Decreased signalling of EphA4 improves functional performance and motor neuron survival in the SOD1G93A ALS mouse model

Amyotrophic lateral sclerosis (ALS) is an untreatable, progressive, neurodegenerative disease specifically affecting motor neurons. Recently, the tyrosine kinase receptor EphA4 was directly implicated in ALS disease progression. We report that a long-lived mutated form of the EphA4 antagonist EphA4-Fc (mutEphA4-Fc), which blocks EphA4 binding to its ligands and inhibits its function, significantly improved functional performance in SOD1G93A ALS model mice, as assessed by rotarod and hind-limb grip strength tests. Further, heterozygous motor neuron-specific EphA4 gene deletion in SOD1G93A mice promoted significant improvement in functional performance during the disease course and a delay in disease onset relative to control mice. Importantly, mice in the heterozygous deletion group showed significantly improved survival of motor neurons and architecture of endplates of neuromuscular junctions compared with control and homozygous EphA4-deletion groups. Our novel results show that EphA4 signalling directly regulates motor neuron survival and that mutEphA4-Fc is a promising therapeutic candidate to slow disease progression in ALS.

Patient-derived glioblastoma cells show significant heterogeneity in treatment responses to the inhibitor-of-apoptosis-protein antagonist birinapant

Background:

Resistance to temozolomide (TMZ) greatly limits chemotherapeutic effectiveness in glioblastoma (GBM). Here we analysed the ability of the Inhibitor-of-apoptosis-protein (IAP) antagonist birinapant to enhance treatment responses to TMZ in both commercially available and patient-derived GBM cells.

Methods:

Responses to TMZ and birinapant were analysed in a panel of commercial and patient-derived GBM cell lines using colorimetric viability assays, flow cytometry, morphological analysis and protein expression profiling of pro- and antiapoptotic proteins. Responses in vivo were analysed in an orthotopic xenograft GBM model.

Results:

Single-agent treatment experiments categorised GBM cells into TMZ-sensitive cells, birinapant-sensitive cells, and cells that were insensitive to either treatment. Combination treatment allowed sensitisation to therapy in only a subset of resistant GBM cells. Cell death analysis identified three principal response patterns: Type A cells that readily activated caspase-8 and cell death in response to TMZ while addition of birinapant further sensitised the cells to TMZ-induced cell death; Type B cells that readily activated caspase-8 and cell death in response to birinapant but did not show further sensitisation with TMZ; and Type C cells that showed no significant cell death or moderately enhanced cell death in the combined treatment paradigm. Furthermore, in vivo, a Type C patient-derived cell line that was TMZ-insensitive in vitro and showed a strong sensitivity to TMZ and TMZ plus birinapant treatments.

Conclusions:

Our results demonstrate remarkable differences in responses of patient-derived GBM cells to birinapant single and combination treatments, and suggest that therapeutic responses in vivo may be greatly affected by the tumour microenvironment.

The Effect of Cytokines on the Expression of Mhc Antigens and Icam-1 by Normal and Transformed Synoviocytes

We report the expression on synovial cells of cell surface molecules known to be involved in T cell activation by antigen presenting cells. Normal human synovial fibroblasts and a human synovial cell line transformed with the SV40 large T antigen were used for in vitro stimulation studies with recombinant cytokines. We demonstrate an increase in MHC-A, B, C expression in normal synovial cells in response to recombinant interferon gamma (r gamma IFN), tumour necrosis factor alpha and beta (rTNF alpha and beta) and interleukin-1 (rIL-1 alpha). Intercellular adhesion molecular-1 (ICAM-1) expression was increased in parallel with MHC Class I. The combination of r gamma IFN and rTNF alpha was additive in its effect on ICAM-1 expression. Northern blot analysis suggests that ICAM-1 expression in synovial cells is controlled at the level of transcription. In contrast, MHC Class II (HLA-DR) was only significantly induced by r gamma IFN. Other stimuli including interleukin-4 (IL-4), interleukin 6 (IL-6), granulocyte macrophage colony stimulating factor (GM-CSF) and prostaglandin E2 (PGE2) did not affect the expression of ICAM-1 or MHC Class I and II. Leucocyte function antigen 3 (LFA-3) expression was not affected by any of the stimuli tested. Immunoperoxidase staining of rheumatoid synovial tissue confirmed enhanced in vivo expression of ICAM-1 in rheumatoid arthritis. These changes are discussed in the context of T cell activation in inflammatory arthritis.

Epigenetic silencing of EphA1 expression in colorectal cancer is correlated with poor survival

Aberrant expression of Eph and ephrin proteins has well-established functions in oncogenesis and tumour progression. We describe EphA1 expression in 6 colorectal cancer (CRC) cell lines, 18 controls and 125 CRC specimens. In addition, a well-characterised cohort of 53 paired normal colon and CRCs was also assessed. Expression of EphA1 mRNA was assessed by quantitative real-time PCR and correlated with protein expression by flow cytometry, immunoprecipitation, western blotting and immunohistochemistry. Significant upregulation (2- to 10-fold) of EphA1 was seen in over 50% of cases (P=0.005) whereas many of the remainder showed downregulation of EphA1. Intriguingly, EphA1 over-expression was more prevalent in stage II compared to stage III CRCs (P=0.02). Low EphA1 expression significantly correlated with poor survival (P=0.02). Epigenetic silencing appeared to explain the loss of EphA1 expression as methylation of the EphA1 CpG island strongly correlated with low EphA1 expression (P<0.01). Furthermore, EphA1 re-expression could be induced by treatment with demethylating agents. Our findings identify EphA1 as a potential prognostic marker in CRC. Although therapies targeting high EphA1 expression seem plausible in CRC, the loss of expression in advanced disease suggests a potential risk that targeted therapy, by selecting for loss of expression, might contribute to disease progression.

Hypermethylation of the 5' CpG island of the gene encoding the serine protease Testisin promotes its loss in testicular tumorigenesis

The Testisin gene (PRSS21) encodes a glycosylphosphatidylinositol (GPI)-linked serine protease that exhibits testis tissue-specific expression. Loss of Testisin has been implicated in testicular tumorigenesis, but its role in testis biology and tumorigenesis is not known. Here we have investigated the role of CpG methylation in Testisin gene inactivation and tested the hypothesis that Testisin may act as a tumour suppressor for testicular tumorigenesis. Using sequence analysis of bisulphite-treated genomic DNA, we find a strong relationship between hypermethylation of a 385 bp 5′ CpG rich island of the Testisin gene, and silencing of the Testisin gene in a range of human tumour cell lines and in 100% (eight/eight) of testicular germ cell tumours. We show that treatment of Testisin-negative cell lines with demethylating agents and/or a histone deacetylase inhibitor results in reactivation of Testisin gene expression, implicating hypermethylation in Testisin gene silencing. Stable expression of Testisin in the Testisin-negative Tera-2 testicular cancer line suppressed tumorigenicity as revealed by inhibition of both anchorage-dependent cell growth and tumour formation in an SCID mouse model of testicular tumorigenesis. Together, these data show that loss of Testisin is caused, at least in part, by DNA hypermethylation and histone deacetylation, and suggest a tumour suppressor role for Testisin in testicular tumorigenesis.

Signals from Eph and ephrin proteins: a developmental tool kit

Interactions between Eph receptors and their ligands the ephrin proteins are critically important in many key developmental processes. Emerging evidence also supports a role for these molecules in postembryonic tissues, particularly in pathological processes, including tissue injury and tumor metastasis. We review the signaling mechanisms that allow the 14 Eph and nine ephrin proteins to deliver intracellular signals that regulate cell shape and movement. What emerges is that the initiation of these signals is critically dependent on which Eph and ephrin proteins are expressed, the level of their expression, and, in some cases, which splice variants are expressed. Diversity at the level of initial interaction and in the downstream signaling processes regulated by Eph-ephrin signaling provides a subtle, versatile system of regulation of intercellular adhesion, cell shape, and cell motility.

Characterization of a human synovial cell antigen: VCAM-1 and inflammatory arthritis

The contribution of synovial cells to the pathogenesis of rheumatoid arthritis (RA) is only partly understood. Monoclonal antibody (mAb) 1D5 is one of very few mAb ever raised against RA synovial cells in order to study the biology of these cells. Studies on the expression pattern and structural features of the 1D5 Ag suggest that 1D5 recognizes human vascular cell adhesion molecule-1 (VCAM-1), which is an intercellular adhesion molecule. Vascular cell adhesion molecule-1 may be involved in a number of crucial intercellular interactions in RA.

Functional heterogeneity within rhodamine123(lo) Hoechst33342(lo/sp) primitive hemopoietic stem cells revealed by pyronin Y

OBJECTIVE

The aim of this study was to determine the function of primitive hematopoietic stem cells (PHSC) at phases G(0) and G(1) of the cell cycle.

MATERIALS AND METHODS

A combination of supravital dyes rhodamine123 (Rh), Hoechst33342 (Ho), and pyronin (PY) was used to isolate the G(0) and G(1) subsets of PHSC. A competitive repopulation assay was used to evaluate their in vivo function.

RESULTS

We confirmed that the Rh(lo)Lin(-)Kit(+)Sca-1(+) PHSC were relatively quiescent when compared with the more mature Rh(hi)Lin(-)Kit(+)Sca-1(+) HSC and Rh(hi)Lin(-)Kit(+)Sca-1(-) progenitors. In addition, cells with Rh(lo)Lin(-)Kit(+)Sca-1(+), Rh(lo)Ho(lo)Lin(-)Sca-1(+), or Rh(lo)Ho(sp)Lin(-)Sca-1(+) phenotypes identified the same cell population. We further subfractionated the Rh(lo)Ho(lo/sp)Lin(-)Sca-1(+) PHSC using PY into PY(lo) and PY(hi) subsets. Limiting dilution analysis revealed that the frequency of long-term in vivo competitive repopulating units (CRU) of the PY(lo)Rh(lo)Ho(lo/sp) PHSC was 1 in 10 cells, whereas there was at least a three-fold lower frequency in those isolated at the G(1) phase (PY(hi)). We found a dose-dependent PY-mediated cytotoxicity that at moderate concentration affected most of the murine hematopoietic compartment but spared the early HSC compartment.

CONCLUSION

Our data confirm that the HSC compartment is hierarchically ordered on the basis of quiescence and further extend this concept to PY-mediated cytotoxicity. PY supravital dye can be used to reveal functional heterogeneity within the Rh(lo)Ho(lo/sp) PHSC population but is of limited use in dissecting the relatively more mature hematopoietic stem/progenitor cell population.

Development and reorganization of corticospinal projections in EphA4 deficient mice

The Eph family of receptor tyrosine kinases and their ligands, the ephrins, are important regulators of axon guidance and cell migration in the developing nervous system. Inactivation of the EphA4 gene results in axon guidance defects of the corticospinal tract, a major descending motor pathway that originates in the cortex and terminates at all levels of the spinal cord. In this investigation, we report that although the initial development of the corticospinal projection is normal through the cortex, internal capsule, cerebral peduncle, and medulla in the brain of EphA4 deficient animals, corticospinal axons exhibit gross abnormalities when they enter the gray matter of the spinal cord. Notably, many corticospinal axons fail to remain confined to one side of the spinal cord during development and instead, aberrantly project across the midline, terminating ipsilateral to their cells of origin. Given the possible repulsive interactions between EphA4 and one of its ligands, ephrinB3, this defect could be consistent with a loss of responsiveness by corticospinal axons to ephrinB3 that is expressed at the spinal cord midline. Furthermore, we show that EphA4 deficient animals exhibit ventral displacement of the mature corticospinal termination pattern, suggesting that developing corticospinal axons, which may also express ephrinB3, fail to be repelled from areas of high EphA4 expression in the intermediate zone of the normal spinal cord. Taken together, these results suggest that the dual expression of EphA4 on corticospinal axons and also within the surrounding gray matter is very important for the correct development and termination of the corticospinal projection within the spinal cord.

Characterization of the Epha1 receptor tyrosine kinase: expression in epithelial tissues

The Eph family of receptor tyrosine kinases plays a crucial role during development and is implicated in oncogenesis. Using a partial cDNA clone of an Eph-related kinase (Esk) we isolated the complete coding region of a gene which we show to be murine EphA1 by both structural and functional criteria. The chromosomal localization is shown to be syntenic to hEphA1 and the genomic organization also shows distinct features found in the hEphA1 gene. Functionally, in keeping with findings for the human homologue, both soluble recombinant and "native" mEphA1 show preferential binding to ephrin A1. However, we also observed significant binding to other A-type ligands as has been observed for other Eph receptors. We analysed the expression of mEphA1 mRNA by in situ hybridization on tissue sections. mEphA1 was expressed in epithelial elements of skin, adult thymus, kidney and adrenal cortex. Taken together with previous Northern blotting data these results suggest that mEphA1 is expressed widely in differentiated epithelial cells.

Kinase-dependent and kinase-independent functions of EphA4 receptors in major axon tract formation in vivo

The EphA4 receptor tyrosine kinase regulates the formation of the corticospinal tract (CST), a pathway controlling voluntary movements, and of the anterior commissure (AC), connecting the neocortical temporal lobes. To study EphA4 kinase signaling in these processes, we generated mice expressing mutant EphA4 receptors either lacking kinase activity or with severely downregulated kinase activity. We demonstrate that EphA4 is required for CST formation as a receptor for which it requires an active kinase domain. In contrast, the formation of the AC is rescued by kinase-dead EphA4, suggesting that in this structure EphA4 acts as a ligand for which its kinase activity is not required. Unexpectedly, the cytoplasmic sterile-alpha motif (SAM) domain is not required for EphA4 functions. Our findings establish both kinase-dependent and kinase-independent functions of EphA4 in the formation of major axon tracts.

Expression of the Wilms' tumor suppressor gene, WT1, reduces the tumorigenicity of the leukemic cell line M1 in C.B-17 scid/scid mice

The Wilms' tumor suppressor gene, WT1, encodes a transcription of the Cys2-His2 zinc finger type. Loss of WT1 gene function has been implicated in the development of malignancies including Wilms' tumor and acute leukemias. We have shown previously that ectopic expression of WT1 +KTS isoforms in murine M1 leukemic cells spontaneously induces monocytic differentiation without the requirement for external differentiation-inducing stimuli. To determine whether these observed effects in vitro corresponded to a reduction in tumorigenicity in vivo, parental M1, control M1.Neo, and M1.WT1 +KTS cells were transplanted into C.B-17 scid/scid mice, and the growth and metastatic behavior of the cell lines were monitored for a period of 20 weeks. Mice inoculated either s.c. on the flank or directly into the peritoneal cavity, with M1 cells stably expressing WT1 +KTS isoforms exhibited a marked decrease in tumor formation compared with control groups. Moreover, tumors arising in mice after the injection of M1.WT1 +KTS cells exhibited a loss in ectopic WT1 protein expression. Confirmation that the tumors arose from M1.WT1 +KTS cells was achieved by the amplification of the introduced transgene from tumor samples and indicates that the tumorigenicity of leukemic M1 cells in these animals correlates with a loss in WT1 expression. This investigation is the first to demonstrate the tumor-suppressive effects of WT1 expression in a leukemic cell line, further advancing the notion that WT1 acts as a differentiation-promoting gene during hematopoiesis and that loss of functional WT1 expression may contribute to leukemogenesis in vivo.

A phase I and pharmacokinetic study of subcutaneously-administered recombinant human interleukin-4 (rhuIL-4) in patients with advanced cancer

PURPOSE

To investigate the pharmacokinetics and tolerability of recombinant human interleukin-4 (rhuIL-4), administered by daily subcutaneous injection, in patients with advanced cancer.

PATIENTS AND METHODS

Fourteen patients with advanced cancer treated with rhuIL-4 at escalating dose levels of 0.25, 1.0 and 5.0 microg/kg/day, on days 1, 8-17, and 28-57. The primary endpoints of the study were toxicity of rhuIL-4 and the determination of the pharmacokinetics of rhuIL-4 when given by subcutaneous injection. Secondary endpoints included effects on blood counts, hematopoietic cell precursors, and various immunologic parameters.

RESULTS

rhuIL-4 was well tolerated at all three dose levels. Detectable serum levels of IL-4 were found in patients at the 1.0 and 5.0 microg/kg/day dose levels. Peak serum IL-4 levels were achieved about 2 h after injection and IL-4 was still detectable 8 h after injection. No grade 4 toxicities were observed and grade 3 toxicities were confined to fever, headache and raised hepatic alkaline phosphatase. No consistent hematological or immunologic effects were observed. Although therapeutic efficacy was not an endpoint, one complete response (Hodgkin's disease) was observed. One patient with chronic lymphocytic leukemia progressed on therapy.

CONCLUSION

rhuIL-4 up to 5.0 microg/kg/day is well tolerated when given by subcutaneous injection. Biologically relevant serum IL-4 levels can be achieved and sustained for at least 8 h after a single injection.

Cloning and characterization of EphA3 (Hek) gene promoter: DNA methylation regulates expression in hematopoietic tumor cells

The Eph family of receptor tyrosine kinases (RTK) has restricted temporal and spatial expression patterns during development, and several members are also found to be upregulated in tumors. Very little is known of the promoter elements or regulatory factors required for expression of Eph RTK genes. In this report we describe the identification and characterization of the EphA3 gene promoter region. A region of 86 bp located at -348 bp to -262 bp upstream from the transcription start site was identified as the basal promoter. This region was shown to be active in both EphA3-expressing and -nonexpressing cell lines, contrasting with the widely different levels of EphA3 expression. We noted a region rich in CpG dinucleotides downstream of the basal promoter. Using Southern blot analyses with methylation-sensitive restriction enzymes and bisulfite sequencing of genomic DNA, sites of DNA methylation were identified in hematopoietic cell lines which correlated with their levels of EphA3 gene expression. We showed that EphA3 was not methylated in normal tissues but that a subset of clinical samples from leukemia patients showed extensive methylation, similar to that observed in cell lines. These results suggest that DNA methylation may be an important mechanism regulating EphA3 transcription in hematopoietic tumors.

An early developmental role for eph-ephrin interaction during vertebrate gastrulation

Eph receptor tyrosine kinases (RTK) and their ephrin ligands are involved in the transmission of signals which regulate cytoskeletal organisation and cell migration, and are expressed in spatially restricted patterns at discrete phases during embryogenesis. Loss of function mutants of Eph RTK or ephrin genes result in defects in neuronal pathfinding or cell migration. In this report we show that soluble forms of human EphA3 and ephrin-A5, acting as dominant negative inhibitors, interfere with early events in zebrafish embryogenesis. Exogenous expression of both proteins results in dose-dependent defects in somite development and organisation of the midbrain-hindbrain boundary and hindbrain. The nature of the defects as well as the distribution and timing of expression of endogenous ligands/receptors for both proteins suggest that Eph-ephrin interaction is required for the organisation of embryonic structures by coordinating the cellular movements of convergence during gastrulation.

EphA4 (Sek1) receptor tyrosine kinase is required for the development of the corticospinal tract

Members of the Eph family of tyrosine kinase receptors have been implicated in the regulation of developmental processes and, in particular, axon guidance in the developing nervous system. The function of the EphA4 (Sek1) receptor was explored through creation of a null mutant mouse. Mice with a null mutation in the EphA4 gene are viable and fertile but have a gross motor dysfunction, which is evidenced by a loss of coordination of limb movement and a resultant hopping, kangaroo-like gait. Consistent with the observed phenotype, anatomical studies and anterograde tracing experiments reveal major disruptions of the corticospinal tract within the medulla and spinal cord in the null mutant animals. These results demonstrate a critical role for EphA4 in establishing the corticospinal projection.

Distinct subdomains of the EphA3 receptor mediate ligand binding and receptor dimerization

Eph receptor tyrosine kinases and their ligands (ephrins) are highly conserved protein families implicated in patterning events during development, particularly in the nervous system. In a number of functional studies, strict conservation of structure and function across distantly related vertebrate species has been confirmed. In this study we make use of the observation that soluble human EphA3 (HEK) exerts a dominant negative effect on somite formation and axial organization during zebrafish embryogenesis to probe receptor function. Based on exon structure we have dissected the extracellular region of EphA3 receptor into evolutionarily conserved subdomains and used kinetic BIAcore analysis, mRNA injection into zebrafish embryos, and receptor transphosphorylation analysis to study their function. We show that ligand binding is restricted to the N-terminal region encoded by exon III, and we identify an independent, C-terminal receptor-dimerization domain. Recombinant proteins encoding either region in isolation can function as receptor antagonists in zebrafish. We propose a two-step mechanism of Eph receptor activation with distinct ligand binding and ligand-independent receptor-receptor oligomerization events.

Expression of the Wilms' tumor suppressor gene, WT1, is upregulated by leukemia inhibitory factor and induces monocytic differentiation in M1 leukemic cells

The Wilms' tumor gene, WT1, encodes a transcription factor of the Cys2-His2 zinc finger type. The functional significance of WT1 expression in leukemias, in addition to tissues and cell lines of hematopoietic origin, has not been determined. Using the murine myeloblastic leukemia cell line M1 as a model for macrophage differentiation, expression of WT1 is shown to be activated in M1 cells 24 hours after differentiation induction by leukemia inhibitory factor (LIF). Upregulation of WT1 in these cells is associated with cellular differentiation, coinciding with expression of the monocyte/macrophage marker c-fms, and the appearance of mature cells. WT1 isoforms lacking the KTS insert are unable to be ectopically expressed in M1 cells. Stable expression of the WT1 isoforms containing the KTS insert leads to spontaneous differentiation of the M1 myeloblasts through the monocytic differentiation pathway. These cells express c-fms, in addition to the myeloid-specific cell surface marker Mac-1. Exposure of these cells to LIF results in the rapid onset of terminal macrophage differentiation, accompanied by apoptotic cell death. These results show that the WT1 gene is an important regulator of M1 cell monocytic differentiation in vitro, and suggests a potential role for this gene in the molecular control of hematopoiesis.

Ligand for EPH-related kinase (LERK) 7 is the preferred high affinity ligand for the HEK receptor

HEK is a member of the EPH-like receptor tyrosine kinase family, which appear to have roles in development and oncogenesis. Recently, we purified a soluble HEK ligand which is also a ligand (AL1) for the HEK-related receptor EHK1. Promiscuity appears to be a characteristic feature of interactions between the EPH-like receptors and their ligands, termed ligands for EPH-related kinases (LERKs). This prompted us to analyze the interactions between the HEK exodomain and fusion proteins comprising candidate LERKs and the Fc portion of human IgG1 (Fc) or a FLAGTM-peptide tag by surface plasmon resonance, size exclusion high performance liquid chromatography, sedimentation equilibrium, and transphosphorylation. Our results indicate that AL1/LERK7 is the preferred high-affinity ligand for HEK, forming a stable 1:1 complex with a dissociation constant of 12 nM. As expected the apparent affinities of bivalent fusion proteins of LERKs and the Fc portion of human IgG1 had significantly reduced dissociation rates compared with their monovalent, FLAGTM-tagged derivatives. High-avidity binding of monovalent ligands can be achieved by antibody-mediated cross-linking of monovalent ligands and with LERK7 results in specific phosphorylation of the receptor. By extrapolation, our findings indicate that some of the reported LERK-receptor interactions are a consequence of the use of bivalent ligand or receptor constructs and may be functionally irrelevant.

G-CSF-mobilized peripheral blood progenitor cells: in vitro growth pattern and hematopoietic growth factor receptor profile

The kinetics of colony formation by granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood progenitor cells (PBPCs) were monitored using clone-mapping experiments. Compared with normal resting bone marrow (BM), where the ratio of Day 7:Day 14 granulocyte-macrophage colony-forming cells (GM-CFCs) was 1:0.76-1.9, PB was found to be relatively deficient in progenitor cells with the capacity to form colonies by Day 7 (median ratio Day 7:Day 14 1:21). The most mature Day 7 GM-CFCs, those dispersing or extinguishing before Day 14, were almost absent in PB (< 1% of all GM-CFCs) but comprised 77% of Day 7 GM-CFCs and 32% of all GM-CFCs in BM. The expression patterns of high affinity receptors for G-CSF, GM-CSF, stem cell factor (SCF), and the ligand for flk-2 on CD38hi and CD38-/dim PB CD34+ cells were determined by binding of 125I-labeled ligand and autoradiography. G-CSF receptor (G-CSFR) expression was detected on approximately 25% of CD38-/dim cells (estimated mean 105 receptors per positive cell) and was higher in CD38hi cells (approximately 50% positive, with a mean of 227 receptors per cell). GM-CSFR expression was low (approximately 25% of cells positive, mean of 120 receptor per cell) and did not vary with CD38 expression. c-kit (SCFR) and flk-2 were expressed by > or = 90% and > or = 80% of CD34+ cells, respectively. SCF binding per cell was greater in the CD38hi population, while flk-2 expression did not vary with CD38 expression. These results confirm the heterogeneity of receptor expression by progenitor cells and imply differential regulation of receptor expression during maturation.

Purification of a ligand for the EPH-like receptor HEK using a biosensor-based affinity detection approach

Advances in screening technologies allowing the identification of growth factor receptors solely by virtue of DNA or protein sequence comparison call for novel methods to isolate corresponding ligand growth factors. The EPH-like receptor tyrosine kinase (RTK) HEK (human EPH-like kinase) was identified previously as a membrane antigen on the LK63 human pre-B-cell line and overexpression in leukemic specimens and cell lines suggested a role in oncogenesis. We developed a biosensor-based approach using the immobilized HEK receptor exodomain to detect and monitor purification of the HEK ligand. A protein purification protocol, which included HEK affinity chromatography, achieved a 1.8 X 10(6)-fold purification of an approximately 23-kDa protein from human placental conditioned medium. Analysis of specific sHEK (soluble extracellular domain of HEK) ligand interactions in the first and final purification steps suggested a ligand concentration of 40 pM in the source material and a Kd of 2-3 nM. Since the purified ligand was N-terminally blocked, we generated tryptic peptides and N-terminal amino acid sequence analysis of 7 tryptic fragments of the S-pyridylethylated protein unequivocally matched the sequence for AL-1, a recently reported ligand for the related EPH-like RTK REK7 (Winslow, J.W., Moran, P., Valverde, J., Shih, A., Yuan, J.Q., Wong, S.C., Tsai, S.P., Goddard, A., Henzel, W.J., Hefti, F., Beck, K.D., & Caras, I.W. (1995) Neuron 14, 973-981). Our findings demonstrate the application of biosensor technology in ligand purification and show that AL-1, as has been found for other ligands of the EPH-like RTK family, binds more than one receptor.

Embryonic stem cells express multiple Eph-subfamily receptor tyrosine kinases

Eph and its homologues form the largest subfamily of receptor tyrosine kinases. Normal expression patterns of this subfamily indicate roles in differentiation and development, whereas their overexpression has been linked to oncogenesis. This study investigated the potential role of Eph-related molecules during very early embryonic development by examining their expression in embryonic stem (ES) cells and embryoid bodies differentiated from ES cells in vitro. By use of a strategy based on reverse transcriptase-mediated PCR, nine clones containing Eph-subfamily sequence were isolated from ES cells. Of these, eight were almost identical to one of four previously identified molecules (Sek, Nuk, Eck, and Mek4). However, one clone contained sequence from a novel Eph-subfamily member, which was termed embryonic stem-cell kinase or Esk. Northern analysis showed expression of Esk in ES cells, embryoid bodies, day 12 mouse embryos, and some tissues of the adult animal. Levels of expression were similar in ES cells and embryoid bodies. By comparison, Mek4 showed no significant transcription in the ES cell cultures by Northern analysis, whereas Eck displayed stronger signals in ES cells than in the embryoid bodies. These results suggest that Eph-subfamily molecules may play roles during the earliest phases of embryogenesis. Furthermore, the relative importance of different members of this subfamily appears to change as development proceeds.

Tissue factor expression in human leukemic cells

Patients with acute leukemia are at increased risk for thrombotic and hemorrhagic complications, particularly those patients with acute promyelocytic leukemia (APL) undergoing induction chemotherapy. These serious complications have been attributed by some authors to the release of tissue factor (TF) procoagulant activity (PCA), particularly during cytotoxic chemotherapy. In previous studies of normal peripheral blood cells, only cells of the monocyte lineage have been found to express TF PCA. Therefore, several questions remain regarding the origin and characterization of the PCA in malignant leukemic cells, particularly those thought to be derived from granulocyte progenitor cells. We utilized a full-length cDNA probe, several monoclonal antibodies (MAbs) and a sensitive one-stage PCA assay to study the expression of TF in the human cell line, HL-60, in human peripheral blood monocytes/macrophages (Mo/Mø) and in highly purified populations of human polymorphonuclear leukocytes (PMN). In the HL-60 cells we detected low but significant levels of TF mRNA and TF antigen (TF:Ag). In unstimulated cells, coordinate increased levels of TF mRNA, TF:Ag and TF PCA expression were noted following phorbol-ester-induced macrophage differentiation of the cells, but a decreased level of TF mRNA with no change in the basal level of TF:Ag expression occurred following retinoic acid-induced granulocyte differentiation of this cell line. Long-term cultures of stimulated mature Mo/Mø demonstrated initial coordinate expression of TF mRNA, TF:Ag and TF PCA, but TF:Ag expression persisted even after 7 days (when TF PCA was undetectable). No TF PCA, TF:Ag or TF mRNA was demonstrated in highly purified populations of human PMN, regardless of culture conditions. Discordant expression of TF mRNA, TF:Ag and TF PCA in HL-60 cells suggests the possibility of novel, post-synthetic mechanisms for the regulation of TF PCA expression, which might be dependent on the phenotypic differentiation level of the cell. Such mechanisms (yet to be defined) might account for the ability of some leukemic cells, which frequently express characteristics of more than one cell line (e.g. monocytes and granulocytes), to express a TF gene product capable of activating blood coagulation.

A common epitope on platelet integrin alpha IIb beta 3 (glycoprotein IIbIIIa; CD41b/CD61) and alpha M beta 2 (Mac-1; CDIIb/CD18) detected by a monoclonal antibody

Evidence is presented that the mAb 25E11, directed against the platelet integrin alpha IIb beta 3 (glycoprotein IIbIIIa;CD41b/CD61) also binds the distinct myeloid cell integrin alpha M beta 2 (Mac-1;CDIIb/CD18). The Ab is shown to identify only the alpha IIb beta 3 integrin complex and not the individual subunits in crossed Ab immunoelectrophoresis of platelet lysate. From cultured human macrophages, sequential immunoprecipitation of labeled glycoproteins indicated that 25E11 also bound the Mac-1 (CD11b/CD18) complex. This was confirmed using COS-7 and WOP cells doubly transfected with alpha M (CD11b) and beta 2 (CD18) or with alpha L (CD11a) and beta 2 when it was found that the Ab bound only the alpha M beta 2 transfectants. Studies with these cells and the RC2A myeloid cell line stimulated with tetradecanoyl phorbol acetate or FMLP indicated that the 25E11 epitope on Mac-1 did not depend on cell activation for its expression. The rationale for this cross-reactivity is not known, but since the 25E11 Ab inhibits the function of both platelets and myeloid cells, it is likely that this shared epitope is important to integrin function. Given the expression of this epitope on IIbIIIa and Mac-1, the dominant integrins of platelets and granulocyte/macrophage cells, but not on other integrins, a role of this epitope in the early events of inflammation is suggested.

A common epitope on platelet integrin alpha IIb beta 3 (glycoprotein IIbIIIa; CD41b/CD61) and alpha M beta 2 (Mac-1; CDIIb/CD18) detected by a monoclonal antibody

Evidence is presented that the mAb 25E11, directed against the platelet integrin alpha IIb beta 3 (glycoprotein IIbIIIa;CD41b/CD61) also binds the distinct myeloid cell integrin alpha M beta 2 (Mac-1;CDIIb/CD18). The Ab is shown to identify only the alpha IIb beta 3 integrin complex and not the individual subunits in crossed Ab immunoelectrophoresis of platelet lysate. From cultured human macrophages, sequential immunoprecipitation of labeled glycoproteins indicated that 25E11 also bound the Mac-1 (CD11b/CD18) complex. This was confirmed using COS-7 and WOP cells doubly transfected with alpha M (CD11b) and beta 2 (CD18) or with alpha L (CD11a) and beta 2 when it was found that the Ab bound only the alpha M beta 2 transfectants. Studies with these cells and the RC2A myeloid cell line stimulated with tetradecanoyl phorbol acetate or FMLP indicated that the 25E11 epitope on Mac-1 did not depend on cell activation for its expression. The rationale for this cross-reactivity is not known, but since the 25E11 Ab inhibits the function of both platelets and myeloid cells, it is likely that this shared epitope is important to integrin function. Given the expression of this epitope on IIbIIIa and Mac-1, the dominant integrins of platelets and granulocyte/macrophage cells, but not on other integrins, a role of this epitope in the early events of inflammation is suggested.

Optimizing dose and scheduling of filgrastim (granulocyte colony-stimulating factor) for mobilization and collection of peripheral blood progenitor cells in normal volunteers

To define an optimal regimen for mobilizing and collecting peripheral blood progenitor cells (PBPC) for use in allogeneic transplantation, we evaluated the kinetics of mobilization by filgrastim (recombinant met-human granulocyte colony-stimulating factor [r-metHuG-CSF]) in normal volunteers. Filgrastim was injected subcutaneously for up to 10 days at a dose of 3 (n = 10), 5 (n = 5), or 10 micrograms/kg/d (n = 15). A subset of volunteers from each dose cohort underwent a 7L leukapheresis on study day 6 (after 5 days of filgrastim). Granulocyte-macrophage colony-forming cell (GM-CFC) numbers in the blood were maximal after 5 days of filgrastim; a broader peak was evident for CD34+ cells between days 4 and 6. The 95% confidence intervals (CI) for mean number of PBPC per milliliter of blood in the three dose cohorts overlapped on each study day. However, on the peak day, CD34+ cells were significantly higher in the 10 micrograms/kg/d cohort than in a pool of the 3 and 5 micrograms/kg/d cohorts. Mobilization was not significantly influenced by volunteer age or sex. Leukapheresis products obtained at the 10 micrograms/kg/d dose level contained a median GM-CFC number of 93 x 10(4)/kg (range, 50 x 10(4)/kg to 172 x 10(4)/kg). Collections from volunteers receiving lower doses of filgrastim contained a median GM-CFC number of 36 x 10(4)/kg (range, 5 x 10(4)/kg to 204 x 10(4)/kg). The measurement of CD34+ cells per milliliter of blood on the day of leukapheresis predicted the total yield of PBPC in the leukapheresis product (r = .87, P < .0001). Assuming a minimum GM-CFC requirement of 50 x 10(4)/kg (based on our experience with autologous PBPC transplantation), all seven leukapheresis products obtained at the 10 micrograms/kg/d dose level were potentially sufficient for allogeneic transplantation purposes. We conclude that in normal donors, filgrastim 10 micrograms/kg/d for 5 days with a single leukapheresis on the following day is a highly effective regimen for PBPC mobilization and collection. Further studies are required to determine whether PBPC collected with this regimen reliably produce rapid and sustained engraftment in allogeneic recipients.

The effect of cytokines on CD34+ Rh-123high and low progenitor cells from human umbilical cord blood

In this study, we show how Rhodamine-123 (Rh-123), as in other hematopoietic populations, can be used to define functionally distinct progenitor cells from human umbilical cord blood (HUCB). CD34+ cells were subdivided into Rh-123high (78.2 +/- 4.5%) and Rh-123low (21.8 +/- 3.6%). While 9.3 +/- 1.6% of the CD34+Rh-123high cells formed colonies in agar, only 0.4 +/- 0.2% of the CD34+Rh-123low population did so. However, the CD34+Rh-123low cells resulted in the greatest expansion of colony-forming cells (CFC) when cultured in liquid medium with different cytokine combinations. When the CD34+Rh-123low cells were cultured for 7 days with stem cell factor (SCF) and erythropoietin (Epo), the CD34+Rh-123low cells resulted in a 94-fold increase in CFC compared with a 2.5-fold increase from the CD34+Rh-123high cells. The combination of SCF and Epo or granulocyte-macrophage colony-stimulating factor (GM-CSF) supported the production and maintenance of CFC from CD34+Rh-123low cells > 28 days compared with only 21 days for the CD34+Rh-123high cells. Coculture of CD34+Rh-123low cells with stromal cell line 11 (SCL11) demonstrated that long-term culture initiating cells (LTCIC) were present within this population, as CFC could be recovered for > 10 weeks compared with < 6 weeks in cocultures with CD34+Rh-123high cells. The duration of maintenance of CFC in liquid culture could be further enhanced by the addition of an antibody (Ab) directed against the binding site of the GM-CSF receptor. The addition of anti-GM-CSF receptor Ab to cultures of CD34+Rh-123high and low cells supplemented with SCF, interleukin-3 (IL-3), and IL-6 resulted in an initial 10-fold decrease in CFC in cultures of both the CD34+Rh-123high and low cells. Although very few CFCs were present by 42 days in liquid cultures of CD34+Rh-123high cells, the number of CFCs in these cultures was significantly increased when anti-GM-CSF receptor Ab was added. Although this effect was also observed in cultures of CD34+Rh-123low cells, it was less dramatic as more CFC persisted even in the absence of Ab. The possible mechanism of this effect is discussed.

Combined chemotherapy and granulocyte colony-stimulating factor (G-CSF) mobilise large numbers of peripheral blood progenitor cells in pretreated patients

The aim of this study was to examine the effect of G-CSF given after salvage chemotherapy on the mobilisation of peripheral blood progenitor cells (PBPC) in pretreated patients. Seven patients with relapsed or refractory non-Hodgkin's lymphoma (NHL) were treated with methotrexate, cyclophosphamide, cytarabine, etoposide and dexamethasone. G-CSF was given at a dose of 3.8-7.2 micrograms/kg (1-2 ampoules) daily by subcutaneous injection from the onset of neutropenia (< 1.0 x 10(9)/L). A median of 3 leukaphereses was performed when the white cell count was recovering. The median number of granulocyte-macrophage colony-forming cells (GM-CFC) collected was 99 x 10(4)/kg per leucapheresis (range 19-800) or 260 x 10(4)/kg in total per patient (110-1800). Six patients underwent myeloablative chemotherapy with PBPC rescue. No autologous bone marrow or growth factors post-PBPC infusion were administered. The median duration of severe neutropenia (< 0.5 x 10(9)/L) was 8.5 days (range 5-10) and to recovery of neutrophils post-PBPC infusion was 11.5 days (10-15). Severe thrombocytopenia (< 20 x 10(9)/L) was present for 4 days (range 1-5) and the median number of days post-infusion to platelet-transfusion independence was 9 (6-12). In conclusion, G-CSF combined with chemotherapy mobilised large numbers of PBPC for subsequent autotransplantation in pretreated patients with NHL. A single leukapheresis procedure may be sufficient following this protocol.

Assessment of CD4 expression by early T precursor cells and by dendritic cells in the human thymus

The adult mouse thymus contains a minute population of early lymphoid precursor cells that express moderate levels of CD4. We searched for a corresponding population of early T precursors in the infant human thymus, by first depleting the majority of more mature thymocytes, then using immunofluorescence and flow cytometry to analyze cells bearing a range of early T lineage markers. No discrete population of early T precursors expressing CD4 was observed, in contrast to the murine thymus. Most putative very early human thymocytes were CD4-8-3-1-2lo44+34+7hi class I MHChi class II MHC-. However, a distinct population of human thymic dendritic cells expressing high levels of CD4 was isolated. These were CD4hi8-3-1-2-44+34-7- class I MHChi class II MHChi, and lacked markers of B cells, NK cells, or myeloid cells. They were large cells that exhibited dendritic morphology after brief periods of culture, and they were efficient stimulators of allogeneic T cells. The biologic implications of CD4 expression by thymic dendritic cells are discussed.

Assessment of CD4 expression by early T precursor cells and by dendritic cells in the human thymus

The adult mouse thymus contains a minute population of early lymphoid precursor cells that express moderate levels of CD4. We searched for a corresponding population of early T precursors in the infant human thymus, by first depleting the majority of more mature thymocytes, then using immunofluorescence and flow cytometry to analyze cells bearing a range of early T lineage markers. No discrete population of early T precursors expressing CD4 was observed, in contrast to the murine thymus. Most putative very early human thymocytes were CD4-8-3-1-2lo44+34+7hi class I MHChi class II MHC-. However, a distinct population of human thymic dendritic cells expressing high levels of CD4 was isolated. These were CD4hi8-3-1-2-44+34-7- class I MHChi class II MHChi, and lacked markers of B cells, NK cells, or myeloid cells. They were large cells that exhibited dendritic morphology after brief periods of culture, and they were efficient stimulators of allogeneic T cells. The biologic implications of CD4 expression by thymic dendritic cells are discussed.

A study of granular lymphoproliferative disorders including a CD3 negative case with a rearrangement of the T-cell receptor locus

The clinical, and laboratory features of 9 patients presenting with chronic proliferations of large granular lymphocytes (LGL) are described. The median patient age was 61 years (33-80) and median patient follow up was 3.5 years (28 mo-10 years) with all patients surviving. Clinical features and blood and bone marrow findings are documented. Immunophenotypic analysis showed lymphocytes from 4 patients were CD3 negative and 5 were CD3 positive with natural killer associated cell surface antigens expressed in both these groups. Analysis of the T-cell receptor (TCR) loci revealed a clonal rearrangement in 4 samples including one CD3 negative sample. Clonality did not correlate with immunophenotype or clinical or haematological features. We conclude that patients with persistent LGL have a wide diversity of cell surface marker expression and that whilst some patients with CD3 negative LGL proliferations have cells which are most likely of natural killer (NK) cell origin, in others TCR rearrangements can be demonstrated suggesting these cells are possibly of T-cell, not NK cell, origin.

Cytokine induction of adhesion molecules on synovial type B cells

OBJECTIVES

To study the role of cytokines on adhesion molecule expression and binding of activated T cells to synovial type B cells.

METHODS

Adhesion molecule expression was examined by immunofluorescence and adhesion of 51Cr-labelled T cells to the synovial cells determined.

RESULTS

Tumor necrosis factor alpha/interferon gamma (TNF alpha/IFN-gamma) and interleukin 1 alpha (IL-1 alpha)/IFN-gamma enhanced adhesion molecule expression and the adhesion of T cells to synovial cells. Anti-intercellular adhesion molecule 1 blocked adhesion of T cells to TNF alpha/IFN-gamma and IL-1 alpha/IFN-gamma stimulated synovial cells while an antibody to CD61 blocked adhesion to IL-1 alpha/IFN-gamma stimulated cells.

CONCLUSIONS

The interaction of leukocytes with adhesion molecules on synovial cells may play a role in recruitment of these cells to an inflammatory site.

Self-renewal of a transplantable murine leukemia induced by co-culture with human stromal cell lines

The PGM-1 murine leukemic cell line can be serially transplanted in syngeneic C3H/HeJ mice but cannot be maintained in in vitro culture. In response to a wide range of known growth factors, the PGM-1 cells either die or differentiate into mature granulocytes and macrophages with loss of all clonogenic (i.e. agar culture colony-forming) cells within 7 days. In this report we show that coculture with human, but not mouse, bone marrow stromal cell lines allows maintenance of clonogenic cells. One line in particular (197/17) allowed continuous expansion of clonogenic cells with no evidence of differentiation. The maintenance of clonogenic cells correlated with maintenance of tumor stem cells. Even after 9 months continuous passaging on stromal cells, the cultured cells produced tumors on injection into syngeneic mice with the same latency as cells from explanted tumors. We demonstrated that this activity was due to a soluble factor in 197/17 conditioned medium. An extensive survey of known factors, either alone or in combination, failed to reproduce this effect, implying that the effect was due to a novel factor acting on self-renewal of early stem cells.

Localization of a human receptor tyrosine kinase (ETK1) to chromosome region 3p11.2

We have recently described a human receptor tyrosine kinase (hek) that is expressed by some pre-B and thymic T cell lines, but is not detectable on normal adult human tissues. Gene cloning studies established that hek is a new member of the EPH family of receptor tyrosine kinases. The expression of hek may normally be developmentally regulated and inappropriate expression may contribute to oncogenesis. In the present study, we have used Southern blot analysis of somatic cell hybrids and fluorescence in situ hybridization to localize the hek gene to human chromosome region 3p11.2. Karyotype analysis of the cell lines that over-express hek showed no cytogenetically visible abnormality involving the hek locus.

Hemopoietic and lymphoid progenitor cells in human umbilical cord blood

Human umbilical cord blood, which in the past was discarded with the placental tissue, provides a convenient source of fetal hemopoietic cells for scientific analysis and clinical use. Cord blood cells are immature compared to analogous populations in adult peripheral blood. Cord blood B lymphocytes display unique phenotypic and functional characteristics. The antigens CD1C, CD38, CD5, and CD23, although normally expressed on only a small percentage of circulating B cells in adults, are highly expressed on cord blood B cells. Recent studies have demonstrated that whereas cord blood B cells are functionally naive, their potential is similar to that of adult B cells if optimal T-cell help is available. Thus, the failure of B-cell responses in cord blood is due to the T cells. The functional abnormalities of T cells from newborns can be summarized as a dominance of the effects of TH0 cells. Thus, the cytokines produced are immunosuppressive rather than mediating helper activity for B cells. NK activity in cord blood is also depressed compared to that in adults. Cord blood is a very rich source of hemopoietic progenitor cells. The spectrum of progenitors shows a predominance of early progenitor cells when compared with bone marrow. These cells provide an alternative source to adult bone marrow for stem cells to use for hemopoietic reconstitution and as targets in the treatment of hereditary deficiencies by gene therapy. These features make cord blood a unique research tool to investigate hemopoietic ontogeny and a unique clinical tool for transplantation.

Characterization of CD34+HLA-DR-CD38+ and CD34+HLA-DR-CD38- progenitor cells from human umbilical cord blood

In this study we show that depletion of cells expressing mature cell markers, including HLA-DR, followed by positive cell sorting for cells expressing CD34 and CD38, can be used to define functionally distinct hematopoietic cells from human umbilical cord blood (HUCB). The CD34+HLA-DR-CD38+ population contained the majority of directly clonogenic cells, while the optimal ability to maintain long term co-culture with bone marrow stromal cells was present within the CD34+HLA-DR-CD38- population. 1.2 +/- 0.4% of the CD34+HLA-DR-CD38- cells plated at 1 cell/well and grown in the presence of hematopoietic growth factors (HGF) formed hemopoietic colonies. Mesenchymal elements were observed in 20% of these cultures. No cell growth, however, was observed when the CD34+HLA-DR-CD38- cells were cultured in the absence of HGF. This is in contrast with the findings in fetal bone marrow which demonstrated the presence of stem cells that were independent of HGF. Thus, while it is possible to isolate very immature hemopoietic progenitor cells from HUCB defined by the phenotype Lin-CD34+HLA-DR-CD38-, these cells do not appear to exhibit the pluripotentiality of the analogous population reported in fetal bone marrow. We conclude that these cells are absent or at a very small frequency in HUCB.

Neutralizing and nonneutralizing monoclonal antibodies to the human granulocyte-macrophage colony-stimulating factor receptor alpha-chain

A panel of monoclonal antibodies was raised against the low-affinity human granulocyte-macrophage colony-stimulating factor (hGM-CSF) receptor alpha-chain expressed as recombinant protein on murine FDC-P1 cells. All the selected antibodies were of the IgG2A isotype and bound to protein A. They each recognized both native and recombinant receptors by indirect surface immunofluorescence and by immunoprecipitation. Several of the antibodies also recognized presumably denatured receptors as detected by immunoblotting of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Three different epitopes on the extracellular domain of the GM-CSF receptor alpha-chain were defined by these antibodies, and two of the epitopes did not appear to be involved in binding hGM-CSF or in interactions with the beta-chain of the GM-CSF receptor that are required for high-affinity binding of GM-CSF. On the other hand, the epitope recognized by antibody 2B7-17-A appeared to be critically involved in the binding of GM-CSF because this antibody completely abrogated both high- and low-affinity binding of GM-CSF to native and recombinant receptors. Antibody 2B7-17-A had a relatively high affinity for the GM-CSF receptor alpha-chain (kd = 3 nmol/L) and slow dissociation kinetics (kd = 0.002 min-1). These properties made the 2B7-17-A antibody a potent inhibitor of hGM-CSF biologic action in several different bioassays, with a half-maximal inhibitory dose of about 6 nmol/L (1 microgram/mL). This antibody could prove useful in alleviating any pathologic states mediated by excess GM-CSF levels and in defining the domains of the GM-CSF receptor required for ligand binding.

Synthetic peptide analogs of intercellular adhesion molecule 1 (ICAM-1) inhibit HIV-1 replication in MT-2 cells

On the basis of reports demonstrating possible roles for leukocyte function-associated antigen 1 (LFA-1) and intercellular adhesion molecule 1 (ICAM-1), the ligand for LFA-1, in human immunodeficiency virus type 1 (HIV-1) infection, we have explored the involvement of the ICAM-1 molecule by using selected synthetic peptides derived from the protein sequence. Replication was assessed in MT-2 cells, highly susceptible to HIV infection, in the presence of four synthetic peptides derived from the ICAM-1 amino acid sequence. This cell type was chosen for the ability to form marked syncytia on infection with cell-free virus. Under the conditions used, minimal or no cytotoxicity was observed with the peptides up to concentrations of 50 micrograms/ml. A peptide corresponding to a unique region of ICAM-1, JF9 [ICAM-1(367-394, A-378)], had little effect on virus replication despite its ability to inhibit cell-cell adhesion. In contrast, an N-terminal peptide, JF7B [ICAM-1(1-23)], consistently inhibited virus replication in MT-2 cells in a dose-dependent manner, as measured by cell-free reverse transcriptase (RT) activity (up to 70% inhibition), soluble virus antigen production (up to 60% inhibition), and syncytium formation (virtually complete inhibition up to 6 days post infection). Testing of W-CAM-1 antibody, and anti-ICAM-1 antibody that inhibits cell-cell adhesion, revealed no significant inhibitory effects on RT activity, virus antigen production, and syncytium formation in HIV-1-infected MT-2 cells at a level that markedly inhibited cell-cell adhesion (10 micrograms/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokine production in response to Epstein-Barr virus infection of peripheral blood mononuclear cells in vitro

To obtain a better understanding of the immune response to Epstein-Barr virus (EBV), we measured the cytokines tumour necrosis factor (TNF)-alpha/beta, interleukin-2 (IL-2), interferon-gamma (IFN-gamma), IL-6 and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the conditioned medium of peripheral blood mononuclear cells from 10 healthy adults before and at 48 h and at 1, 2, 3 and 4 weeks following infection in vitro with EBV. Cultures were examined for regression of outgrowths of nascent virus-transformed B cells, and populations of cells in the cultures were analysed by flow cytometry. TNF-alpha/beta was not detected in infected or non-infected cultures. In infected cultures assayed at the nominated times, the highest levels of IL-2 were detected at 48 hours, IFN-gamma at 1 week, IL-6 at 2 weeks and GM-CSF between 2 and 4 weeks. IL-6 and GM-CSF, but not IL-2 or IFN-gamma, were detected in non-infected cultures but at lower levels than in infected cultures. Nine of the 10 healthy adults showed regression of outgrowths of virus-transformed B cells and, of these, seven had antibodies to the EBV capsid antigen (VCA). Strong regression was associated with sequential increases in IL-2, IFN-gamma, and low levels of IL-6 and GM-CSF. Absent or weak regression was associated with an undetectable level of IL-2, a low level of IFN-gamma, high levels of IL-6 and GM-CSF and an increased frequency of cells bearing the phenotype CD20 and HLA-DR in the final weeks of culture.(ABSTRACT TRUNCATED AT 250 WORDS)

A novel population of natural killer progenitor cells isolated from human umbilical cord blood

In this report, we describe the isolation of a unique subpopulation of CD7+ cells from human fetal blood. Umbilical cord blood was first immuno-rosette-depleted using T cell, B cell, granulocyte, and macrophage markers to isolate a Lin- population. The Lin- cells were further characterized by cell sorting. As expected, the CD34+Lin- population (30%) was homogeneous and highly enriched for hemopoietic progenitors. Somewhat surprisingly, the CD34-Lin- population was also shown to be relatively homogeneous, with over 95% of cells expressing CD7. This CD34-Lin-CD7+ population was shown to be negative for all other T cell markers tested (i.e., CD7+1-2-3-4-8-). However, approximately 30% of these cells were positive for the NK cell surface markers CD16 and CD56 (CD7+NK+). Both CD7+NK+ and CD7+NK- populations proliferated in response to stimulation in vitro with IL-2/PHA/PHA-conditioned medium. After such treatment, approximately 40% of the CD7+NK- acquired CD56 and 20% CD16, whereas about 20% of the CD7+NK+ population became CD2+. The significance of the 60% of CD7+NK- cells that did not acquire other markers remains to be determined. In addition, although neither population was cytotoxic when first isolated, both populations acquired the ability to lyse the NK target cell line K562 while cultured under these conditions. These data suggest that these two populations may represent a developmental sequence among NK cell precursors in human umbilical cord blood. Additional analysis of such precursors may be useful in understanding the ontogeny of NK cells in vivo.

A novel population of natural killer progenitor cells isolated from human umbilical cord blood

In this report, we describe the isolation of a unique subpopulation of CD7+ cells from human fetal blood. Umbilical cord blood was first immuno-rosette-depleted using T cell, B cell, granulocyte, and macrophage markers to isolate a Lin- population. The Lin- cells were further characterized by cell sorting. As expected, the CD34+Lin- population (30%) was homogeneous and highly enriched for hemopoietic progenitors. Somewhat surprisingly, the CD34-Lin- population was also shown to be relatively homogeneous, with over 95% of cells expressing CD7. This CD34-Lin-CD7+ population was shown to be negative for all other T cell markers tested (i.e., CD7+1-2-3-4-8-). However, approximately 30% of these cells were positive for the NK cell surface markers CD16 and CD56 (CD7+NK+). Both CD7+NK+ and CD7+NK- populations proliferated in response to stimulation in vitro with IL-2/PHA/PHA-conditioned medium. After such treatment, approximately 40% of the CD7+NK- acquired CD56 and 20% CD16, whereas about 20% of the CD7+NK+ population became CD2+. The significance of the 60% of CD7+NK- cells that did not acquire other markers remains to be determined. In addition, although neither population was cytotoxic when first isolated, both populations acquired the ability to lyse the NK target cell line K562 while cultured under these conditions. These data suggest that these two populations may represent a developmental sequence among NK cell precursors in human umbilical cord blood. Additional analysis of such precursors may be useful in understanding the ontogeny of NK cells in vivo.

Interactions between purified human cord blood haemopoietic progenitor cells and accessory cells

The role of accessory cells in haemopoiesis remains confused. This appears in large part to reflect the use of impure populations of accessory cells and progenitor cells in previous studies. In this study, cell sorter purified populations of both accessory cells and haemopoietic progenitor cells were used to examine interactions between these cell types. We used a double culture protocol in which purified CD34+ cells were cultured with purified NK, T or monocytic cells in the first liquid culture phase after which the cells were transferred to secondary agar cultures to determine the number of colony forming cells (CFC). NK cells co-cultured with CD34+ cells resulted in an increased number of erythroid progenitors with no effect on the number of nonerythroid progenitors. In contrast, there were increased numbers of erythroid and non-erythroid CFC when the CD34+ cells were co-cultured with either purified T cells or monocytes. CD34+ cells cultured with cell-conditioned media derived from NK cells, T cells or monocytes in transwells where the CD34+ cells and the accessory cells were separated by a 0.2 micron membrane, showed no enhancement in CFC. These results suggest that intimate cell-cell contact is required for these events.