Human recombinant interferon-inducible protein-10: intact disulfide bridges are not required for inhibition of hematopoietic progenitors and chemotaxis of T lymphocytes and monocytes

Human recombinant interferon-inducible protein-10 (rIP-10), a C-X-C chemokine, inhibits proliferation of human hematopoietic progenitors responsive to co-stimulation by recombinant steel factor (rSLF), is chemotactic for human monocytes and T-lymphocytes, and promotes T-lymphocyte adhesion to endothelial cells. Because chemokines have four conserved cysteines forming two intramolecular disulfide bridges, we decided to investigate their contribution in the biological activity of rIP-10. Since amino acid residues 22-98 of the sequence predicted by the cDNA constitute the naturally occurring IP-10, they were cloned after an initiating methionine into expression vector pET-3d. Subsequently rIP-10 was purified by enzymatic cell lysis, solubilization of refractile bodies with guanidine hydrochloride, renaturation by dialysis against dilute acetic acid, and sequential ion-exchange and reverse-phase high-performance liquid chromatography. Purified rIP-10 was reduced with 20 mM dithiothreitol, and chemically modified with 100 mM iodoacetamide (IAA), or S-methyl-methanethiosulfonate (MMTS), or N-methylmaleimide (NMM). Radiolabeling experiments demonstrated that 95% of the rIP-10 thiols were modified, and this was confirmed with SDS-PAGE. The biological activity of modified rIP-10 was determined in vitro by inhibition of rSLF-responsive human bone marrow hematopoietic progenitor proliferation and by chemotaxis assays using human T-lymphocytes and monocytes. In both assay systems, the biological activity was evident at rIP-10 concentrations of 20-100 ng/ml. The activity was preserved after modification of rIP-10 by IAA or MMTS, but was abolished after modification by NMM. We conclude that disulfide bridges are not essential for the biological activity of rIP-10.

RANTES potentiates antigen-specific mucosal immune responses

RANTES is produced by lymphoid and epithelial cells of the mucosa in response to various external stimuli and is chemotactic for lymphocytes. The role of RANTES in adaptive mucosal immunity has not been studied. To better elucidate the role of this chemokine, we have characterized the effects of RANTES on mucosal and systemic immune responses to nasally coadministered OVA. RANTES enhanced Ag-specific serum Ab responses, inducing predominately anti-OVA IgG2a and IgG3 followed by IgG1 and IgG2b subclass Ab responses. RANTES also increased Ag-specific Ab titers in mucosal secretions and these Ab responses were associated with increased numbers of Ab-forming cells, derived from mucosal and systemic compartments. Splenic and mucosally derived CD4(+) T cells of RANTES-treated mice displayed higher Ag-specific proliferative responses and IFN-gamma, IL-2, IL-5, and IL-6 production than control groups receiving OVA alone. In vitro, RANTES up-regulated the expression of CD28, CD40 ligand, and IL-12R by Ag-activated primary T cells from DO11.10 (OVA-specific TCR-transgenic) mice and by resting T cells in a dose-dependent fashion. These studies suggest that RANTES can enhance mucosal and systemic humoral Ab responses through help provided by Th1- and select Th2-type cytokines as well as through the induction of costimulatory molecule and cytokine receptor expression on T lymphocytes. These effects could serve as a link between the initial innate signals of the host and the adaptive immune system.

Role for CD40-CD40 ligand interactions in the immune response to solid tumours

CD40-mediated interactions play an important role in the response to infections, transplantation, and cancer by affecting the development, activation, proliferation and differentiation of a variety of immune cells. In the current study we examined the role of CD40-mediated interactions in immune responses to bladder, pancreatic and breast carcinomas as well as melanoma cell lines using soluble human CD40L (rhCD40L) or anti-CD40 mAb in vitro. CD40 expression was readily detected in a large proportion of the cell lines and was augmented but not induced de novo by treatment with IFNgamma. Treatment of CD40-positive cell lines with rhCD40L or anti-CD40mAb enhanced cell surface expression of ICAM-1 and FAS and stimulated the production of IL-6, IL-8, GROalpha, GM-CSF and TNFalpha but not IL-4, IL-10, TGFbeta, MCP-1, RANTES, MIP-1beta, or IP-10. In addition, incubation of CD40+ tumour cell lines with immobilised rhCD40L or anti-CD40 mAb in vitro resulted in significant inhibition of proliferation and a corresponding decrease in viability. This CD40-mediated inhibition of cell growth was due, at least in part, to alterations in cell cycle and the induction of apoptosis. Transfection of CD40-negative tumour cell lines with the cDNA for CD40 conferred responsiveness to rhCD40L and anti-CD40 antibody. Finally, the presence of CD40 on the surface of carcinoma lines was found to be an important factor in the generation of tumour-specific T cell responses.

Aged mice exhibit greater mortality concomitant to increased brain and plasma TNF-alpha levels following intracerebroventricular injection of lipopolysaccharide

BACKGROUND

Age-related defects in the development of peripheral inflammatory responses have been observed in rodents and humans.

OBJECTIVE

We examined the effects of age on a centrally injected endotoxin-induced cytokine production and cellular activation in mice.

METHODS

Male C57BL/6J (B6) mice, C3H/HeN mice, and C3H/HeJ mice received an intracerebroventricular injection of lipopolysaccharide (LPS) and were sacrificed at various times (2, 4, 8 h) thereafter. ELISA for IL-1beta, IL-6, IL-12, and TNF-alpha were conducted on forebrain tissue homogenates as well as plasma samples, and lectin staining to detect activated microglia was prepared for selected brain slices.

RESULTS

Intracerebroventricular injection of LPS in B6 mice produced an age-associated increase in mortality which was paralleled with a significant increase in brain and plasma levels of TNF-alpha. AntiTNF-alpha- and IL-6-immunoreactive cells possessed macrophagelike morphologies and were observed along the LPS injection tract and scattered throughout the hilus of the dorsal hippocampus and cerebral cortices. This LPS-mediated response was found to be specific in that the LPS-hyporesponsive mouse strain (C3H/HeJ) failed to demonstrate significant brain or plasma levels of TNF-alpha after LPS administration compared to C3H/HeN mice.

CONCLUSION

These results suggest that the age-related increases in TNF-alpha production and mortality following the intracerebroventricular administration of LPS may be due to an increased endotoxin hypersensitivity of brain microglia/macrophages within aged animals.

Early increased chemokine expression and production in murine allogeneic skin grafts is mediated by natural killer cells

BACKGROUND

Increased expression of chemokine mRNA is observed in allogeneic but not syngeneic skin grafts 3-4 days after transplantation. The recipient cells mediating this early inflammatory response in allografts remain unidentified.

METHODS

Isogeneic and allogeneic skin grafts were transplanted to euthymic and athymic nude mice. mRNA expression and protein production of macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, and the murine homolog of Gro(alpha), i.e. KC, from graft homogenates retrieved 3-4 days posttransplantation was tested by Northern blot hybridization and ELISA. To deplete NK cells, recipients were treated with antiasialo GM1 (ASGM1) antisera or with anti-NK1.1 mAb before transplantation.

RESULTS

Expression of KC, MIP-1alpha, and MIP-1beta mRNA was equivalent in C57BL/6 allogeneic skin grafts and BALB/c isografts at day 2 posttransplant. At day 3 posttransplant, chemokine mRNA levels decreased in isografts but were maintained at high levels in the allografts. Increased early chemokine mRNA was also observed in C57BL/6, but not BALB/c++ grafts on BALB/c athymi(nu/nu) recipients. Treatment of allograft recipients with ASGM1 or with anti-NK1.1 antibody eliminated NK cells from the spleen and allograft infiltrating cell populations and decreased early chemokine mRNA levels in allografts 60-70%. Analyses of allograft homogenates indicated increased levels of KC, MIP-1alpha, and MIP-1beta protein at day 4 posttransplant that were decreased in recipients depleted of NK cells. Early chemokine mRNA levels were equivalent in isogeneic and semiallogeneic F1 grafts.

CONCLUSIONS

Early chemokine mRNA expression and protein production in allogeneic skin grafts is amplified by recipient natural killer (NK) cells. These results indicate a novel function for infiltrating NK cells in mediating early increased intra-allograft chemokine production and inflammation during the initiation of acute rejection.

Demonstration that platelet-activating factor is capable of activating mast cells and inducing a chemotactic response

Platelet-activating factor (PAF) is generated in a variety of inflammatory conditions in which mast cells accumulate. However, little is known about the ability of PAF to influence mast cell function directly. In this study we examine the ability of PAF to activate mast cells and regulate mast cell chemotaxis. PAF was found to induce intracellular calcium mobilization and chemotactic responses in both murine and human mast cells. PAF induced transient increases in intracellular Ca2+ concentrations with a 50% effective dose of 1 nM and induced significant migratory responses at PAF concentrations of 1 nM to 1 microM in the human leukaemia mast cell line (HMC-1). Using signal transduction inhibitors, both PAF-induced calcium mobilization and migration of mast cells were shown to require activation of pertussis toxin-sensitive G proteins. PAF-induced calcium and chemotactic responses were cross-desensitized by C5a. Together, these data demonstrate that PAF is capable of activating distinct signalling pathways in mast cells associated with calcium mobilization and cell migration; and that PAF may thus contribute to the regulation of mast cell responses and hyperplasia at sites of inflammation.

Treatment with tumor necrosis factor-alpha and granulocyte-macrophage colony-stimulating factor increases epidermal Langerhans' cell numbers in cancer patients

Dendritic cells (DCs) initiate primary and stimulate secondary T-cell responses. We conducted a phase I trial of tumor necrosis factor (TNF-alpha) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients with cancer to increase DCs in peripheral blood or skin based on in vitro data that showed that CD34(+) hematopoietic precursors require these cytokines to mature into functional antigen-presenting DCs. Eleven patients were treated for 7 days with GM-CSF, 125 microg/m(2) twice daily as subcutaneous injections, and TNF-alpha as a continuous infusion at dose levels of 25, 50, or 100 microg/m(2)/day. The maximum tolerated dose of TNF-alpha was 50 microg/m(2)/day with this dose of GM-CSF; dose-limiting toxicities occurred in both patients treated with 100 microg/m(2)/day. One became thrombocytopenic and the other had transient confusion. Epidermal Langerhans' cells were quantitated by S100 staining of skin biopsies and DC precursors in peripheral blood by colony-forming unit dendritic (CFU-dendritic) assays. S100-positive cells in the epidermis doubled after treatment (2.55 S100(+) cells/high-power field before treatment to 6.05 after treatment, p = 0.029). CFU-dendritic in peripheral blood increased after treatment in 3 colorectal cancer patients but not in 3 patients with melanoma. CD11c(+) or CD123(+), HLA-DR(bright), lineage-negative dendritic cell precursors were not increased in peripheral blood mononuclear cells. This trial demonstrates that treatment with TNF-alpha and GM-CSF can increase the number of DCs in the skin and the number of dendritic cell precursors in the blood of some patients with cancer. This approach may increase the efficacy of vaccination to tumor antigens in cancer patients.

Immunomodulatory role of C10 chemokine in a murine model of allergic bronchopulmonary aspergillosis

The immunomodulatory role of the chemokine C10 was explored in allergic airway responses during experimental allergic bronchopulmonary aspergillosis (ABPA). The intratracheal delivery of Asperigillus fumigatus Ag into A. fumigatus-sensitized mice resulted in significantly increased levels of C10 within the bronchoalveolar lavage, and these levels peaked at 48 h after A. fumigatus challenge. In addition, C10 levels in BAL samples were greater than 5-fold higher than levels of other chemokines such as monocyte-chemoattractant protein-1, eotaxin, and macrophage-inflammatory protein-1alpha. From in vitro studies, it was evident that major pulmonary sources of C10 may have included alveolar macrophages, lung fibroblasts, and vascular smooth muscle cells. Experimental ABPA was associated with severe peribronchial eosinophilia, bronchial hyperresponsiveness, and augmented IL-13 and IgE levels. The immunoneutralization of C10 with polyclonal anti-C10 antiserum 2 h before the intratracheal A. fumigatus challenge significantly reduced the airway inflammation and hyperresponsiveness in this model of ABPA, but had no effect on IL-10 nor IgE levels. Taken together, these data suggest that C10 has a unique role in the progression of experimental ABPA.

Immunomodulatory Role of C10 Chemokine in a Murine Model of Allergic Bronchopulmonary Aspergillosis

The immunomodulatory role of the chemokine C10 was explored in allergic airway responses during experimental allergic bronchopulmonary aspergillosis (ABPA). The intratracheal delivery of Asperigillus fumigatus Ag into A. fumigatus-sensitized mice resulted in significantly increased levels of C10 within the bronchoalveolar lavage, and these levels peaked at 48 h after A. fumigatus challenge. In addition, C10 levels in BAL samples were greater than 5-fold higher than levels of other chemokines such as monocyte-chemoattractant protein-1, eotaxin, and macrophage-inflammatory protein-1α. From in vitro studies, it was evident that major pulmonary sources of C10 may have included alveolar macrophages, lung fibroblasts, and vascular smooth muscle cells. Experimental ABPA was associated with severe peribronchial eosinophilia, bronchial hyperresponsiveness, and augmented IL-13 and IgE levels. The immunoneutralization of C10 with polyclonal anti-C10 antiserum 2 h before the intratracheal A. fumigatus challenge significantly reduced the airway inflammation and hyperresponsiveness in this model of ABPA, but had no effect on IL-10 nor IgE levels. Taken together, these data suggest that C10 has a unique role in the progression of experimental ABPA.

Mast cell migratory response to interleukin-8 is mediated through interaction with chemokine receptor CXCR2/Interleukin-8RB

To explore the role of chemokines in mast cell chemotaxis and accumulation at sites of inflammation, we first investigated the response of human mast cells to 18 different chemokines by induction of intracellular calcium mobilization in the human mast cell line, HMC-1. Only a subgroup of CXC chemokines defined by the conserved sequence motif glutamic acid-leucine-arginine (ELR) tripeptide motif, which included interleukin-8 (IL-8), growth-regulated oncogene alpha (GROalpha), neutrophil-activating peptide-2 (NAP-2), and epithelial cell-derived neutrophil activating peptide-78 (ENA-78), induced calcium flux in the cells. These observations suggested that the receptor CXCR2 (IL-8RB) should be expressed on the surface of these cells. Using the RNAse protection assay, CXCR2 mRNA, but not CXCR1 (IL-8RA) mRNA expression was detected in HMC-1 cells. Flow cytometry analysis documented the surface expression of CXCR2. A binding analysis performed with 125I-IL-8 determined that there were approximately 3,600 high affinity IL-8 binding sites per HMC-1 cell, with a calculated kd of 1.2 to 2 nmol/L. The activity of this receptor was further explored using IL-8, which was found to induce dose-dependent chemotactic and haptotactic responses in both HMC-1 cells and in vitro cultured human cord blood-derived mast cells. These results show the expression of functional CXCR2 receptors on the surface of human mast cells, which may play an important role in mast cell recruitment during the genesis of an inflammatory response.

Inhibition of human breast carcinoma growth by a soluble recombinant human CD40 ligand

CD40 is present on B cells, monocytes, dendritic cells, and endothelial cells, as well as a variety of neoplastic cell types, including carcinomas. CD40 stimulation by an antibody has previously been demonstrated to induce activation-induced cell death in aggressive histology human B-cell lymphoma cell lines. Therefore, we wanted to assess the effects of a recombinant soluble human CD40 ligand (srhCD40L) on human breast carcinoma cell lines. Human breast carcinoma cell lines were examined for CD40 expression by flow cytometry. CD40 expression could be detected on several human breast cancer cell lines and this could be augmented with interferon-gamma. The cell lines were then incubated with a srhCD40L to assess effects on in vitro growth. srhCD40L significantly inhibited the proliferation of the CD40(+) human breast cancer cell lines. This inhibition could also be augmented with interferon-gamma. Viability was also affected and this was shown to be due to increased apoptosis of the cell lines in response to the ligand. Treatment of tumor-bearing mice was then performed to assess the in vivo efficacy of the ligand. Treatment of tumor-bearing SCID mice with the ligand resulted in significant increases in survival. Thus, CD40 stimulation by its ligand directly inhibits human breast carcinoma cells in vitro and in vivo. These results suggest that srhCD40L may be of clinical use to inhibit human breast carcinoma growth.

Cocaine enhances brain endothelial adhesion molecules and leukocyte migration

Leukocyte infiltration of cerebral vessels in cocaine-associated vasculopathy suggests that cocaine may enhance leukocyte migration. We have investigated cocaine's effects on leukocyte adhesion in human brain microvascular endothelial cell (BMVEC) cultures and monocyte migration in an in vitro blood-brain barrier (BBB) model constructed with BMVEC and astrocytes. Cocaine (10(-5) to 10(-9) M) enhanced adhesion of monocytes and neutrophils to BMVEC. In the BBB model, cocaine (10(-4) to 10(-8) M) enhanced monocyte transmigration. Cocaine increased expression of endothelial adhesion molecules, intercellular adhesion molecule-1 (ICAM-1, CD54), vascular cell adhesion molecule-1 (VCAM-1), and endothelial leukocyte adhesion molecule-1 (ELAM-1) on BMVEC. The peak effect on ICAM-1 expression was between 6 and 18 h after treatment. ICAM-1 was increased by cocaine in BMVEC, but not in human umbilical vein endothelial cells, and the enhancement was greater in a coculture of BMVEC with monocytes. ICAM-1 expression was enhanced by a transcriptional mechanism. Polymyxin B inhibited up-regulation of adhesion molecules by LPS but not by cocaine. In LPS-activated BMVEC/monocyte coculture, cocaine increased secretion of tumor necrosis factor-alpha and interleukin-6. Taken together, these findings indicate that cocaine enhances leukocyte migration across the cerebral vessel wall, in particular under inflammatory conditions, but the effects are variable in different individuals. Cocaine's effects are exerted through a cascade of augmented expression of inflammatory cytokines and endothelial adhesion molecules. These could underlie the cerebrovascular complications of cocaine abuse.

Generation of artificial proteoglycans containing glycosaminoglycan-modified CD44. Demonstration of the interaction between rantes and chondroitin sulfate

All CD44 isoforms are modified with chondroitin sulfate (CS), while only those containing variably spliced exon V3 are modified with both CS and heparan sulfate (HS). The CS is added to a serine-glycine (SG) site in CD44 exon E5, while HS and CS are added to the SGSG site in exon V3. Site-directed mutagenesis and other molecular biology techniques were used to determine the minimal motifs responsible for the addition of CS and HS to CD44 (see accompanying paper (Greenfield, B., Wang, W.-C., Marquardt, H., Piepkorn, M., Wolff, E. A., Aruffo, A., and Bennett, K. L. (1999) J. Biol. Chem. 274, 2511-2517)). We have used this information to generate artificial proteoglycans containing the extracellular domain of the cell adhesion protein lymphocyte function-associated antigen-3 (LFA-3) (CD58) and CD44 motifs modified with CS or a combination of CS and HS. Analysis of the CD44-modified LFA-3 protein showed that it retains the ability to engage and trigger the function of its natural ligand CD2, resulting in T cell activation. In addition, the glycosaminoglycan-modified artificial proteoglycan is capable of binding the chemokine RANTES (regulated upon activation, normally T cell expressed and secreted) and delivering it to human T cells, resulting in enhanced T cell activation. These data demonstrate that artificial proteoglycans can be engineered with functional domains that have enhanced activity by codelivering glycosaminoglycan-binding molecules. The artificial proteoglycans were also used as a model system to explore the glycosaminoglycan binding properties of basic-fibroblast growth factor and the chemokine RANTES. While basic-fibroblast growth factor was shown to bind HS alone, this model revealed that RANTES binds not only HS, as has been demonstrated in the past, but also CS. Thus, artificial proteoglycans can be used for studying the glycosaminoglycan binding patterns of growth factors and chemokines and provide a means to manipulate the levels, types, and activity of glycosaminoglycan-binding proteins in vitro and in vivo.

Use of neuroendocrine hormones to promote reconstitution after bone marrow transplantation

A survey of the previous literature and the data shown here indicate that neuroendocrine hormones such as growth hormone and prolactin may be of potential clinical use after bone marrow transplantation (BMT) to promote hematopoietic and immune recovery. The amounts of hormones used in our model do not promote weight gain suggesting that their lymphohematopoietic actions were independent of their anabolic effects. While the hormones may not produce the same extent of immune/hematopoietic effects when compared to conventional hematopoietic and immune stimulating cytokines (i.e. IL-2 or G-CSF), their pleiotropic effects and limited toxicity after systemic administration makes them attractive to test in the post-BMT setting. However, more work needs to be performed to understand the mechanism(s) of their action, particularly with regard to T-cell function and development.

CD40 stimulation promotes human secondary immunoglobulin responses in HuPBL-SCID chimeras

Antibodies to CD40 have been demonstrated to promote B-cell growth and differentiation in vitro. In order to determine if CD40 stimulation could promote antigen-specific human immunoglobulin (Ig) production in vivo, we examined the effects of anti-human CD40 MoAb in an in vivo system where human peripheral blood lymphocytes (huPBL) were engrafted into mice with severe combined immune deficiency (SCID). The huPBL-SCID mice were then given various doses of diphtheria-tetanus toxoid (DT) vaccine and were examined for the presence of human DT-specific antibodies by ELISA. Surprisingly, treatment with anti-CD40 significantly lowered background DT responses versus untreated chimeras in unimmunized huPBL-SCID mice. However, after immunization, huPBL-SCID mice treated with anti-CD40 MoAb responded to a significantly greater extent in response to the vaccine compared with control huPBL-SCID mice, although total Ig levels were sometimes lower in anti-CD40-treated mice. The predominant Ig isotype induced after immunization was IgG. Thus, CD40 stimulation promotes human secondary IgG responses in huPBL-SCID mice. These data demonstrate that CD40 stimulation is capable of promoting antigen-specific human B-cell responses in vivo.

Differential effects of the absence of interferon-gamma and IL-4 in acute graft-versus-host disease after allogeneic bone marrow transplantation in mice

Graft-versus-host disease (GVHD), in which immunocompetent donor cells attack the host, remains a major cause of morbidity after allogeneic bone marrow transplantation (BMT). To understand the role of cytokines in the pathobiology of GVHD, we used cytokine knockout (KO) mice as a source of donor T cells. Two different MHC-disparate strain combinations were examined: BALB/c (H2(d)) donors into lethally irradiated C57BL/6 (H2(b)) recipients or C57BL/6 (H2(b)) donors into B10.BR (H2(k)) recipients. Donor cells were from mice in which either the interferon-gamma (IFN-gamma) or the IL-4 gene was selectively disrupted to understand the role of these cytokines in acute GVHD. In both strain combinations the same pattern was noted with regard to GVHD onset and morbidity. All mice exhibited the classic signs of acute GVHD: weight loss with skin, gut, and liver pathology resulting in morbidity and mortality. Surprisingly, donor cells obtained from mice lacking IFN-gamma gave rise to accelerated morbidity from GVHD when compared with cells from wild-type control donors. Similar results were obtained using normal donors when neutralizing antibodies to IFN-gamma were administered immediately after the BMT. These results suggest that IFN-gamma plays a role in protection from acute GVHD. In marked contrast, cells obtained from IL-4 KO mice resulted in protection from GVHD compared with control donors. Splenocytes from IFN KO mice stimulated with a mitogen proliferated to a significantly greater extent and produced more IL-2 compared with splenocytes obtained from IL-4 KO or control mice. Additionally, there was increased IL-2 production in the spleens of mice undergoing GVHD using IFN-gamma KO donors. These results therefore indicate, with regard to the TH1/ TH2 cytokine paradigm, the absence of a TH1-type cytokine can be deleterious in acute GVHD, whereas absence of a TH2 cytokine can be protective.

Molecular cloning of FKHRL1P2, a member of the developmentally regulated fork head domain transcription factor family

Here we report the expression of a fork head domain protein in human T helper cells. We cloned and characterized a fork head cDNA from human T helper cell mRNA using differential display RT-PCR. The cDNA contains a 546-nucleotide (nt) open reading frame (ORF) that codes for the carboxyl-terminal 180 amino acids (aa) of the recently identified fkhrl1 gene. This ORF does not contain the characteristic DNA-binding domain found in members of the forkhead protein family. In-vitro transcription/translation of this cDNA expressed a protein of approximately 20 kDa. We have generated antibodies that specifically immunoprecipitated the in-vitro-translated 20-kDa protein. This antibody also recognizes in human T lymphocytes a 70-kDa protein corresponding in size to that predicted for the fkhrl1 gene product. The mRNA levels for fkhrl1 is elevated in T helper-induced lymphocytes in comparison to PHA-stimulated T lymphocytes. Further characterization of FKHRL1 and its related family members should shed light on the transcriptional mechanisms of this fork head gene subfamily and their role in T helper cell differentiation and regulation of cell growth.

Infection with human immunodeficiency virus type 1 upregulates DNA methyltransferase, resulting in de novo methylation of the gamma interferon (IFN-gamma) promoter and subsequent downregulation of IFN-gamma production

The immune response to pathogens is regulated by a delicate balance of cytokines. The dysregulation of cytokine gene expression, including interleukin-12, tumor necrosis factor alpha, and gamma interferon (IFN-gamma), following human retrovirus infection is well documented. One process by which such gene expression may be modulated is altered DNA methylation. In subsets of T-helper cells, the expression of IFN-gamma, a cytokine important to the immune response to viral infection, is regulated in part by DNA methylation such that mRNA expression inversely correlates with the methylation status of the promoter. Of the many possible genes whose methylation status could be affected by viral infection, we examined the IFN-gamma gene as a candidate. We show here that acute infection of cells with human immunodeficiency virus type 1 (HIV-1) results in (i) increased DNA methyltransferase expression and activity, (ii) an overall increase in methylation of DNA in infected cells, and (iii) the de novo methylation of a CpG dinucleotide in the IFN-gamma gene promoter, resulting in the subsequent downregulation of expression of this cytokine. The introduction of an antisense methyltransferase construct into lymphoid cells resulted in markedly decreased methyltransferase expression, hypomethylation throughout the IFN-gamma gene, and increased IFN-gamma production, demonstrating a direct link between methyltransferase and IFN-gamma gene expression. The ability of increased DNA methyltransferase activity to downregulate the expression of genes like the IFN-gamma gene may be one of the mechanisms for dysfunction of T cells in HIV-1-infected individuals.

Opiates transdeactivate chemokine receptors: delta and mu opiate receptor-mediated heterologous desensitization

An intact chemotactic response is vital for leukocyte trafficking and host defense. Opiates are known to exert a number of immunomodulating effects in vitro and in vivo, and we sought to determine whether they were capable of inhibiting chemokine-induced directional migration of human leukocytes, and if so, to ascertain the mechanism involved. The endogenous opioid met-enkephalin induced monocyte chemotaxis in a pertussis toxin-sensitive manner. Met-enkephalin, as well as morphine, inhibited IL-8-induced chemotaxis of human neutrophils and macrophage inflammatory protein (MIP)-1alpha, regulated upon activation, normal T expressed and secreted (RANTES), and monocyte chemoattractant protein 1, but not MIP-1beta-induced chemotaxis of human monocytes. This inhibition of chemotaxis was mediated by delta and micro but not kappa G protein-coupled opiate receptors. Calcium flux induced by chemokines was unaffected by met-enkephalin pretreatment. Unlike other opiate-induced changes in leukocyte function, the inhibition of chemotaxis was not mediated by nitric oxide. Opiates induced phosphorylation of the chemokine receptors CXCR1 and CXCR2, but neither induced internalization of chemokine receptors nor perturbed chemokine binding. Thus, inhibition of chemokine-induced chemotaxis by opiates is due to heterologous desensitization through phosphorylation of chemokine receptors. This may contribute to the defects in host defense seen with opiate abuse and has important implications for immunomodulation induced by several endogenous neuropeptides which act through G protein-coupled receptors.

Identification and characterization of small molecule functional antagonists of the CCR1 chemokine receptor

The CC chemokines macrophage inflammatory protein-1alpha (MIP-1alpha) and RANTES (regulated on activation normal T cell expressed) have been implicated in rheumatoid arthritis and multiple sclerosis. Since their effects are mediated through the CCR1 chemokine receptor, we set up a small molecule CCR1 antagonist program to search for inhibitors. Through high capacity screening we discovered a number of 4-hydroxypiperidine compounds with CCR1 antagonist activity and report their synthesis and in vitro pharmacology here. Scatchard analysis of the competition binding data revealed that the compounds had Ki values ranging from 40 to 4000 nM. The pharmacological profile of the most potent member of this series, compound 1 (2-2-diphenyl-5-(4-chlorophenyl)piperidin-lyl)valeronitri te), was further evaluated. Compound 1 showed concentration-dependent inhibition of MIP-1alpha-induced extracellular acidification and Ca2+ mobilization demonstrating functional antagonism. When given alone, the compound did not elicit any responses, indicating the absence of intrinsic agonist activity. Compound 1 inhibited MIP-1alpha- and RANTES-induced migration in peripheral blood mononuclear cells in a dose-responsive manner. Selectivity testing against a panel of seven transmembrane domain receptors indicated that compound 1 is inactive on a number of receptors at concentrations up to 10 microM. This is the first description of CCR1 receptor antagonists that may be useful in the treatment of chronic inflammatory diseases involving MIP-1alpha, RANTES, and CCR1.

Novel Role of Transmembrane SCF for Mast Cell Activation and Eotaxin Production in Mast Cell-Fibroblast Interactions

Mast cell activation can be induced by multiple mechanisms, including IgE-, complement-, and stem cell factor (SCF)-mediated pathways. In addition, the interaction of mast cells with particular cell populations, such as fibroblasts, have also demonstrated increased mast cell reactivity. In these studies, we have investigated the role of fibroblast-mast cell interaction for induction of histamine release and chemokine production and the specific role of SCF during this interaction. Primary pulmonary fibroblast cell lines were grown in culture and used throughout these studies. Mast cells were grown in parallel with fibroblasts by incubation of bone marrow cells with SCF and IL-3. During mast cell-fibroblast coculture, increased histamine release could be attenuated either by separation of the cell populations using a Trans-Well setup, which did not allow cellular contact, or by specific anti-SCF Ab. In addition, a significant increase in eotaxin, a potent eosinophil-specific C-C chemokine, was also observed during fibroblast-mast cell interaction. The production of eotaxin was cell contact dependent and could be inhibited using an anti-SCF Ab or specific antisense therapy. SCF was constitutively produced from fibroblasts in its transmembrane form and could be induced by TNF. SCF-coated plates induced significant mast cell-derived eotaxin production, whereas soluble SCF induced little or no eotaxin, suggesting a necessity for receptor cross-linking for activation. These studies indicate that fibroblast-mast cell contact plays a role in exacerbation of histamine release and eotaxin production.

Novel role of transmembrane SCF for mast cell activation and eotaxin production in mast cell-fibroblast interactions

Mast cell activation can be induced by multiple mechanisms, including IgE-, complement-, and stem cell factor (SCF)-mediated pathways. In addition, the interaction of mast cells with particular cell populations, such as fibroblasts, have also demonstrated increased mast cell reactivity. In these studies, we have investigated the role of fibroblast-mast cell interaction for induction of histamine release and chemokine production and the specific role of SCF during this interaction. Primary pulmonary fibroblast cell lines were grown in culture and used throughout these studies. Mast cells were grown in parallel with fibroblasts by incubation of bone marrow cells with SCF and IL-3. During mast cell-fibroblast coculture, increased histamine release could be attenuated either by separation of the cell populations using a Trans-Well setup, which did not allow cellular contact, or by specific anti-SCF Ab. In addition, a significant increase in eotaxin, a potent eosinophil-specific C-C chemokine, was also observed during fibroblast-mast cell interaction. The production of eotaxin was cell contact dependent and could be inhibited using an anti-SCF Ab or specific antisense therapy. SCF was constitutively produced from fibroblasts in its transmembrane form and could be induced by TNF. SCF-coated plates induced significant mast cell-derived eotaxin production, whereas soluble SCF induced little or no eotaxin, suggesting a necessity for receptor cross-linking for activation. These studies indicate that fibroblast-mast cell contact plays a role in exacerbation of histamine release and eotaxin production.

Similar levels of human immunodeficiency virus type 1 replication in human TH1 and TH2 clones

Studies on the development and function of CD4+ TH1 and TH2 cells during the progression to AIDS may increase the understanding of AIDS pathogenesis. The preferential replication of human immunodeficiency virus (HIV) in either TH1 or TH2 cells could alter the delicate balance of the immune response. TH1 (gamma interferon [IFN-gamma] positive, interleukin-4 [IL-4] and IL-5 negative) and TH2 (IFN-gamma negative, IL-4 and IL-5 positive) clones, developed from several healthy donors, pedigreed by reverse transcriptase PCR (RT-PCR) and enzyme linked immunosorbent assay have similar levels of cell surface expression of CD4 and several chemokine receptor cofactors necessary for viral entry. After activation by specific antigens and infection with T-cell-tropic strains of HIV type 1 (HIV-1), TH1 and TH2 clones showed similar levels of viral entry and reverse transcription. At days 3 through 14 postinfection, HIV replicated to similar levels in several TH1 and TH2 clones as measured by release of HIV p24 and total number of copies of gag RNA/total cell RNA as measured by RT-PCR. When values were normalized for viable cell number in three clones of each type, there was up to twofold more HIV RNA in TH1 than TH2 cells. In addition, several primary monocytotropic HIV-1 strains were able to replicate to similar levels in TH1 and TH2 cells. These studies suggest that the importance of TH1 and TH2 subsets in AIDS pathogenesis transcends clonal differences in their ability to support HIV replication.

Sticky and smelly issues: lessons on tumour cell and leucocyte trafficking, gene and immunotherapy of cancer

The Second Meeting of the British Society for Immunology Tumour Immunology Affinity Group (TIAG) took place at King's College (London, UK) on 17-18 June 1997 and brought together over 100 tumour immunologists from the UK and abroad. In contrast to previous meetings the focus of the meeting was on the role of adhesion in immunosurveillance and tumour dissemination. In addition, recent achievements in the areas of chemokines, cytotoxic T-lymphocyte (CTL) and natural killer (NK) cells, co-stimulation, gene and adoptive immunotherapy were also addressed. The purpose of this report is to outline current trends in tumour immunology.