Studies on monozygotic twins with concordant leukemia and retrospective scrutiny of neonatal blood spots of patients with leukemia indicate that chromosomal translocations characteristic of pediatric leukemia often arise prenatally, probably as initiating events. The modest concordance rate for leukemia in identical twins (Ϸ5%), protracted latency, and transgenic modeling all suggest that additional postnatal exposure and͞or genetic events are required for clinically overt leukemia development. This notion leads to the prediction that chromosome translocations, functional fusion genes, and preleukemic clones should be present in the blood of healthy newborns at a rate that is significantly greater than the cumulative risk of the corresponding leukemia. Using parallel reverse transcriptase-PCR and real-time PCR (Taqman) screening, we find that the common leukemia fusion genes, TEL-AML1 or AML1-ETO, are present in cord bloods at a frequency that is 100-fold greater than the risk of the corresponding leukemia. Single-cell analysis by cell enrichment and immunophenotype͞ fluorescence in situ hybridization multicolor staining confirmed the presence of translocations in restricted cell types corresponding to the B lymphoid or myeloid lineage of the leukemias that normally harbor these fusion genes. The frequency of positive cells (10 ؊4 to 10 ؊3 ) indicates substantial clonal expansion of a progenitor population. These data have significant implications for the pathogenesis, natural history, and etiology of childhood leukemia.C himeric fusion genes generated by chromosomal translocations are consistent genetic abnormalities in pediatric acute leukemia (1-3). DNA breaks and fusions occur in introns, and each patient's leukemic cells have a unique or clonotypic breakpoint, providing a specific, sensitive, and stable marker for tracking leukemic clones (4). Using this approach in identical twins with concordant leukemia (5-7) and, retrospectively, with neonatal blood spots (8-10), it was demonstrated that common fusion genes-MLL fusions in infants with acute lymphoblastic leukemia (ALL) and TEL-AML1 and AML1-ETO in children with ALL or acute myeloblastic leukaemia (AML), respectively-arise predominantly in utero, probably as initiating events, and are present before and at birth in circulating blood.The evolutionary, clonal development of pediatric cancers involves a sequence of two or more independent genetic events (11), and it therefore is unlikely that fusion genes, initiating the disease, would be sufficient. This supposition is supported by the modest concordance rate for ALL in monozygotic twin children, 5-10% (12), by protracted postnatal latency (up to 14 years) (7) and by the absence of overt signs of leukemia in mice transgenic for AML1-ETO (13) or TEL-AML1 (14). This finding leads to the prediction that chromosomal translocations, functional fusion genes, and preleukemic clones should be generated in stem cells during fetal hemopoiesis, and present in blood at birth, at a rate that substantially exceeds the k...

The risk of highly likely/probable TRALI due to FFP has fallen from 15.5 per million units issued during 1999 through 2004 to 3.2 per million during 2005 through 2006 (p = 0.0079) and from 14.0 per million to 5.8 per million for PLTs.

SummaryPlatelet refractoriness can represent a significant clinical problem that complicates the provision of platelet transfusions, is associated with adverse clinical outcomes and increases health care costs. Although it is most frequently due to non-immune platelet consumption, immunological factors are also often involved. Human leucocyte antigen (HLA) alloimmunization is the most important immune cause. Despite the fact that systematic reviews of the clinical studies evaluating different techniques for selecting HLA compatible platelets have not been powered to demonstrate improved clinical outcomes, platelet refractoriness is currently managed by the provision of HLA-matched or cross matched platelets. This review will address a practical approach to the diagnosis and management of platelet refractoriness while highlighting on-going dilemmas and knowledge gaps.

Donor killer cell immunoglobulin-like receptor (KIR)-ligand incompatibility is associated with decreased relapse incidence (RI) and improved leukemia-free survival (LFS) after haploidentical and HLA-mismatched unrelated hematopoietic stem cell transplantation. We assessed outcomes of 218 patients with acute myeloid leukemia (AML n ¼ 94) or acute lymphoblastic leukemia (n ¼ 124) in complete remission (CR) who had received a single-unit unrelated cord blood transplant (UCBT) from a KIR-ligand-compatible or -incompatible donor. Grafts were HLA-A, -B or -DRB1 matched (n ¼ 21) or mismatched (n ¼ 197). Patients and donors were categorized according to their degree of KIR-ligand compatibility in the graft-versus-host direction by determining whether or not they expressed HLA-C group 1 or 2, HLA-Bw4 or HLA-A3/-A11. Both HLA-C/-B KIR-ligand-and HLA-A-A3/-A11 KIR-ligand-incompatible UCBT showed a trend to improved LFS (P ¼ 0.09 and P ¼ 0.13, respectively). Sixty-nine donor-patient pairs were HLA-A, -B or -C KIR-ligand incompatible and 149 compatible. KIR-ligandincompatible UCBT showed improved LFS (hazards ratio ¼ 2.05, P ¼ 0.0016) and overall survival (OS) (hazards ratio ¼ 2.0, P ¼ 0.004) and decreased RI (hazards ratio ¼ 0.53, P ¼ 0.05). These results were more evident for AML transplant recipients (2-year LFS and RI with or without KIR-ligand incompatibility 73 versus 38% (P ¼ 0.012), and 5 versus 36% (P ¼ 0.005), respectively). UCBT for acute leukemia in CR from KIR-ligandincompatible donors is associated with decreased RI and improved LFS and OS.

Background and ObjectivesMesenchymal stem/progenitor cells (MSCs) are multipotent progenitors that differentiate into such lineages as bone, fat, cartilage and stromal cells that support haemopoiesis. Bone marrow MSCs can also contribute to cardiac repair, although the mechanism for this is unclear. Here, we examine the potential of MSCs from different sources to generate cardiomyocytes in vitro , as a means for predicting their therapeutic potential after myocardial infarction. Materials and MethodsMesenchymal stem/progenitor cells were isolated from the perivascular tissue and Wharton's jelly of the umbilical cord and from cord blood. Their immunophenotype and differentiation potential to generate osteoblasts, chondrocytes, adipocytes and cardiomyoxcytes in vitro was compared with those of bone marrow MSCs.Results Mesenchymal stem/progenitor cells isolated from umbilical cord and cord blood were phenotypically similar to bone marrow MSCs, the exception being in the expression of CD106, which was absent on umbilical cord MSCs, and CD146 that was highly expressed in cord blood MSCs. They have variable abilities to give rise to osteoblasts, chondrocytes and adipocytes, with bone marrow MSCs being the most robust. While a small proportion (~0·07%) of bone marrow MSCs could generate cardiomyocyte-like cells in vitro, those from umbilical cord and cord blood did not express cardiac markers either spontaneously or after treatment with 5-azacytidine. ConclusionAlthough MSCs may be useful for such clinical applications as bone or cartilage repair, the results presented here indicate that such cells do not generate cardiomyocytes frequently enough for cardiac repair. Their efficacy in heart repair is likely to be due to paracrine mechanisms.

Mesenchymal stromal cells (MSCs) may be derived from a variety of tissues, with human umbilical cord (UC) providing an abundant and noninvasive source. Human UC-MSCs share similar in vitro immunosuppressive properties as MSCs obtained from bone marrow and cord blood. However, the mechanisms and cellular interactions used by MSCs to control immune responses remain to be fully elucidated. In this paper, we report that suppression of mitogen-induced T cell proliferation by human UC-, bone marrow-, and cord blood-MSCs required monocytes. Removal of monocytes but not B cells from human adult PBMCs (PBMNCs) reduced the immunosuppressive effects of MSCs on T cell proliferation. There was rapid modulation of a number of cell surface molecules on monocytes when PBMCs or alloantigen-activated PBMNCs were cultured with UC-MSCs. Indomethacin treatment significantly inhibited the ability of UC-MSCs to suppress T cell proliferation, indicating an important role for PGE2. Monocytes purified from UC-MSC coculture had significantly reduced accessory cell and allostimulatory function when tested in subsequent T cell proliferation assays, an effect mediated in part by UC-MSC PGE2 production and enhanced by PBMNC alloactivation. Therefore, we identify monocytes as an essential intermediary through which UC-MSCs mediate their suppressive effects on T cell proliferation.

Summary:blood, but their numbers can be dramatically, albeit transiently, increased following treatment with conventional chemotherapy and administration of haemopoietic growth An essential prerequisite for successful procurement of sufficient autologous peripheral blood progenitor cells factors such as granulocyte colony-stimulating factor (G-CSF). 4,5 After mobilisation the PBPC are removed from the (PBPC) for engraftment is the optimal timing of collection. A number of surrogate markers of peripheral patient's circulation by apheresis and the adequacy of the collection is assessed by the product's content of nucleated blood progenitor cells were analysed to identify a single test which could predict the optimum time to harvest, cells, mononuclear cells, granulocyte-macrophage colonyforming units (CFU-GM) or CD34 + cells. providing at least 2 × 10 6 CD34 + cells/kg patient body weight. The study comprised 95 patients undergoingThere is a tremendous variation in the yield of haemopoietic progenitor cells obtained from patients following varied mobilisation regimens with chemotherapy and G-CSF for both solid tumours and haematological mobilisation which results in some patients requiring only one leucapheresis whereas others require two, three or even malignancies. One hundred and fifty-seven PBPC harvests were collected. Full blood counts (FBC) and four procedures. A number of different protocols are used to mobilise PBPC and the decision as to when to commence CD34 ؉ cell enumeration was performed on blood samples taken during the mobilisation period and the apheresis procedure is generally based on the patient's white cell count (WCC). Obviously the successful procureimmediately prior to leucapheresis (pre-harvest). All PBPC collections were assayed for colony-forming cells ment of sufficient PBPC to ensure haemopoietic engraftment is essential. To ensure that this goal is achiand CD34 ؉ cells in addition to a FBC. The white cell count on the day of harvest showed only weak correeved, with the least number of leucapheresis procedures, the optimal time for collection must be predicted as acculation with the total number of CD34 ؉ cells in the collection (r = 0.30). In contrast, the absolute number of circurately as possible. This is not only advantageous for the patient but also for both operational and financial lating CD34 + cells strongly correlated with the CD34 ؉ cell and CFU-GM yield of the corresponding apheresis efficiency. This study involved the analysis of the WCC, monoproduct. Provided the mobilisation sample contained у20 × 10 6 CD34 ؉ cells/ml, 94% of single collections, nuclear cell count (MNC), CD34 + cells and colony-forming units (CFU) on samples obtained from 95 patients with both performed the following day, contained у2 × 10 6

The immunosuppressive properties of mesenchymal stem cells (MSC) make them particularly attractive to manipulate graftversus-host disease (GVHD). So far, the experience of using MSC to treat GVHD is limited to a few cases, controversial results come from preclinical models and several issues remain to be clarified. The present studies were designed to address these questions in a xenogenic model testing the ability of umbilical cord blood-derived MSC (UCB-MSC) to prevent and/or treat GVHD. Sublethally irradiatiated non-obese diabetic/severe combined immunodeficiency NOD/SCID mice transplanted with human peripheral blood mononuclear cells (huPBMC) showed extensive human T-cell proliferation in the peripheral blood, lymphoid and non-lymphoid tissues, which evolved in extensive GVHD (wasting, ruffled hair and hunched back). The mice treated with a single dose of UCB-MSC did not behave differently form the controls. However, when UCB-MSC were given at weekly intervals, there was a marked decrease in human T-cell proliferation and none of the mice developed GVHD. No therapeutic effect was obtained if UCB-MSC were administered at onset of GVHD. This work supports the clinical use of MSC in stem cell transplantation as a prophylaxis rather than treatment of GVHD.