Lorenzo Moretti

Mesenchymal cells recruit and regulate T regulatory cells

OBJECTIVE Despite much investigation into T regulatory cells (Tregs), little is known about the mechanism controlling their recruitment and function. Because multipotent mesenchymal stromal cells (MSCs) exert an immune regulatory function and suppress T-cell proliferation, this in vitro study investigated their role in Treg recruitment and function. MATERIALS AND METHODS Human MSCs and different T cell populations (CD3(+), CD3(+)/CD45RA(+), CD3(+)/CD45RO(+), CD4(+)/CD25(+), CD4(+)/CD25(+)/CD45RO(+), CD4(+)/CD25(+)/CD45RA(+)) from healthy donors were cocultured for up to 15 days. Harvested lymphocytes were analyzed by flow cytometry and FoxP3 and CD127 expressions were measured by real-time polymerase chain reaction. Their regulatory activity was assessed. RESULTS We demonstrate MSC recruit Tregs from a fraction of CD3(+) and from immunoselected CD3(+)/CD45RA(+) and CD3(+)/CD45RO(+) fractions. After culture with MSCs both immunoselected fractions registered increases in the CD4(+)/CD25(bright)/FoxP3 subset and CD127 expression was downregulated. When purified Treg populations (CD4/CD25(+), CD4/CD25(+)/CD45RA(+), and CD4/CD25(+)/CD45RO(+)) are used in MSC cocultures, they maintain FoxP3 expression and CD127 expression is downregulated. Treg suppressive capacity was maintained in Treg populations that were layered on MSC for up to 15 days while control Tregs lost all suppressive activity after 5 days culture. CONCLUSIONS In conclusion, our study demonstrates that MSCs recruit, regulate, and maintain T-regulatory phenotype and function over time.

Immunomagnetic isolation of CD4+CD25+FoxP3+ natural T regulatory lymphocytes for clinical applications.

Although CD4+/CD25+ T regulatory cells (Tregs) are a potentially powerful tool in bone marrow transplantation, a prerequisite for clinical use is a cell‐separation strategy complying with good manufacturing practice guidelines. We isolated Tregs from standard leukapheresis products using double‐negative selection (anti‐CD8 and anti‐CD19 monoclonal antibodies) followed by positive selection (anti‐CD25 monoclonal antibody). The final cell fraction (CD4+/CD25+) showed a mean purity of 93·6% ± 1·1. Recovery efficiency was 81·52% ± 7·4. The CD4+/CD25+bright cells were 28·4% ± 6·8. The CD4+/CD25+ fraction contained a mean of 51·9% ± 15·1 FoxP3 cells and a mean of 18·9% ± 11·5 CD127 cells. Increased FoxP3 and depleted CD127 mRNAs in CD4+CD25+FoxP3+ cells were in line with flow cytometric results. In Vβ spectratyping the complexity scores of CD4+/CD25+ cells and CD4+/CD25‐ cells were not significantly different, indicating that Tregs had a broad T cell receptor repertoire. The inhibition assay showed that CD4+/CD25+ cells inhibited CD4+/CD25‐ cells in a dose‐dependent manner (mean inhibition percentages: 72·4 ± 8·9 [ratio of T responder (Tresp) to Tregs, 1:2]; 60·8% ± 20·5 (ratio of Tresp to Tregs, 1:1); 25·6 ± 19·6 (ratio of Tresp to Tregs, 1:0·1)). Our study shows that negative/positive Treg selection, performed using the CliniMACS device and reagents, enriches significantly CD4+CD25+FoxP3+ cells endowed with immunosuppressive capacities. The CD4+CD25+FoxP3+ population is a source of natural Treg cells that are depleted of CD8+ and CD4+/CD25‐ reacting clones which are potentially responsible for triggering graft‐versus‐host disease (GvHD). Cells isolated by means of this approach might be used in allogeneic haematopoietic cell transplantation to facilitate engraftment and reduce the incidence and severity of GvHD without abrogating the potential graft‐versus‐tumour effect.

MtDNA mutation associated with mitochondrial dysfunction in megakaryoblastic leukaemic cells

MtDNA mutation associated with mitochondrial dysfunction in megakaryoblastic leukaemic cells

A microelectronic DNA chip detects the V617F JAK-2 mutation in myeloproliferative disorders

A microelectronic DNA chip detects the V617F JAK-2 mutation in myeloproliferative disorders

NeoR-based transduced T lymphocytes detected by real-time quantitative polymerase chain reaction.

To develop a trial with lymphocyte suicide gene therapy in patients with hematological malignancies, we transduced human T lymphocytes with a retroviral vector (LSN-tk) encoding the herpes simplex virus thymidine kinase (tk) and the neomycin resistance (NeoR) genes. Precise quantification of gene transfer is crucial for any gene therapy protocol, but methods using semiquantitative PCR are inaccurate and subject to variations. Real-time quantitative PCR could be a valid alternative. A TaqMan probe was designed to hybridize with the NeoR gene. The PCR product is 64 nucleotides long and readily quantified by TaqMan probe binding. The analysis was performed soon after transduction and repeated after the selection procedure. This method was more accurate, reproducible, and sensitive than the semiquantitative PCR assay. Accuracy was the same whether the analysis was performed at the highest rate or at the lowest rate of transduction. Additionally we used real-time PCR to monitor the kinetics of enrichment of the transduced cells over the selection time and showed how 7 days of selection are needed. This study precisely quantified the percentages of cells transduced by the retroviral vector and could have major implications in gene therapy studies.

Toxic epidermal necrolysis in a patient with primary myelofibrosis receiving thalidomide therapy

Primary myelofibrosis (PMF) is a chronic myeloproliferative neoplasm characterized by progressive anemia, massive splenomegaly, leukoerythroblastosis, extramedullary hematopoiesis and in about 50% of cases the presence of JAK2V617F mutation. Curative therapy in PMF is currently possible only with allogeneic haematopoietic stem cell transplantation which is, unfortunately, associated with relatively high risks of mortality and morbidity which undermine its broad applications. Non-transplant treatment modalities are used for palliative purposes. Recently, anti-angiogenic drugs such as thalidomide have been used to treat these patients on the basis of the prominent bone marrow angiogenesis. Here, we report the case of a patient suffering from JAK2V617F-positive PMF with marked bone marrow neo-angiogenesis. The patient was treated with thalidomide but after 20 days developed life-threatening toxic epidermal necrolysis (TEN). To the best of our knowledge this is the first case of TEN in a patient with PMF under thalidomide therapy.

Unique human CD133+ leukemia cell line and its modulation towards a mesenchymal phenotype by FGF2 and TGFβ1†

Immunological features of GM‐490 cells, a new blood cell line from a patient with acute lymphoblastic leukemia, included lack of CD34, CD38, CD45, CD14, HLA‐DR, and lymphoid and myeloid markers and expression of CD29, CD36, CD44, CD54, CD71, CD105, and CD133. Molecular analysis indicated CD45 gene expression was absent but CD34 mRNA was present. GM‐490 cells constitutively produced fibronectin (FN), type III and traces of type I collagen, collagenases, glycosaminoglycans (GAG) and biglycan and betaglycan proteoglycans (PG) as well as FGF2 and TGFβ1. When FGF2 and/or TGFβ1 were added to cells in vitro, they stimulated cell proliferation and differently modulated matrix production and growth factor receptor expression. Reverse transcription‐polymerase chain reaction (RT‐PCR) detection of transcripts encoding for osteocalcin and RUNX2 suggests GM‐490 cells differentiate towards the osteoblast pathway. GM‐490 cells expressed the low affinity nerve growth factor receptor (p75LNGFR), a somatic stem cell marker that is not detected in hematopoietic cells, leading to the hypothesis that GM‐490 has mesenchymal stem cell properties. The reciprocal modulating effects of FGF2 and TGFβ1 on each others receptors make the GM‐490 cell line a new model for investigating the relationship between these growth factors and their receptors in autocrine loops which are believed to sustain the malignant clone in hematological diseases.

Chronic myeloproliferative disorders: the bone marrow stromal component is not involved in the malignant clone

Chronic myeloproliferative disorders: the bone marrow stromal component is not involved in the malignant clone

Activated autologous T cells exert an anti-B-cell chronic lymphatic leukemia effect in vitro and in vivo

BACKGROUND AIMS The impact of chronic lymphatic leukemia (CLL) tumor burden on the autologous immune system has already been demonstrated. This study attempted to elucidate the molecular mechanisms underlying T-cell immunologic deficiencies in CLL. METHODS Freshly isolated CD3(+) T cells from patients with a diagnosis of CLL and healthy donors were analyzed by gene expression profiling. Activated T cells from 20 patients with CLL were tested in vitro for cytotoxicity against mutated and unmutated autologous B cells and DAUDI, K562 and P815 cell lines. To investigate T-cell mediated cytotoxicity in vivo, we co-transplanted OKT3-activated T lymphocytes and autologous B-cell CLL (B-CLL) cells into NOD/SCID mice. RESULTS Gene expression profiles of peripheral blood T cells from B-CLL patients showed 25 down-regulated, and 31 up-regulated, genes that were mainly involved in cell differentiation, proliferation, survival, apoptosis, cytoskeleton formation, vesicle trafficking and T-cell activation. After culture, the T-cell count remained unchanged, CD8 cells expanded more than CD4 and a cytotoxicity index >30% was present in 5/20 patients. Cytotoxicity against B autologous leukemic cells did not correlate with B-cell mutational status. Only activated T cells exerting cytotoxicity against autologous leukemic B cells prevented CLL in a human-mouse chimera. CONCLUSIONS This study indicates that patients with CLL are affected by a partial immunologic defect that might be somewhat susceptible to repair. This study identifies the molecular pathways underlying T-cell deficiencies in CLL and shows that cytotoxic T-cell functions against autologous B-CLL can be rebuilt at least in part in vitro and in vivo.