Granulocyte-macrophage colony-stimulating factor, interleukin-2, and interleukin-12 synergize with calcium ionophore to enhance dendritic cell function

The authors previously showed that monocytes treated with calcium ionophore (CI) acquire characteristics of mature dendritic cells (DC) in part through a calcineurin-dependent pathway. In this study, the authors evaluated the ability of granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin-2 (IL-2), and interleukin-12 (IL-12) alone or in combination with CI to induce DC characteristics in peripheral blood monocytes. Monocytes obtained by leukapheresis and countercurrent centrifugal elutriation were cultured with calcium, cytokines, or both, profiled by flow cytometry, and assessed for antigen uptake and sensitization of autologous CD8+ T cells to antigen. Monocytes treated with the combination of GM-CSF, IL-2, and IL-12 resulted in immunophenotypic and antigen uptake profiles typical of immature DC, including loss of surface CD14 expression, de novo low-level expression of B7.1, negligible CD83 expression, marked enhancement of CD40 and ICAM-1, and high major histocompatibility complex class I and II levels. A high level of antigen uptake by macro-pinocytosis was observed. In contrast, CI treatment significantly up-regulates B7.1, B7.2, CD40, CD54, and CD83 and substantially down-regulates CD14 and macro-pinocytosis, a profile consistent with mature DC. Many CI-induced modulations, but none resulting from cytokine treatment alone, were inhibited by the calcineurin phosphatase inhibitor cyclosporin A. Compared with monocytes treated with CI alone, combined treatment of monocytes with GM-CSF, IL-2, IL-12, and CI augmented B7.1 and CD83 expression and enhanced sensitization of autologous CD8+ T cells to melanoma-antigen-derived peptides. These results suggest that several independent pathways of DC activation can cooperatively enhance the function of monocyte-derived DC.     

Uncoordinated expression of fibrinogen compared with thrombospondin and von Willebrand factor in maturing human megakaryocytes

The localization of three known alpha-granule proteins, thrombospondin (TSP), von Willebrand factor (vWF), and fibrinogen (Fg) has been studied in human megakaryocytes (MK) by immunofluorescence and immunoelectron microscopy. For this study, highly purified populations of MK were prepared from human bone marrow either by counterflow centrifugal elutriation or by cell culture from normal subjects and from two patients with megakaryoblastic leukemia. In normal bone marrow immature MK, TSP, and vWF were observed in the Golgi-associated vesicles and in small immature alpha-granules; in mature MK, they were found in the matrix of the mature large alpha-granules. Surprisingly, Fg was detected neither in the Golgi area, nor in the small precursors of alpha-granules; it was only found in the mature alpha-granules but this labeling was generally weaker than in blood platelets. In order to confirm these differences between the expression of Fg and vWF or TSP additional studies were performed on cultured maturing MK: immunofluorescent and ultrastructural immunogold labeling confirmed that vWF appeared early in the maturation while the same immature MK were negative for Fg. In the late maturation stage, the three proteins were detected in the alpha-granules. In order to know whether Fg was lately synthesized or endocytosed from the outside medium, normal MK were grown in the presence of either normal or afibrinogenemic plasma, and normal serum. Fg was detected only in the alpha-granules of MK grown in normal plasma. Similar results were observed with malignant MK, whose maturation was independent of the culture conditions. In conclusion, this study brings immunocytochemical evidence that vWF and TSP are synthesized by immature MK, whereas Fg appears later in the MK alpha-granules and its expression is dependent of the presence of an exogenous Fg source.     

Extended long-term culture reveals a highly quiescent and primitive human hematopoietic progenitor population

Long-term culture-initiating cells (LTC-IC) are hematopoietic progenitors able to generate colony-forming unit-cells (CFU) after 5 to 8 weeks (35 to 60 days) of culture on bone marrow (BM) stroma and represent the most primitive progenitors currently detectable in vitro. We have recently reported that long-term cultures initiated with CD34+CD38- cells from BM or cord blood are able to continue generating CFU for at least 100 days, ie, beyond the standard LTC-IC period. In this report, single-cell cultures from cord blood and retroviral marking of cord blood and BM were used to study whether the subpopulation of CD34+CD38- cells able to generate CFU beyond 60 days ("extended long-term culture-initiating cells" or ELTC-IC) are functionally distinct from LTC-IC in terms of timing of initial clonal proliferation and generative capacity. All cord blood LTC-IC formed clones of greater than 50 cells by day 30. In contrast, cord blood ELTC- IC proliferated later in culture, 50% forming clones after day 30. Although efficient retroviral marking of LTC-IC was seen (25% to 45%), marking of ELTC-IC was inefficient (< 1%), consistent with a more quiescent progenitor population. There was a positive correlation between time of clonal proliferation and generative capacity. ELTC-IC generated threefold to fourfold more progeny than did LTC-IC (P < .002). These studies show that there is a functional hierarchy of progenitors in long-term culture which correlates with their level of quiescence. By extending the LTC-IC assay, a more primitive progenitor may be studied that may be functionally closer to the human long-term repopulation stem cell in vivo.     

The 2013 Model of the Clinical Practice of Emergency Medicine

In 2001, “The Model of the Clinical Practice of Emergency Medicine” was first published. This document, the first of its kind, was the result of an extensive practice analysis of emergency department (ED) visits and several expert panels, overseen by representatives from six collaborating professional organizations (the American Board of Emergency Medicine, the American College of Emergency Physicians, the Society for Academic Emergency Medicine, the Residency Review Committee for Emergency Medicine, the Council of Emergency Medicine Residency Directors, and the Emergency Medicine Residents' Association). Every 2 years, the document is reviewed by these organizations to identify practice changes, incorporate new evidence, and identify perceived deficiencies. For this revision, a seventh organization was included, the American Academy of Emergency Medicine.     

Systemic lupus erythematosus, thrombocytopenia, microangiopathic haemolytic anaemia and anti-CD36 antibodies [clinical conference]

Thrombocytopenia in patients with acute systemic lupus erythematosus (SLE) frequently presents the clinician with considerable diagnostic and therapeutic difficulties. In this Grand Round, we present a 48-yr- old woman with a 7 yr history of lupus, who presented with acute proliferative glomerulonephritis and nephrotic syndrome, pneumonia, profound hypocomplementaemia and a severe microangiopathic haemolytic anaemia with associated thrombocytopenia. Her thrombocytopenia proved initially refractory to conventional immunosuppressive therapy, and corticosteroids, and resolved only with plasma exchange and repeated fresh frozen plasma infusions. Serological testing revealed high-titre antinuclear antibodies (ANA) and markedly raised antibodies to double- stranded (ds) DNA, but no significant elevation in anticardiolipin antibodies. Platelet-associated IgG and IgM and antibodies to the CD36 glycoprotein antigen, expressed on platelets and endothelium, were detected in the serum. We address some of the difficult diagnostic and management issues raised by this complex patient and the possible immunopathological links between antibodies to CD36, immune-mediated red cell destruction, thrombocytopenia and thrombotic microangiopathic haemolytic anaemia.      

Partial plasma exchange using albumin replacement: removal and recovery of normal plasma constituents

Using albumin and crystalloid as the only replacement fluids, the effect of partial plasma exchange on the removal and recovery of normal plasma constituents was studied. The results of 30 procedures on 10 individuals were evaluated. Four patterns of removal are described: reduction in the concentration of fibrinogen and C3 were greater than would be expected based upon the extent of the exchange, while IgG, IgM, cholesterol, alkaline phosphatase and SGPT were removed as expected. Reduction of serum glutamicoxalacetic transaminase (SGOT), lactate dehydrogenase (LDH), amylase, and creatine phosphokinase (CPK) averaged 17% less, and uric acid, calcium and K+ averaged 53% less than expected. Concentrations of HCO-3 and glucose did not change. The mean recovery for all constituents except fibrinogen, C3, cholesterol. IgG and IgM was near 100% at 48-72 hr postpheresis. The 72-hr recovery of fibrinogen and complement was 66% and 60%, respectively. Cholesterol recovery was also slow, requiring a minimum of 1 wk to reach prepheresis levels. Measured at a time when quantitative IgM levels were still reduced, alloantibody agglutinating activity (anti-A and anti-B) in a postpheresis sample exceeded prepheresis agglutinating activity. These data demonstrated that, depending upon quantity and frequency of pheresis, partial plasma exchange using albumin replacement may cause progressive marked reduction in concentrations of immunoglobulin, complement, fibrinogen, and cholesterol. Furthermore, newly synthesized antibody may have increased biologic activity.