietin 1) stimulates thymocyte growth: regulation by transforming growth factor beta.

The effects of interleukin 7 (IL7) previously known as murine pre-B cell growth factor/lymphopoietin 1 on the growth of murine thymocytes was investigated. In the presence of a suboptimal dose of phytohemagglutinin, IL7 induced a dose-dependent increase in thymocyte proliferation which was comparable to that induced by IL1. Additionally IL7 was shown to synergize with a suboptimal dose of IL1 to enhance thymocyte proliferation. Thymocyte proliferation induced by IL7, like that induced by IL1, was inhibited when either recombinant transforming growth factor (TGF) beta 1 or beta 2 were added at the initiation of culture. Interestingly, IL7-driven thymocyte proliferation was considerably less susceptible to inhibition by TGF-beta 1 or TGF-beta 2 than that induced by IL1. Taken together these results suggest IL7 may activate distinct populations of thymocytes and/or act through a pathway distinct from that utilized by IL1.

Effect of cytokines on HLA-DR and IL-1 production by a monocytic tumour, THP-1.

The monocytic tumour, THP-1, expresses many of the properties of monocytes, both by cell surface staining and its capacity to produce monokines. It was used as a source of homogenous monocytic cells as a model to determine whether a variety of highly purified or recombinant cytokines could induce HLA-DR expression and the production of interleukin-1 (IL-1). Interferon-gamma (IFN-gamma) alone induced HLA-DR. Tumour necrosis factor (TNF), lymphotoxin (LT) and granulocyte-macrophage colony-stimulating factor (GM-CSF) alone were able to induce IL-1 but not HLA-DR. When IFN-gamma was combined with TNF, induction of HLA-DR and IL-1 was enhanced in a synergistic manner. These effects were detectable at a pretranslational level as synergistic effects were observed on DR alpha mRNA and IL-1 beta mRNA levels. The results demonstrate the specificity of IFN-gamma as the inductive stimulus for HLA-DR expression by THP-1 cells. As IFN-gamma and TNF are products of activated T cells, the synergistic role for these molecules in macrophage activation is discussed.

Modulation of cytokine production by transforming growth factor-beta.

Transforming growth factor-beta 1 (TGF-beta 1) is one of a family of polypeptides involved in the regulation of cell growth and differentiation. The effects of human rTGF-beta 1 on the production of IL-1 and TNF by activated PBMC were studied. The addition of TGF-beta 1 alone caused an increase in the levels of mRNA for IL-1 alpha, IL-1 beta, and TGF-alpha. This was due to increased transcription rather than enhanced mRNA stability. The induced mRNA were of the appropriate size as assessed by Northern blotting. However, the mRNA did not appear to be translated into protein, inasmuch as the translation products of IL-1 beta and TNF-alpha were not detected by RIA or ELISA. Furthermore, in experiments utilizing a neutralizing antibody to TGF-beta 1, we were unable to unmask IL-1 biologic activities and unable to detect TNF biologic activity in the WEHI 164 cytotoxicity assay. TGF-beta inhibited in a dose-dependent manner the induction of IL-1 beta by LPS or TNF but not by PHA and PMA. Similarly, LPS induction of TNF-alpha was blocked by TGF-beta, whereas induction of PMA and PHA was completely resistant. TGF-beta 1 did not increase PGE2 secretion or cause elevated intracellular cAMP; thus, the inhibitory effects of TGF-beta 1 seem not to be mediated by PGE2 or cAMP, which have both been implicated in post-transcriptional control of cytokine gene expression. These findings suggest a dual role for TGF-beta 1 in the regulation of cytokine production at both transcriptional and translational levels.

Detection of transforming growth factor-beta in rheumatoid arthritis synovial tissue: lack of effect on spontaneous cytokine production in joint cell cultures.

The presence of transforming growth factor-beta (TGF-beta) in inflammatory joint disease was investigated. Synovial fluid from patients with rheumatoid arthritis (RA) and patients with other non-autoimmune inflammatory joint diseases contained high levels of both active and latent TGF-beta. Levels of active TGF-beta did not correlate with drug regimen in either patient group or with the recovery period in the individuals with non-RA joint disease. Freshly isolated synovial cells from individuals with RA were shown by Northern blotting to express the mRNA for TGF-beta 1 and to secrete latent TGF-beta protein which could be neutralized by antibodies to TGF-beta 1 and TGF-beta 2. Lipopolysaccharide-stimulated peripheral blood mononuclear cells from normal donors produced interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF-alpha) which was inhibited by pretreatment of these cells with recombinant TGF-beta. Cytokine production was not inhibited if the addition of TGF-beta was used after the inducing stimulus, suggesting that in activated cells cytokine production cannot be inhibited. This was confirmed by the observation that neither TGF-beta 1 or TGF-beta 2 inhibited spontaneous IL-1 or TNF-alpha production by rheumatoid synovial mononuclear cells in culture. These findings show that despite the presence of active TGF-beta in RA synovial joints and the spontaneous production of latent (potentially active) TGF-beta by RA cells in culture, additional TGF-beta did not inhibit ongoing cytokine synthesis in vitro. This suggests that TGF-beta may not inhibit cytokine production in the rheumatoid joint although it cannot be ruled out that in vivo TGF-beta already has an immunosuppressive effect which cannot be further increased in vitro by exogenous protein.

Cloning of human tumor necrosis factor (TNF) receptor cDNA and expression of recombinant soluble TNF-binding protein.

The cDNA for one of the receptors for human tumor necrosis factor (TNF) has been isolated. This cDNA encodes a protein of 455 amino acids that is divided into an extracellular domain of 171 residues and a cytoplasmic domain of 221 residues. The extracellular domain has been engineered for expression in mammalian cells, and this recombinant derivative binds TNF alpha with high affinity and inhibits its cytotoxic activity in vitro. The TNF receptor exhibits similarity with a family of cell surface proteins that includes the nerve growth factor receptor, the human B-cell surface antigen CD40, and the rat T-cell surface antigen OX40. The TNF receptor contains four cysteine-rich subdomains in the extracellular portion. Mammalian cells transfected with the entire TNF receptor cDNA bind radiolabeled TNF alpha with an affinity of 2.5 x 10(-9) M. This binding can be competitively inhibited with unlabeled TNF alpha or lymphotoxin (TNF beta).

Granulocyte-macrophage colony stimulating factor induces both HLA-DR expression and cytokine production by human monocytes.

The effect of recombinant human granulocyte-macrophage colony stimulating factor (GM-CSF) on the expression of HLA-DR, and the production of the cytokines interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) by human peripheral blood monocyte-enriched populations was investigated. GM-CSF was shown to induce both the expression of HLA-DR and the cytokines IL-1 and TNF alpha in a dose-dependent manner. In contrast, interferon-gamma (IFN-gamma), which induced major histocompatibility complex (MHC) class II expression, did not induce IL-1 or TNF alpha production. However, IFN-gamma enhanced the cell surface expression of HLA-DR and the production of IL-1 and TNF alpha on monocyte-enriched cells stimulated by GM-CSF. By itself, GM-CSF did not induce surface class II expression on the human monocytic tumour cell line THP-1, whereas it synergized with IFN-gamma to induce surface expression. These cells responded to GM-CSF by producing IL-1 and TNF alpha; Northern blotting showed that mRNA levels of IL-1 and TNF alpha were transiently induced, similar to other cytokines. Our results indicate that GM-CSF is a major macrophage activating factor that is capable of inducing both the expression of HLA-DR and the cytokines involved in T-cell activation by macrophages; therefore, GM-CSF may be of importance in potentiating antigen presenting function.