Long-term culture system for selective growth of human B-cell progenitors.

We describe a simple reproducible system for enrichment and long-term culture of human B-cell progenitors. Enriched CD34+ cord blood mononuclear cells are seeded onto a murine stromal cell line to establish a biphasic culture system. These cultures are characterized by transient growth of myeloid cells followed by outgrowth of cells highly enriched for early B-cell progenitors. Cultures consisting of > 90% early B-lineage cells [expressing CD10, CD19, CD38, and CD45 but lacking CD20, CD22, CD23, and surface IgM] are maintained for > 12 weeks without growth factor addition. Cells remain predominantly germ line at the immunoglobulin locus and express only low levels of cytoplasmic mu chain, terminal deoxynucleotidyltransferase, and recombination-activating gene 1 product. They are unresponsive to the pre-B-cell growth factors interleukin 7 or stem cell factor, or both, suggesting that growth support is provided by a cross-reactive murine stromal cell factor. Cultured B-cell progenitors are generated in large numbers ( > 10(8) cells from a typical cord blood specimen) suitable for use in biochemical analysis and gene-transfer studies. This system should be useful for study of normal and abnormal early human B-lymphopoiesis.

Isolation of unknown genes from human bone marrow by differential screening and single-pass cDNA sequence determination.

A cDNA sequencing project was initiated to characterize gene expression in human bone marrow and develop strategies to isolate novel genes. Forty-eight random DNAs from total human bone marrow were subjected to single-pass DNA sequence analysis to determine a limited complexity of mRNAs expressed in the bone marrow. Overall, 8 cDNAs (17%) showed no similarity to known sequences. Information from DNA sequence analysis was used to develop a differential prescreen to subtract unwanted cDNAs and to enrich for unknown cDNAs. Forty-eight cDNAs that were negative with a complex probe were subject to single-pass DNA sequence determination. Of these prescreened cDNAs, the number of unknown sequences increased to 23 (48%). Unknown cDNAs were also characterized by RNA expression analysis using 25 different human leukemic cell lines. Of 13 unknown cDNAs tested, 10 were expressed in all cell types tested and 3 revealed a hematopoietic lineage-restricted expression pattern. Interestingly, while a total of only 96 bone marrow cDNAs were sequenced, 31 of these cDNAs represent sequences from unknown genes and 12 showed significant similarities to sequences in the data bases. One cDNA revealed a significant similarity to a serine/threonine-protein kinase at the amino acid level (56% identity for 123 amino acids) and may represent a previously unknown kinase. Differential screening techniques coupled with single-pass cDNA sequence analysis may prove to be a powerful and simple technique to examine developmental gene expression.

Identification and molecular cloning of a soluble human granulocyte-macrophage colony-stimulating factor receptor.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) plays an important role in hematopoiesis and host defense via interaction with specific cell-surface receptors in target tissues. We identified a truncated, soluble form of the low-affinity GM-CSF receptor (GMR) in chorio-carcinoma cells. Low-affinity GMR cDNAs encoding both the membrane-bound and soluble receptors were obtained by PCR using primers corresponding to the published sequence. Clones encoding the soluble receptor were identical in sequence to the membrane-bound form but contained a 97-nucleotide internal deletion. The amino acid sequence of this deleted cDNA predicts a protein that lacks the 84 C-terminal amino acids of the membrane-bound receptor, including the transmembrane and cytoplasmic domains, and contains 16 different amino acids at its C terminus. Expression of the soluble GMR cDNA in murine psi-AM cells as well as GM-CSF-dependent myeloid 32Dc13 cells produced a secreted protein that retained its capacity to bind GM-CSF in solution. RNase protection analysis indicates that this variant cDNA is derived from a naturally occurring mRNA. Soluble receptors have been identified for several other hematopoietin receptors and may be a general feature of this class. The striking similarity between the soluble form of the GMR and other hematopoietin receptors suggests that soluble binding proteins may play an important role in regulating the broad spectrum of biological responses mediated by these cytokines.

Macrophage-active colony-stimulating factors enhance human immunodeficiency virus type 1 infection in bone marrow stem cells.

To define the relationship between human immunodeficiency virus type 1 (HIV-1) infection in hematopoietic stem cells and virus production by their progeny, we performed kinetic studies infecting bone marrow (BM) stem cells and culturing them in the presence of hematopoietic growth factors. CD34-positive (CD34+), CD4-negative (CD4-) BM cells were isolated and infected in vitro with the monocytotropic HIV-1JR-FL strain or the laboratory-maintained HTLV-IIIB strain at a high multiplicity of infection. The cells were susceptible to productive infection only with HIV-1JR-FL, and virus production as measured by p24 protein release was markedly increased (more than fivefold) in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3). Macrophage CSF (M-CSF) was less stimulatory and granulocyte CSF (G-CSF) had no effect on virus production. Virus production coincided with proliferation of mononuclear phagocytes but was not related to granulocytic proliferation in G-CSF-treated BM cultures. Although peak virus production from GM-CSF-treated macrophages occurred 2 to 3 weeks after infection, peak virus production in infected stem cells was observed 5 to 6 weeks after. Enhancement in virus production had a more rapid onset when CD34+/CD4- cells were cultured in the presence of both GM-CSF and IL-3 for 7 or 14 days. Under these conditions there was a 10-fold enhancement in virus production after 7 days of preincubation and a 50-fold enhancement after 14 days. These data indicate that while the stem cell compartment may be susceptible to infection with a monocytotropic HIV-1 strain, productive and sustained infection is realized only after macrophage differentiation. The lack of effect of G-CSF on virus production is likely because of the limited effect of this hematopoietin on mononuclear phagocyte generation and function.

Human granulocyte colony-stimulating factor: biologic activities and receptor characterization on hematopoietic cells and small cell lung cancer cell lines.

Human granulocyte colony-stimulating factor (G-CSF) is a regulatory glycoprotein that stimulates the production of neutrophilic granulocytes from committed hematopoietic progenitor cells both in vitro and in vivo. In this report, we show that biosynthetic (recombinant) human G-CSF enhances colony formation by normal human bone marrow and the human myeloid leukemic cell lines, HL-60 and KG-1, as well as nonhematopoietic small cell lung cancer lines, H128 and H69. G-CSF also modulates multiple differentiated functions of human neutrophils, including enhanced oxidative metabolism in response to f-Met-Leu-Phe (f-MLP), increased antibody-dependent cell-mediated cytotoxicity (ADCC), and augmented arachidonic acid release in response to ionophore and chemotactic agents. These effects are all maximal at a concentration of 100 to 500 pmol/L. Using 125I-labeled recombinant human G-CSF, high affinity binding sites were identified on human neutrophils, the myeloid leukemia cell lines KG-1 and HL-60, and the small cell carcinoma cell lines, H128 and H69. G-CSF receptor numbers ranged between 138 and 285 sites per cell with a kd of 77 to 140 pmol/L, consistent with the concentrations of G-CSF that elicit biologic responses in vitro. Decreased specific binding of 125l-G-CSF by human neutrophils was consistently observed in the presence of excess unlabeled human granulocyte-macrophage colony-stimulating factor (GM-CSF), suggesting competition or down modulation by GM-CSF of the G-CSF receptor.

Inhibition of colony-stimulating factor-1 activity by monoclonal antibodies to the human CSF-1 receptor.

Four of 12 monoclonal antibodies (MoAbs) directed to different epitopes in the extracellular domain of the human colony-stimulating factor-1 receptor (CSF-1R, the c-fms proto-oncogene product) specifically inhibit CSF-1 binding to receptor-bearing cells. All four antibodies abrogated CSF-1-dependent colony formation by human bone marrow-derived macrophage precursors and by mouse NIH-3T3 cells expressing a transduced human c-fms gene. In addition, one of these antibodies (designated MoAb 2-4A5) interfered with the ligand-independent proliferation of NIH-3T3 cells transformed by an oncogenic, mutant c-fms allele. Unlike CSF-1 itself, neither MoAb 2-4A5 nor the other three inhibitory antibodies (MoAbs 12-2D6, 12-3A1, and 12-3A3) induced CSF-1R internalization or degradation. These antibodies should prove useful not only for identifying and quantitating CSF-1R on receptor-bearing cells but for abrogating specific receptor signals that govern the proliferation and survival of human mononuclear phagocytes.

Nonhematopoietic tumor cells express functional GM-CSF receptors.

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates the colony growth of myeloid progenitors in semisolid media, and enhances the function of mature effector cells, including neutrophils, monocytes, and eosinophils. Small cell carcinoma lines (SCCL) have properties of amine precursor uptake and decarboxylation (APUD) cells and express high levels of the enzyme, L-aromatic amino acid decarboxylase. We looked for possible expression of GM-CSF receptors on nonhematopoietic cells and found specific high-affinity binding of human GM-CSF to SCCL and to the SV40-transformed African green monkey kidney cell line, COS. The small cell carcinoma lines responded to GM-CSF with enhanced proliferation, and both small cells and COS cells were found to express authentic 84,000 dalton GM-CSF receptor protein. These findings indicate that nonhematopoietic cells can bind and respond to GM-CSF, suggesting additional biological activities as well as the possibility of tumor responses when GM-CSF is used therapeutically in humans. Since preliminary clinical trials using CSFs as adjunctive treatment in patients with solid tumors are underway, it will be important to consider the possible responsiveness of nonhematopoietic tumor cells to CSFs.

T cell lines established from multiple sclerosis cerebrospinal fluid T cells using human retroviruses.

Cerebrospinal fluid (CSF) lymphocytes from patients with multiple sclerosis (MS) were transformed with human T cell leukemia/lymphoma virus (HTLV I and HTLV II) and the resulting cell lines characterized by cell surface phenotyping and functional assessment. The lines were predominantly of the CD4 helper/induce phenotype although the HTLV II lines contained 10-20% CD8+ cells. The lines appeared to be activated cells; the majority were TA1+, HLA-DR+, and TAC+ (CD25+). Interestingly, they were OKT10- (CD38-). Functionally, the lines contained no natural killer (NK) activity and were modestly cytotoxic in the antibody-dependent cellular cytotoxicity (ADCC) assay. They were poor proliferative responders to antigens and mitogens though the HTLV II lines did respond to interleukin 2 (IL2). The HTLV I lines were either nonresponsive to or were suppressed by IL2. Early passages of two of the lines produced IL2 but this was lost as the cells were passed in culture. The cell lines were capable of either directly or indirectly suppressing pokeweed mitogen (PWM)-driven immunoglobulin production by normal B cells. In addition, the lines were capable of producing gamma-interferon (IFN-gamma), lymphotoxin (LT), an interleukin 1 (IL1)-like factor, glial growth promoting factor (GGPF), and IL6. The advantage of these lines over clones or cell lines developed using other techniques is their growth in the absence of feeder layers or IL2 and their ability to be cloned and to grow in culture indefinitely.

Interferon-induced expression of class II major histocompatibility antigens in the major histocompatibility complex (MHC) class II deficiency syndrome.

Class II antigens encoded by genes of the major histocompatibility complex (MHC) are expressed by a variety of cell types and have a vital role in the cellular interactions required for an effective immune response. We have analyzed the regulation of HLA-DR, DP, and DQ class II antigen expression on cells of different lineage from an immunodeficient patient with the MHC class II deficiency syndrome. T and B lymphocytes, monocytes, and fibroblasts, which initially expressed no class II antigens, were treated with inductive stimuli that normally lead to enhanced expression of class II antigens. Monocytes, but not fibroblasts, cultured for 48-96 hr in the presence of recombinant gamma interferon expressed all three types of class II antigens. In contrast, T lymphocytes did not express class II antigens following their exposure to a variety of stimuli, including activation with phytohemagglutinin and culture in the presence of interleukin-2, transformation by the retrovirus HTLV-1 or HTLV-2, or exposure to the demethylating agent 5-azacytidine. Similarly, class II antigens were not induced on B cells by cross-linkage of surface immunoglobulin molecules with anti-mu, exposure to Epstein-Barr virus, or treatment with soluble factors secreted by activated T cells. These results demonstrate that the regulation of class II MHC antigen expression by monocytes and lymphocytes is dissimilar and suggest that different regulatory genes are involved in the control of class II antigen expression by cells of different lineage.

Granulocyte-macrophage colony-stimulating factor enhances neutrophil function in acquired immunodeficiency syndrome patients.

We conducted a clinical trial of human recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) in leukopenic patients with acquired immunodeficiency syndrome (AIDS) and analyzed neutrophil function before, during, and after in vivo administration of rGM-CSF. Prior to GM-CSF infusion, AIDS patients' neutrophil superoxide generation and neutrophil antibody-dependent cell-mediated cytotoxicity were enhanced normally by in vitro exposure to GM-CSF. Neutrophil phagocytosis and intracellular killing of Staphylococcus aureus were also normal in the majority of these patients. Two patients, however, had discrete neutrophil functional defects: one in phagocytosis and one in intracellular killing. During the period of GM-CSF infusion, these abnormalities were corrected. The number of circulating neutrophils increased in all patients treated with GM-CSF in a dose-dependent manner. Neutrophils produced in vivo in response to GM-CSF administration functioned normally and there was evidence for neutrophil priming and activation in vivo. We conclude that GM-CSF treatment of AIDS patients leads to the production of functionally active neutrophils, suggesting therapeutic potential for GM-CSF in the treatment of patients with impaired host defense.

Establishment of eosinophilic sublines from human promyelocytic leukemia (HL-60) cells: demonstration of multipotentiality and single-lineage commitment of HL-60 stem cells.

Recent observations indicating that the HL-60 human acute promyelocytic leukemia cell line contains a minor eosinophil population in addition to neutrophil and mononuclear phagocyte progenitors suggest the multipotentiality of HL-60 stem cells. In order to clarify multilineage differentiation and commitment to single-lineage progenitors we analyzed HL-60 colonies formed in methylcellulose. In an HL-60 parent line with a relatively high eosinophil content (5.5%), 36% of the spontaneous colonies consisted partly or wholly of eosinophilic cells. After two rounds of subcloning in methylcellulose, two eosinophilic sublines and two neutrophilic sublines were established. These lines have been in continuous liquid culture for more than four months, and they show stable single-lineage differentiation. Purified biosynthetic GM-CSF, which stimulates normal CFU-GM and CFU-EO, induced monocytic differentiation but no eosinophilic differentiation in the neutrophilic sublines and no neutrophilic or monocytic differentiation in the eosinophilic sublines. These observations indicate that HL-60 stem cells are multipotent and capable of spontaneous commitment to single-lineage progenitors. The eosinophilic HL-60 sublines should facilitate studies on the production and function of human eosinophils and the single-lineage sublines will allow further analysis of leukemic cell differentiation and stem cell commitment.

The x gene is essential for HTLV replication.

The human T-cell leukemia viruses (HTLV) are associated with T-cell malignancies in man and will transform normal human T cells in vitro. The mechanism of malignant transformation by HTLV is unknown but appears to be distinct from that of other classes of retroviruses, which induce malignant transformation through viral or cellular oncogenes. Recently a new gene, termed x, was identified in HTLV. This gene has been hypothesized to be the transforming gene of HTLV because of its conservation within the HTLV class of retroviruses. By in vitro mutagenesis of the HTLV-II x gene, it is now demonstrated that the presence of a functional x gene product is necessary for efficient HTLV transcription. Therefore, these studies provide direct evidence for an important function of the x gene in HTLV replication. The functional analogies between the x gene and transcriptional regulatory genes of some DNA viruses suggest that these viruses share similar mechanisms for cellular transformation.

Human T-cell leukemia virus type II transforms normal human lymphocytes.

A unique human retrovirus (human T-cell leukemia virus type II, HTLV-II), isolated from a patient with a T-cell variant of hairy-cell leukemia, has been shown to be distinct from the more common isolates of human T-cell leukemia virus. This virus was tested for its ability to transform normal human peripheral blood lymphocytes. The HTLV-II-infected T-cell line Mo-T was lethally x-irradiated and cocultivated with normal human peripheral blood lymphocytes. The cocultivation of normal cells with Mo-T cells resulted in the transformation of the normal cells as evidenced by the establishment of permanent cell lines. The transformed cells are infected with HTLV-II as shown by immunologic tests and molecular hybridization. The cells are of mature T-cell phenotype and constitutively produce lymphokines. An Epstein-Barr virus-transformed lymphoblast B-cell line established from peripheral blood cells of the patient Mo, designated Mo-B, also was found to be infected with HTLV-II. All HTLV-II-infected cells, including the Mo-B cells, were capable of transforming normal cells of T-cell phenotype by transmission of virus by cocultivation. These results indicate that HTLV-II infects both B and T cells but transforms normal human peripheral blood lymphocytes of T-cell phenotype.

Ultrastruct and tartrate-resistant acid phosphatase localization in a T-cell hairy-cell leukemia cell line.

Hairy-cell leukemia is characterized clinically in splenomegaly and pancytopenia and pathologically by the proliferation in hematopoietic tissue of cells containing the tartrate-resistant isozyme 5 of acid phosphatase. We have described a patient with a T-lymphocyte variant of this disease. A permanent cell line obtained from the spleen of this patient has the biological and enzymatic characteristics of the fresh leukemic cells. We have used this line to study the surface morphology, ultrastructure, and ultrastructural localization of acid phosphatase in defined T-lymphoid hairy cells. The surface of the cells of the permanent line was smooth but many hair-like projections appeared after exposure to phytohemagglutinin (PHA). There was little acid phosphatase reaction produce visualized when beta-glycerophosphate was used as a substrate. With sodium haphthol AS-BI phosphoric acid heavy deposits were seen in the perinuclear membrane, mitochondria, and rough endoplasmic reticulum. Exposure to PHA and pokeweed mitogen resulted in increased reaction product, suggesting increased enzyme synthesis. Tartrate-resistant acid phosphatase was localized in the same organelles.

Origin of human bone marrow fibroblasts.

We investigated the origin of bone marrow fibroblasts in three bone marrow transplant recipients with aplastic anaemia and leukaemia who received grafts from HLA-identical siblings of opposite sex. The patients were conditioned for transplantation with high doses of cytotoxic drugs and 300--1000 rads total body irradiation. After transplantation, bone marrow cells were cultured in T flasks for 3 weeks and the adherent cells were then trypsinized and passaged weekly. After several passages the cells had the typical morphology and growth pattern of fibroblasts. Metaphases from these cells were all of recipient sex type. In contrast, haematopoietic cells and lymphocytes obtained at the same time were of donor sex type. Our findings indicate that the human bone marrow fibroblast is not derived from a precursor common to haemotopoietic cells or lymphocytes. The bone marrow fibroblast appears to be a mesenchymal cell, unrelated to haematopoietic stem cells, which is capable of in vitro proliferation after as much as 1000 rads of total body irradiation.

Production of erythroid-potentiating activity by a human T-lymphoblast cell line.

We derived a human T-lymphoblast cell line (Mo) that constitutively elaborates certain lymphokines. The Mo cells produce a colony-stimulating factor necessary for the growth of human granulocyte-monocyte precursors in vitro as well as an erythroid-potentiating activity (EPA) that enhances the proliferation of human erythroid progenitors in vitro. In the presence of serum, the EPA in Mo-conditioned medium stimulated the growth of small and large erythroid colonies almost 2-fold. EPA was also produced in serum-free medium, and, when assayed in serum-free cultures of human erythroid progenitors, it stimulated colony growth about 3-fold. The EPA produced by the Mo cell line did not stimulate normal murine erythroid progenitors (CFU-E) or Friend erythroleukemia cell growth in vitro. EPA was inactivated by protease treatment but was remarkably heat stable, with most of the activity recovered after boiling for 15 min. Preliminary biochemical characterization suggests that EPA is an acidic glycoprotein with molecular weight approximately 45,000. EPA is clearly separable from colony-stimulating factor on the basis of heat stability and gel-filtration chromatography. The present observations provide strong support for the concept that activated T cells produce humoral factors important in the regulation of erythropoiesis. The availability of a cell line producing human EPA should facilitate the characterization of the protein and permit definitive studies of its biologic effects.

Trimethoprim and sulphamethoxazole inhibition of haematopoiesis in vitro.

The effect of trimethoprim and sulphamethoxazole on haematopoiesis was studied in vitro using cloning techniques for human and murine erythroid and granulocytic precursor cells. Trimethoprim was found to inhibit granulopoiesis and erythropoiesis in vitro in a dose-dependent fashion with approximately 50% inhibition of human erythroid and granulocytic colonies at a therapeutically achievable concentration of 7 micrograms/ml. Sulphamethoxazole was also shown to impair haematopoiesis in vitro. The inhibition caused by both these constituents of co-trimoxazole was completely reversed by folinic acid. The data suggest that co-trimoxazole can impair human haematopoiesis by inhibition of tetrahydrofolate synthesis. These observations suggest that the clinical haematopoietic toxicity of trimethoprim-sulphamethoxazole can be abrogated by simultaneous administration of folinic acid.

Human T lymphocyte cell line producing colony-stimulating activity.

We derived a permanent human T lymphocyte cell line that elaborates a potent colony-stimulating activity (CSA). The line was established with spleen cells from a patient with a T lymphocyte variant of hairy-cell leukemia. These cells form rosettes with sheep erythrocytes, show a proliferative response to phytohemagglutinin, and are lysed by antithymocyte globulin. They do not synthesize immunoglobulin, nor do they contain Epstein-Barr virus. CSA is regularly detected in the supernatant medium after 3 days culture. In the presence of PHA there is augmented elaboration of CSA; maximal activity is reached by 2 days and is 20% greater than that produced by a feeder layer of 1 X 10(6) peripheral blood leukocytes. One microliter of the supernatant material stimulated colony formation from the light-density nonadherent fraction of human bone marrow; there was maximal activity between 10 and 50 microliter/ml. Conditioned medium from these cells has little effect in stimulating CFU-C from murine bone marrow. The availability of a human T lymphocyte line producing CSA will provide a source for large quantities of the lymphocyte-derived hormone and permit a definition of factors modulating the interaction of T lymphocytes with granulocyte and monocyte stem cells.