Author Correction: Nearly all the sky is covered by Lyman-α emission around high-redshift galaxies.

Change history: In this Letter, author M. Akhlaghi should be associated with affiliation (2) rather than (3). This error has been corrected online.

Nearly all the sky is covered by Lyman-α emission around high-redshift galaxies.

Galaxies are surrounded by large reservoirs of gas, mostly hydrogen, that are fed by inflows from the intergalactic medium and by outflows from galactic winds. Absorption-line measurements along the lines of sight to bright and rare background quasars indicate that this circumgalactic medium extends far beyond the starlight seen in galaxies, but very little is known about its spatial distribution. The Lyman-α transition of atomic hydrogen at a wavelength of 121.6 nanometres is an important tracer of warm (about 104 kelvin) gas in and around galaxies, especially at cosmological redshifts greater than about 1.6 at which the spectral line becomes observable from the ground. Tracing cosmic hydrogen through its Lyman-α emission has been a long-standing goal of observational astrophysics1-3, but the extremely low surface brightness of the spatially extended emission is a formidable obstacle. A new window into circumgalactic environments was recently opened by the discovery of ubiquitous extended Lyman-α emission from hydrogen around high-redshift galaxies4,5. Such measurements were previously limited to especially favourable systems6-8 or to the use of massive statistical averaging9,10 because of the faintness of this emission. Here we report observations of low-surface-brightness Lyman-α emission surrounding faint galaxies at redshifts between 3 and 6. We find that the projected sky coverage approaches 100 per cent. The corresponding rate of incidence (the mean number of Lyman-α emitters penetrated by any arbitrary line of sight) is well above unity and similar to the incidence rate of high-column-density absorbers frequently detected in the spectra of distant quasars11-14. This similarity suggests that most circumgalactic atomic hydrogen at these redshifts has now been detected in emission.

Treatment with autologous bone marrow mononuclear cells in patients with critical lower limb ischaemia. A pilot study.

BACKGROUND AND AIMS: Treatment with autologous, bone marrow mononuclear stem cells has shown effects in patients with chronic limb ischaemia in one randomized clinical study. The aim of the study was to test the potential effect of stem cell treatment in a strict defined group of patients with stable critical limb ischaemia (CLI). DESIGN: A prospective, combined-centre pilot study. MATERIAL: Eight patients with CLI of the lower extremities, and without any other treatment options. METHODS: Bone marrow cells were harvested from the patient's iliac crest and, after separation, injected into the calf muscles of the affected leg. Outcome was evaluated by digital subtraction angiography (DSA), visual analogue scale (VAS) and several non-invasive circulatory physiological tests. RESULTS: There were no complications from the procedures. Two patients were amputated two months after cell injection. Five patients reported pain relief after four months. Five patients could be evaluated at eight months. According to VAS and physiological tests, they were all either stable or showed improvement. CONCLUSION: This method seems to be a safe option for treating patients with CLI. Inclusion of patients took a long time, mainly because many patients with CLI are offered endovascular treatment in our institution. While symptomatic improvement was found in individual patients, larger trials are required to investigate efficacy. This will probably require multi-centre participation.

Differential propagation of stroma and cancer stem cells dictates tumorigenesis and multipotency.

Glioblastoma Multiforme (GBM) is characterized by high cancer cell heterogeneity and the presence of a complex tumor microenvironment. Those factors are a key obstacle for the treatment of this tumor type. To model the disease in mice, the current strategy is to grow GBM cells in serum-free non-adherent condition, which maintains their tumor-initiating potential. However, the so-generated tumors are histologically different from the one of origin. In this work, we performed high-throughput marker expression analysis and investigated the tumorigenicity of GBM cells enriched under different culture conditions. We identified a marker panel that distinguished tumorigenic sphere cultures from non-tumorigenic serum cultures (high CD56, SOX2, SOX9, and low CD105, CD248, αSMA). Contrary to previous work, we found that 'mixed cell cultures' grown in serum conditions are tumorigenic and express cancer stem cell (CSC) markers. As well, 1% serum plus bFGF and TGF-α preserved the tumorigenicity of sphere cultures and induced epithelial-to-mesenchymal transition gene expression. Furthermore, we identified 12 genes that could replace the 840 genes of The Cancer Genome Atlas (TCGA) used for GBM-subtyping. Our data suggest that the tumorigenicity of GBM cultures depend on cell culture strategies that retain CSCs in culture rather than the presence of serum in the cell culture medium.

Reduced CD4 cell counts in blood do not reflect CD4 cell depletion in tonsillar tissue in asymptomatic HIV-1 infection.

OBJECTIVE: To investigate whether the loss of CD4 cells seen in peripheral circulation of HIV-1-positive individuals reflects a similar depletion of CD4 cells from lymphoid tissue. DESIGN: CD4 and CD8 cells in tonsillar mononuclear cell suspensions were quantified relative to tonsillar B cells, as these were thought to remain numerically unchanged in the course of HIV infection. Results were related to the CD4 cell counts in blood and to the clinical status of the patients. METHODS: Blood samples and tonsillar tissue were obtained from 13 HIV-1-seropositive individuals and six seronegative controls. B cells and T-cell subsets in mononuclear cells were quantified using a three-colour flow cytometry protocol. Histological sections were morphologically classified and B-cell areas were quantified by morphometry. RESULTS: The B-cell fraction was confirmed to be relatively unchanged in asymptomatic HIV-1-seropositive individuals compared with controls. The tonsillar CD4 : B-cell ratios in asymptomatic individuals was similar to those seen in controls, whereas the CD4 : B-cell ratios in symptomatic HIV-1-infected individuals were greatly reduced. The tonsillar CD4 : CD8 cell ratios in HIV-1-infected individuals were much lower than those seen in controls, in the asymptomatic group due to a considerable expansion of the tonsillar CD8 cell subset, and in the symptomatic group also due to a loss of CD4 cells. CONCLUSIONS: We found no evidence of CD4 cell depletion in tonsillar tissue in asymptomatic HIV-1-infected individuals despite low CD4 cell counts in blood. Loss of CD4 cells from this lymphoid tissue seems to occur as a late-stage phenomenon correlated with the onset of clinical symptoms.

Normal CD4 T-cell receptor repertoire in tonsillar tissue despite perturbed repertoire in peripheral blood in HIV-1 infected individuals.

OBJECTIVE: To compare the T-cell receptor (TCR) repertoire of T-cell subsets in peripheral blood and lymphoid tissue from HIV-1 infected individuals. DESIGN: Biopsies of tonsillar tissue and samples of peripheral blood were obtained from 10, mostly treatment-naive, HIV-1-infected individuals. CD4 and CD8 T-cell subsets were quantified, the TCR repertoire was analysed within 'naive' and 'memory' subsets, and results compared between identical subsets in tonsillar tissue and blood. METHODS: Cell subsets were quantified by flow cytometry. CD4 T cells and CD8 T cells were isolated by immunomagnetic beads. Populations were in most cases further subdivided by immunomagnetic selection on the basis of CD45RO expression. TCR repertoire was studied by spectratyping of the TCR beta variable (BV) complementarity determining region 3 (CDR3) transcripts. RESULTS: Amongst CD4 T cells, an abnormal TCR repertoire was found in median 25% (range, 0-88%) of BV families in peripheral blood, but in 0% (0-7%) in tonsillar tissue (P<0.05). Large peaks suggestive of expanded clones were common within CD8 T-cells, both in peripheral blood and tonsillar tissue. However, the expanded clones were rarely identical in the two compartments. Expanded CDR3 peaks, suggesting the presence of clonally expanded cells, were observed within both CD45RO+ and CD45RO- cells from all T-cell subsets, but, again they were mainly of different lengths. CONCLUSION: CD4 T cells were preserved in number and TCR repertoire in tonsillar tissue compared with blood in HIV-1 infected individuals. T-cells collected from the peripheral blood may not be representative of those residing in lymphoid tissue.

In vitro replication of HIV-1 in naturally infected CD4+ T cells is inhibited by rIFN alpha 2 and by a soluble factor secreted by activated CD8+ T cells, but not by rIFN beta, rIFN gamma, or recombinant tumor necrosis factor-alpha.

The effect of lymphokines on the replication of HIV-1 has previously been investigated using HIV-1-infected cell lines or PBMCs infected in vitro with HIV-1. We have examined the effect of rIFN alpha 2, rFIN beta, and rIFN gamma and recombinant tumor necrosis factor-alpha (rTNF alpha) on the replication of HIV-1 in vitro in naturally HIV-1-infected CD4+ T cells from asymptomatic HIV-1-seropositive individuals. rIFN alpha 2 inhibited the replication of HIV-1 effectively at concentrations that can be achieved in vivo. The inhibitory activity was most efficacious when rIFN alpha 2 was added as the CD4+ T cells were being activated, and less but still considerable when rIFN alpha 2 was added 4-96 h after CD4+ T-cell activation. rIFN alpha 2 exerted a suppressive effect on the proliferation of the CD4+ T cells, but this effect was small at concentrations that caused 90% inhibition of the replication of HIV-1. rIFN beta, rIFN gamma, and rTNF alpha had no effect on the replication of HIV-1, but rIFN beta and rTNF alpha had a costimulatory effect on CD4+ T-cell proliferation. Activated CD8+ T cells secrete a HIV-1-inhibitory soluble factor. Blocking experiments using an IFN alpha 2-neutralizing MAb showed that this HIV-1-inhibitory factor is not IFN alpha 2.

T lymphocyte subset changes in human immunodeficiency virus infection.

The absolute number of CD4+ and CD8+ T cells was determined by an immunomagnetic technique directly in the blood of 75 healthy controls and 223 HIV-infected individuals. The HIV-seropositive individuals were also classified clinically according to the system recommended by the Centers for Disease Control (CDC), and the CDC classification was correlated with the patients' T cell subset counts. Compared to the control group, the HIV-infected individuals demonstrated an early and sustained increase in the number of CD8+ T cells with median values of CDC groups II, III, and IV C2 twice that observed in the control group. Patients with AIDS had CD8+ T cell counts comparable to those of the control group. The HIV-infected individuals showed a decrease in the number of CD4+ T cells correlating with clinical deterioration of the disease. T cell subset counts significantly distinguished the group of healthy seropositive individuals from those with HIV-related disease, and the group of patients with AIDS from those with other HIV-related opportunistic infections.

Analysis of alloreactive helper T lymphocyte precursor frequencies. Influence of interleukin-2 produced by the stimulating cells.

In the determination of alloreactive helper T lymphocyte precursor frequencies (HTLpf) by limiting dilution analysis (LDA), peripheral blood mononuclear cells (PBMC) are used as stimulating cells. Interleukin-2 (IL-2) production by stimulating T cells constitute a source of error in these assays. We found that 100-150 Gy of gamma irradiation was required to abrogate IL-2 production by stimulating PBMC. This dose of irradiation, however, greatly reduced their allostimulatory capability. Here we describe how non-irradiated PBMC, immunomagnetically depleted of T cells and thus of IL-2 producing cells, can be used as stimulators in assays to determine alloresponsive HTLpf.

Molecular analysis of the complementarity determining region 3 of the human T cell receptor beta chain. Establishment of a reference panel of CDR3 lengths from phytohaemagglutinin activated lymphocytes.

The T cell receptor (TCR) repertoire of a lymphocyte population may be characterized by the distribution of lengths of the hypervariable fragment known as the complementarity determining region 3 (CDR3). Immunological activity leading to clonal predominance will result in an over-representation of given CDR3 lengths and a distortion of the CDR3 length distribution. CDR3 length distribution may be studied by the in vitro amplification of TCRB cDNA followed by gel electrophoresis of the resulting product. We have established a simple, robust method for the evaluation of CDR3 length distribution in human lymphocyte samples. The CDR3 length distribution in phytohaemagglutinin (PHA) activated lymphocytes from a large number of healthy donors was established as a reference panel for each of 22 human TCR beta variable (BV) families. We propose that an abnormal CDR3 length distribution be defined as one in which one or more CDR3 lengths exceed the upper confidence limit (5% significance, one-sided test) given by this PHA reference population. Using this criterion in titration experiments, we were able to identify a clone when it constituted 2% of the cells analyzed. Over-dilution of cellular material or cDNA may produce falsely abnormal CDR3 length distributions. A nested technique using two separate amplification steps was found to yield results comparable in quality to the single amplification technique. When few cells are available, the nested method gives more material for CDR3 length analyses. However, it does not reduce the likelihood of a falsely abnormal distribution being recorded when the cellular material is too scarce.

In vivo expansion coincident with excessive in vitro cell death within the memory subset of CD8+ T cells in HIV type 1 infection.

In HIV-1-infected individuals the CD8+ T cell subset is considerably expanded. This has been shown to be caused predominantly by an increase in the number of CD8+CD28- T cells. To characterize further the subsets of CD8+ T cells, we have performed analyses of cell surface phenotype, T cell receptor Vbeta usage, and ability to survive in unstimulated cultures. CD8+CD28- T cells frequently expressed CD45RA. Nonetheless, coincident expression of CD95 (Fas) and high levels of integrins suggested that these cells were immunologically experienced. Contrary to what has been observed in CD8+CD28- T cells from uninfected individuals, a common hierarchy of Vbeta usage was found in CD8+CD28- T cells from HIV-1-infected individuals, which was adhered to by all the study participants, and which was shown to be similar to that observed within CD8+CD28+ T cells. Cells from the memory subsets of CD8+ T cells showed a high incidence of spontaneous death in unstimulated cultures, indicating that these cells have received signals for death by apoptosis in vivo. In contrast, most naive CD8+CD28+CD45RA+ cells survived. The CD8+CD28- memory subset is expanded in vivo despite evidence for coincident excessive cell death in vitro. Our results are consistent with the notion that frequent transitions occur from the memory CD8+CD28+CD45RA- T cell subset to the end-stage CD8+CD28- subset during HIV-1 infection.

CD8+ T cells from HIV type 1-seronegative individuals suppress virus replication in acutely infected cells.

CD8+ lymphocytes (CD8 cells) have been shown to inhibit replication of the human immunodeficiency virus (HIV) in vitro when cocultured with HIV-infected CD4+ lymphocytes (CD4 cells). This suppressive effect on HIV replication in experimentally infected CD4 cells has so far been demonstrated only for CD8 cells from HIV-seropositive individuals. In the present study we have investigated if CD8 cells from HIV-negative individuals can also suppress HIV replication in experimentally infected CD4 cells. Positively selected CD4 cells were infected with phenotypically different primary isolates of HIV type 1 and 2 (HIV-1 and HIV-2). Graded numbers of CD8 cells were added to the infected cultures. The T cells were activated by antibodies directed against the CD3 molecule or the T cell receptor. Culture supernatants were harvested for HIV p24 quantitation and the CD8 suppression of HIV replication was calculated by comparing p24 levels from parallel cultures in the presence or absence of CD8 cells from different donors. We show that CD8 cells from unexposed HIV-seronegative blood donors are able to control HIV-1 and HIV-2 replication in experimentally infected autologous CD4 cells. The antiviral activity of CD8 cells from and HIV-naive individual was reproducible over time and the suppressive effect was comparable to that seen with CD8 cells from HIV-positive individuals. The infected cells were not eliminated from the cultures. The suppressive effect of CD8 cells varied depending on the dose and biological phenotype of the virus used for infection. Thus, exposure to HIV in vivo is not a prerequisite for CD8 cells to exert a suppressive effect on HIV replication in acutely infected cells.

Correlates of apoptosis of CD4+ and CD8+ T cells in tonsillar tissue in HIV type 1 infection.

The immunopathogenesis of human immunodeficiency virus type 1 (HIV-1) infection has been associated with increased death by apoptosis of T cell subsets. In the present study, we have examined correlates of apoptosis of CD4+, CD8S+CD28+, and CD8+CD28- T cells in tonsillar lymphoid tissue in persons with HIV-1. Single-cell suspensions of tonsillar lymphocytes were analyzed by flow cytometry to determine the fraction of cells showing typical characteristics of apoptosis as well as the expression of activation markers within the live and the apoptotic cell populations. The proportion of cells carrying infectious provirus was quantified by limiting dilution analysis. Compared with uninfected controls, apoptosis of both CD4+ and CD8+ T cells was enhanced in HIV-1 infection and was higher among CD8+ than among CD4+ T cells. Apoptosis of CD28-cells was more prevalent than apoptosis of CD28+ cells for both CD4+ and CD8+ T cells. Occurrence of apoptosis of CD4+ T cells correlated with provirus levels and proportional expression of the activation marker HLA-DR. Apoptosis of CD8+CD28+ cells correlated with expression of the activation markers CD69 and HLA-DR while apoptosis within CD8+CD28- cells did not correlate with any of the studied parameters. Although apoptosis was much more prevalent among CD8+ than CD4+ T cells, CD8+ T cells still accumulated in tonsillar lymphoid tissue in persons with HIV-1. Our data may be interpreted to suggest that apoptosis of CD4+, CD8+CD28+, and CD8+CD28- cells in tonsillar tissue is regulated by different mechanisms and the results are of importance to our understanding of the immunopathogenesis of HIV-1 infection.

Reliable isolation of human immunodeficiency virus from cultures of naturally infected CD4+ T cells.

A procedure for reliable and reproducible isolation of human immunodeficiency virus (HIV) from cultures of CD4+ T cells from healthy HIV seropositive individuals is described. Using immunomagnetic cell separation techniques, CD4+ T cells were positively selected from blood or peripheral blood mononuclear cells from 34 HIV infected individuals in CDC group II. The cells were stimulated with beads coated with a monoclonal antibody specific for the T cell receptor alpha/beta dimer and cultured in medium containing recombinant IL 2. HIV was isolated from 100% of the 41 cultures from 34 individuals. As this culture system allows reproducible isolation of HIV from cultures of naturally infected CD4+ T cells in the absence of other autologous or allogeneic cells, it may provide a good test system for the study of factors affecting the replication of HIV at low multiplicities of infection.

Long-term results after intracoronary injection of autologous mononuclear bone marrow cells in acute myocardial infarction: the ASTAMI randomised, controlled study.

OBJECTIVE: To investigate long-term safety and efficacy after intracoronary injection of autologous mononuclear bone marrow cells (mBMCs) in acute myocardial infarction (AMI). DESIGN: Randomised, controlled trial. SETTING: Two university hospitals in Oslo, Norway. PATIENTS: Patients from the Autologous Stem cell Transplantation in Acute Myocardial Infarction (ASTAMI) study were re-assessed 3 years after inclusion. INTERVENTIONS: 100 patients with anterior wall ST-elevation myocardial infarction treated with acute percutaneous coronary intervention (PCI) were randomised to receive intracoronary injection of mBMCs (n = 50) or not (n = 50). MAIN OUTCOME MEASURES: Change in left ventricular (LV) ejection fraction (primary). Change in exercise capacity (peak VO(2)) and quality of life (secondary). Infarct size (additional aim), and safety. RESULTS: The rates of adverse clinical events in the groups were low and equal. There were no significant differences between groups in change of global LV systolic function by echocardiography or magnetic resonance imaging (MRI) during the follow-up. On exercise testing, the mBMC-treated patients had larger improvement in exercise time from 2-3 weeks to 3 years (1.5 minutes vs 0.6 minutes, p = 0.05), but the change in peak oxygen consumption did not differ (3.0 ml/kg/min vs 3.1 ml/kg/min, p = 0.75). CONCLUSION: The results indicate that intracoronary mBMC treatment in AMI is safe in the long term. A small improvement in exercise time in the mBMC group was found, but no other effects of treatment could be identified 3 years after cell therapy.

Bone marrow mesenchymal stem cells in a hyaluronan scaffold for treatment of an osteochondral defect in a rabbit model.

The purpose of this study was to evaluate the efficiency of using mesenchymal stem cells (MSC) in a hyaluronan scaffold for repair of an osteochondral defect in rabbit knee. Bone marrow was harvested from the posterior iliac crest in 11 New Zealand White rabbits. MSC were isolated and cultured in autologous serum for 28 days and transferred to a hyaluronan scaffold 24 h prior to implantation. A 4 mm diameter and 1.5 mm deep defect was created in the medial femoral condyle of both knees and the scaffold with MSC was implanted in one knee while an empty scaffold was implanted in the contra-lateral knee. After 24 weeks the rabbits were killed and histological sections were subjected to semiquantitative and quantitative evaluation by observers blinded regarding treatment modality. High degree of filling was obtained, but there was no statistically significant difference between the two treatments. However, there was a tendency for a better quality of repair in the MSC treated knees. No hypertrophy was observed by either method. MSC in a hyaluronan scaffold may be a promising treatment approach, but further studies are needed to determine the best combination of scaffold and cells.

[Factors influencing the development of the HIV pandemic]. / Hvilke faktorer avgjør HIV-pandemiens utvikling?

The human immunodeficiency virus (HIV) is transmitted by unprotected sexual intercourse, via infected blood or blood products, or perinatally from mother to infant. A number of factors determine the risk of transmission in any of these situations. The general risk of infection in a society will also depend on the duration of the incubation period from infection to onset of HIV-related disease and death. This article discusses some of the factors which determine the risk of transmission, the general risk of infection in a society and the individual decision to engage in high-risk activities.