Cytokine gene expression after allogeneic bone marrow transplantation

Cytokines produced by T lymphocytes, monocytes/macrophages, and fibroblasts play a central role in the immune response and in the development of graft-versus-host disease (GVHD). Also, it has been reported that dysregulated production of cytokines maybe the primary mediator of clinical manifestation of acute GVHD. Regarding cytokine gene expression after human allogeneic bone marrow transplantation (allo BMT), we have demonstrated increased IL-1 beta, IL-6, and TNF-alpha mRNA expression in peripheral blood mononuclear cells during the development of acute and chronic GVHD and that the degree of the increase was dependent on the severity of the disease. Furthermore, overexpression of these cytokine mRNAs could be detected before the clinical manifestations of GVHD developed. In contrast, IL-2 mRNA expression was not detected in peripheral blood mononuclear cells in GVHD patients. On the other hand, we have reported that increased mRNA expression and protein product of IL-2 and IFN-gamma were evident in the mixed lymphocyte culture of the cases who developed severe lethal transplantation-related complications. Therefore, the detection of increased IL-2 and IFN-gamma gene expression in MLC appeared to be useful for predicting transplantation-related complications in BMT patients. Furthermore, we found increased IL-2 receptor alpha subunit mRNA expression in the peripheral blood mononuclear cells during GVHD. These findings may indicate the important role of inflammatory cytokines such as IL-1 beta, IL-6 and TNF-alpha in the development of the clinical manifestation of GVHD and also may be indicative of the important role of IL-2 and the IL-2 receptor in allo response perhaps mainly as an autocrine effect.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effects of retinoic acid on the adhesion and motility of metastatic human lung cancer cell subline (PGCL3)]

Effects of all-trans Retinoic Acid (RA) on the adhesion and motility of metastatic human lung cancer cell subline (PGCL3) were observed in vitro. The results showed that treatment of PGCL3 with RA for 5 days decreased the adhesion of cells to laminin substrate and the migrative ability through the polycarbonate filter of Boyden chamber, and those inhibitory effects became more obvious with the increase of RA concentration. Further investigation by DNA-RNA dot blot hybridization and immunohistochemistry denoted that RA-treated PGCL3 cells expressed lower level of 67-KD LN-R compared to untreated cells. The data from DNA-RNA dot blot hybridization also showed that RA could reduce the expression of AMF-R significantly. These results raise the possibility that the previously reported suppression by RA of PGCL3 invasion and metastasis may be related to suppression of cell adhesion and motility resulting from the decreased expression of the LN-R and AMF-R respectively.

Growth and differentiation of the human megakaryoblastic cell line (ELF-153): a model for early stages of megakaryocytopoiesis

ELF-153 is a cell line that has been established from a patient with a poorly differentiated acute myeloid leukemia associated with an acute myelofibrosis. A majority of cells had a blast morphology with the phenotype of a myeloid hematopoietic progenitor, ie, CD34+, CD33+, CD13+, HLA-DR+, but CD38-, and the remaining cells (5% to 10%) expressed platelet restricted proteins such as CD41, CD42, CD36, CD61, and von Willebrand factor; some of them were polyploid (up to 32N) and exhibited demarcation membranes and alpha granules. No erythroid or other lineage-specific markers were detected. Proliferation of ELF-153 cells was highly stimulated by interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor and to a lesser extent by stem cell factor and IL-6. In contrast, the cell line did not respond to erythropoietin, leukemia inhibitory factor, IL-7, IL-11, granulocyte colony-stimulating factor, and basic fibroblast growth factor. ELF-153 cells could be separated by flow cytometry into three discrete cell populations (CD34+/CD61-, CD34+/CD61+, and CD34-/CD61+) with different proliferative and endomitotic properties corresponding to distinct stages of the mega karyocyte (MK) differentiation. This MK differentiation, which involved a minority of ELF-153, could be increased in the presence of 5-azacytidine and phorbol ester, but could not be significantly modified by growth factors. By contrast, cytochalasin B dramatically induced polyploidization without differentiation. It is noteworthy that association of 5-azacytidine to cytochalasin B dramatically induced the production of polyploid MK cells. To understand the molecular mechanisms underlying this MK differentiation, the expression of GATA-1 and GATA-2 was investigated in subpopulations of ELF-153. A high level of GATA-1 and GATA-2 mRNA was only present in the CD61+ cells. Therefore, these two transactivating factors may play an important role in the MK differentiation of ELF-153. We conclude that ELF-153 might be an important tool to investigate the mechanisms by which transcription factors control differentiation of MK progenitors.

Major changes in the expression of the mRNAs for cholinergic differentiation factor/leukemia inhibitory factor and its receptor after injury to adult peripheral nerves and ganglia

The neuropoietic cytokine cholinergic differentiation factor/leukemia inhibitory factor (CDF/LIF) acts as a trophic factor, enhancing neuronal survival, and as a differentiation factor, altering neuronal gene expression. There is also evidence that its plays a role in the response of adult neural tissue to injury. We have examined this possibility further in rats by analyzing changes in the levels of mRNAs for CDF/LIF and its two receptor subunits in response to peripheral nerve damage in culture and in vivo. Using a quantitative RNase protection assay, we find that CDF/LIF mRNA increases dramatically (176-fold) in adult, but not neonatal, sympathetic ganglia and in adult dorsal root ganglia and sciatic nerve after organ culture for 24 hr. This mRNA is clearly detectable by in situ hybridization only in the nonneuronal cells of these structures. When the sciatic nerve is transected in vivo, CDF/LIF mRNA increases significantly in the regions immediately proximal and distal to the lesion site. The mRNA for the ligand binding subunit of the CDF/LIF receptor complex decreases somewhat upon culture and nerve section. The dramatic rise in CDF/LIF mRNA after nerve injury is further evidence that this cytokine is involved in the response to damage, a function that overlaps with its postulated role in wounding or infection in several nonneural tissues.

Selective expression of the murine homologue of the G-protein-coupled receptor BLR1 in B cell differentiation, B cell neoplasia and defined areas of the cerebellum

The Burkitt's lymphoma receptor 1 (BLR1) identified initially in Burkitt lymphoma cells has been the first member of the superfamily of G-protein-coupled receptors with a lymphocyte specific expression pattern. BLR1 shows significant relationship to receptors for chemokines (IL-8, MIP-1 beta) and neuropeptides. The gene encoding the murine homologue of the human BLR1 receptor was isolated and used to study its tissue-specific expression. Blr-1 consists of two exons encoding a protein of 374 amino acid residues which shows 83% identity with the human homologue. Screening of normal tissues of adult BALB/c mice revealed that blr-1-specific RNA is detected consistently at low levels in secondary lymphatic organs. The blr-1 gene is expressed regularly and strongly in lymphomas of mature B cells but not in plasmacytomas. SCID mice deficient in the development of mature B cells have strongly reduced levels of blr-1-specific RNA in the spleen. Cytokine mediated induction (IL4, IL6) of terminal differentiation of resting B cells towards Ig-secreting plasma cells completely downregulates expression of blr-1. RNA in situ hybridization using brain sections demonstrates blr 1 transcription in the granule and Purkinje cell layer of the cerebellum. The precise delineation of the restricted expression pattern of the blr-1 gene will support the identification of its ligand and may provide a clue to understand how BLR1 exerts its biological function within the immune and nervous system.

Transmembrane topology of the lymphocyte-specific G-protein-coupled receptor BLR1: analysis by flow cytometry and immunocytochemistry

The blr1 gene encodes the first member of the superfamily of G-protein-coupled receptors showing a lymphocyte- and differentiation-specific expression pattern. To study the synthesis of the BLR1-protein and to characterize the receptor we fused its coding region to a sequence derived from human c-MYC allowing the detection of the corresponding fusion protein by an anti-myc-antibody. Expression of the epitope-tagged BLR1 in human embryonic kidney 293 cells to high levels showed an apparent molecular mass for BLR1 of 50 kDa. This is reduced to 40 kDa following treatment of the cells with tunicamycin indicating the presence of N-linked glycosylation. Furthermore expression of amino- and carboxyl-terminally tagged BLR1 demonstrated that BLR1 is an integral protein of the plasma membrane inserted therein in the predicted orientation. Using this efficient expression system we generated a monoclonal antibody (mAb 8B2) against human BLR1. Flow cytometric analysis of peripheral blood lymphocytes confirms the lymphocyte-specific expression of BLR1. The highly efficient expression of BLR1 in 293 cells and the generated mAb offers a powerful tool for further characterization of this receptor and analysis of its function on lymphocytes and during B-cell development.

Molecular cloning and functional expression of two monocyte chemoattractant protein 1 receptors reveals alternative splicing of the carboxyl-terminal tails

Monocyte chemoattractant protein 1 (MCP-1) is a member of the chemokine family of cytokines that mediate leukocyte chemotaxis. The potent and specific activation of monocytes by MCP-1 may mediate the monocytic infiltration of tissues in atherosclerosis and other inflammatory diseases. We have isolated cDNAs that encode two MCP-1-specific receptors with alternatively spliced carboxyl tails. Expression of the receptors in Xenopus oocytes conferred robust mobilization of intracellular calcium in response to nanomolar concentrations of MCP-1 but not to related chemokines. The MCP-1 receptors are most closely related to the receptor for the chemokines macrophage inflammatory protein 1 alpha and RANTES (regulated on activation, normal T expressed and secreted). The identification of the MCP-1 receptor and cloning of two distinct isoforms provide powerful tools for understanding the specificity and signaling mechanisms of this important chemokine.

Expression of the Duffy antigen in K562 cells. Evidence that it is the human erythrocyte chemokine receptor

The human malarial parasite Plasmodium vivax invades erythrocytes by binding to a cell surface protein identified as the Duffy blood group antigen. The molecular properties of the Duffy antigen, which was recently cloned, are very similar to those of a chemokine binding protein known as the human erythrocyte chemokine receptor. This has led to the suggestion that these two molecules are the same protein. To further investigate the suspected double identity of the Duffy antigen we have transfected it into a human erythroleukemic cell line, K562. Cells stably expressing the Duffy antigen were isolated and used to characterize the protein. K562 cells transfected with the Duffy antigen displayed specific 125I-melanoma growth-stimulating activity (MGSA) binding while mock transfected cells did not. Comparison of 125I-MGSA binding to the Duffy antigen and the human erythrocyte chemokine receptor showed that the specific 125I-MGSA binding to both proteins was displaced by excess unlabeled MGSA, interleukin-8, RANTES, monocyte chemotactic peptide-1, and platelet factor 4, but not by macrophage inflammatory protein-1 alpha or -1 beta. Scatchard analysis of competition binding studies with these unlabeled chemokines revealed high affinity binding to the Duffy antigen with KD binding values of 24 +/- 4.9, 20 +/- 4.7, 41.9 +/- 12.8, and 33.9 +/- 7 nM for MGSA, interleukin-8, RANTES, and monocyte chemotactic peptide-1, respectively. A monoclonal antibody, Fy6, to the Duffy antigen inhibited 125I-MGSA binding to K562 cells expressing the Duffy antigen. Cell membranes from K562 cells permanently expressing the Duffy antigen were chemically cross-linked with 125I-MGSA. SDS-polyacrylamide gel electrophoresis analysis of the cross-linked products showed covalent incorporation of radiolabeled MGSA into a protein of molecular mass 47 kDa, and cross-linking was inhibited in the presence of unlabeled MGSA. These studies provide evidence that the Duffy blood group antigen is the same protein as the human erythrocyte chemokine receptor.

Topological characterization of the lymphoid-specific seven transmembrane receptor BLR1 by epitope-tagging and high level expression

We have tagged the human lymphocyte-specific G-protein-coupled receptor BLR1 either with an amino-terminal or a carboxyl-terminal epitope-tag recognized by an anti-MYC monoclonal antibody. Flow cytometry was used to determine the efficiency of transient transfections and to establish human embryonic kidney 293 cell clones showing stable high level expression of BLR1. Analysis of permeabilized versus non-permeabilized transfected 293 cells demonstrated that BLR1 is an integral plasma membrane protein, topologically oriented therein as predicted for other members of this class of seven pass membrane receptors. In addition, BLR1 was expressed in 293 cells to high levels as a glycosylated membrane protein. The easily detectable and assayable expression of tagged G-protein-coupled receptors, as exemplified for BLR1 in 293 cells, provides a suitable system for further functional studies and offers an efficient screening tool for the identification of receptor-specific antibodies, ligands, or receptor-associated proteins.

Pregnancy associated increase in mRNA for soluble D-factor/LIF receptor in mouse liver

We examined the distribution of mRNAs for differentiation-stimulating factor (D-factor)/leukemia inhibitory factor (LIF) receptor in various mouse tissues by Northern blotting. A mouse cDNA fragment encoding the D-factor receptor was prepared by the RT-PCR method using human cDNA sequences as primers. The smallest mRNA (3 kb) was present in the liver, but not detectable in other tissues examined. Larger mRNAs (5 and 10 kb) were present in the placenta and the M1 cells, and also detectable in the liver, kidney, heart, lung, brain and embryos. Expression of 3 kb mRNA in the liver increased during pregnancy, being 20 times the initial level on day 15. D-factor receptor cDNAs were isolated from a cDNA library prepared from the liver of a pregnant mouse. Most of the cDNA clones encoded a soluble receptor. A cDNA probe specific for the cellular receptor did not hybridize with 3 kb mRNA in the liver. These results suggest that 3 kb mRNA encodes a soluble D-factor receptor and that the liver is the primary site of synthesis of this soluble receptor.

A general method for screening mAbs specific for G-protein coupled receptors as exemplified by using epitope tagged BLR1-transfected 293 cells and solid-phase cell ELISA

Monoclonal antibodies (mAb) against G-protein coupled receptors are rare. In this study we describe a cell ELISA-based screening system for monoclonal antibodies specific for the G-protein coupled receptor BLR1 (Eur. J. Immunol. 1992. 22:2795) using human embryonic kidney 293 cells transfected with a modified human BLR1 cDNA directing the synthesis of an epitope tagged BLR1 protein. Lou/C rats were immunized with BLR1 transfected, tagged 293 cells and after fusion of spleen cells with X63 Ag8.653 myeloma cells supernatants were tested for BLR1 specific antibodies by comparing the binding to BLR1 transfected 293 cells and to untransfected control cells immobilised on poly-L-lysine coated microtiter plates. Cells were fixed with 2% paraformaldehyde and permeabilized using digitonin in order to allow binding of mAb directed against intracellular epitopes. This mild fixation retained excellent morphology of 293 cells and allowed reliable binding to the trays. Screening of approximately 2500 supernatants identified 19 antibodies binding to BLR1 transfected 293 cells but not to control 293 cells. One of these mAb specifically bound to the G-protein coupled receptor BLR1.

Studies of binding and internalization of human recombinant monocyte chemotactic and activating factor (MCAF) by monocytic cells

Recombinant human monocyte chemotactic and activating factor (MCAF) was iodinated and specific binding sites for this cytokine were detected on human peripheral blood monocytes, the monocytic leukemia cell line THP-1, and on PMA-differentiated HL60 and U937 cell lines. The binding sites were specific for MCAF since other polypeptide cytokines and the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (fMLP) failed to compete for 125I-rhMCAF binding. Steady-state binding experiments at 4 degrees C revealed the presence of 13,000 and 18,000 receptor sites/cell on monocytes and THP-1 cells with Kd values of 22.5 nM and 25.7 nM, respectively. Compared to a human natural MCAF, rhMCAF was less potent in inducing maximal monocyte migration. Human natural MCAF similarly competed more efficiently for 125I-rhMCAF binding than unlabelled rhMCAF. The ligand-receptor association was highly temperature-dependent, with maximal ligand uptake at 37 degrees C accompanied by internalization of the ligand-receptor complexes. The internalized 125I-MCAF was progressively degraded and released into the culture medium starting at 30 min. Lysosomotropic ammonium chloride could inhibit the degradation of this ligand suggesting the involvement of lysosomal enzymes in the proteolytic digestion. Incubation with cycloheximide did not block the rapid reappearance of MCAF receptors within 20 min on the cell surface indicative of receptor recycling rather than new protein synthesis. These data indicate that monocytic cells express specific receptors for rhMCAF which can be dynamically regulated by MCAF.