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A two-step separation procedure is described for the positive selection of cells based on their reactivity with mouse monoclonal antibodies. In the first step cells are specifically cross-linked to hapten-modified glass beads using tetrameric monoclonal antibody complexes. In the second step bound cells are selectively eluted by reductive cleavage of the tetrameric antibody complexes. The latter are comprised of two mouse IgG1 monoclonal antibodies (one recognizing a cell surface antigen on target cells and the other a hapten coupled to the glass beads) bound together by two F(ab')2 fragments of rat anti-mouse IgG1 monoclonal antibody. The complexes provide a specific cleavable cross-link between cell and bead because the disulfide bonds between the two Fab' arms of the F(ab')2 fragments can be broken under relatively mild conditions using dithiothreitol. This specific cleavage of the cross-linker allows elution of the specifically absorbed cells without co-elution of non-specifically bound cells. This is shown in the purification of CD3+ T cells from human peripheral blood,where the removed fractions were over 90% pure and approximately 50% of the positive cells were recovered. Separation of cells labelled with limiting amounts of tetrameric antibody complexes demonstrated that this separation technique was also effective for the purification of cells expressing low amounts of antigens. This was confirmed by the purification of CD34-positive cells from human bone marrow. With this approach,colony-forming cells were enriched 15-24-fold over density separated marrow. View Publication

The exchange of ribosomal subunits during the release of growing polypeptide chains by puromycin has been investigated in a bacterial cell-free system engaged in protein synthesis. The addition of spermidine,used as a stabilizing agent of 70S monomers,caused a strong inhibition of the subunit exchange. This result led us to conclude that upon premature release of unfinished protein chains by the antibiotic,the ribosomes fall off mRNA as 70S particles. This behavior is different from that occurring during physiological termination of translation,where the ribosomes detach in a dissociated form. Some implications of the postulated mechanism are also discussed. View Publication

Squalene-based emulsion (SE) adjuvants like MF59 and AS03 are used in protein subunit vaccines against influenza virus (e.g.,Fluad,Pandemrix,Arepanrix) and SARS-CoV-2 (e.g.,Covifenz,SKYCovione). We demonstrate the critical role of uric acid (UA),a damage-associated molecular pattern (DAMP),in triggering immunogenicity by SE adjuvants. In mice,SE adjuvants elevated DAMP levels in draining lymph nodes. Strikingly,inhibition of UA synthesis reduced vaccine-induced innate immunity,subsequently impairing optimal antibody and T cell responses. In vivo treatment with UA crystals elicited partial adjuvant effects. In vitro stimulation with UA crystals augmented the activation of dendritic cells (DCs) and B cells and altered multiple pathways in these cells,including inflammation and antigen presentation in DCs and cell proliferation in B cells. In an influenza vaccine model,UA contributed to protection against influenza viral infection. These results demonstrate the importance of DAMPs,specifically the versatile role of UA in the immunogenicity of SE adjuvants,by regulating DCs and B cells. View Publication

BACKGROUND AND OBJECTIVES: Interactions between acute myelogenous leukemia (AML) blasts and non-leukemic cells in the bone marrow seem to be important for both disease development and susceptibility to chemotherapy. Recent studies have focused on the endothelial cells,but other non-leukemic cells may also be involved. In the present study we investigated how osteoblasts affect native human AML blasts. DESIGN AND METHODS: AML cells were derived from a large group of consecutive patients. The AML blasts and osteoblastic sarcoma cell lines (Cal72,SJSA-1) were incubated together in different chambers separated by a semipermeable membrane. We investigated effects of co-culture on proliferation,apoptosis and cytokine release. RESULTS: The cross-talk between these two cell populations,achieved via release of soluble mediators,resulted in increased AML blast proliferation,including increased proliferation of clonogenic progenitors,but did not affect spontaneous in vitro apoptosis. Both interleukin (IL) 1-b and granulocyte-macrophage colony-stimulating factor were involved in this growth-enhancing cross-talk,and normal osteoblasts could also increase the AML blast proliferation. Furthermore,co-culture of AML blasts with osteoblastic sarcoma cells as well as normal osteoblasts increased the levels of the pro-angiogenic mediator IL8. INTERPRETATION AND CONCLUSIONS: Our in vitro results suggest that the release of soluble mediators by osteoblasts supports leukemic hematopoiesis through two major mechanisms: (i) direct enhancement of AML blast proliferation; and (ii) enhanced angiogenesis caused by increased IL8 levels. View Publication

We examined the potential role of myosin and actin in the release of human immunodeficiency virus type 1 (HIV-1) from infected cells. Wortmannin (100 nM to 5 microM),an effective inhibitor of myosin light chain kinase,blocked the release of HIV-1 from infected T-lymphoblastoid and monocytoid cells in a concentration-dependent manner. Cytochalasin D,a reagent that disrupts the equilibrium between monomeric and polymeric actin,also partially inhibited the release of HIV-1 from the infected cells. At the budding stage,myosin and HIV-1 protein were detected in the same areas on the plasma membrane by using dual-label immunofluorescence microscopy and immunoelectron microscopy. In the presence of 5 microM wortmannin,viral components were observed on the plasma membrane by using immunofluorescence microscopy and electron microscopy,implying that wortmannin did not disturb the transport of viral proteins to the plasma membrane but rather inhibited budding. View Publication

BackgroundActivated fibroblast-like synoviocytes (FLS) are drivers of synovitis and structural joint damage in rheumatoid arthritis (RA). Despite the use of disease-modifying drugs,only about 50% of RA patients reach remission in real-world settings. We used an unbiased approach to investigate the effects of standard-of-care methotrexate (MTX) and a Janus kinase inhibitor,tofacitinib (TOFA),on gene expression in RA-FLS,in order to identify untargeted disease mediators.MethodsPrimary RA-FLS were activated by stimulation with interleukin-1β (IL-1β) or platelet-derived growth factor + IL-1β in the presence or absence of MTX or TOFA,with or without additional inhibitors. Co-cultures of synovial cells were performed in direct and indirect systems. Cells were collected for RNA sequencing or qPCR,and supernatants were analyzed for protein concentrations.ResultsSix thousand three hundred fifty genes were differentially expressed,the majority being upregulated,in MTX-treated activated RA-FLS and 970 genes,the majority being downregulated,in TOFA-treated samples. Pathway analysis showed that MTX had largest effects on ‘Molecular mechanisms of cancer’ and TOFA on ‘Interferon signaling’. Targeted analysis of disease-associated genes revealed that MTX increased the expression of cell cycle-regulating genes but also of pro-inflammatory mediators like IL-1α (IL1A) and granulocyte–macrophage colony-stimulating factor,GM-CSF (CSF2). The MTX-promoted expression of CSF2 in activated RA-FLS peaked at 48 h,could be mediated via either NF-κB or AP-1 transcription factors,and was abrogated by IL-1 inhibitors (IRAK4 inhibitor and anakinra). In a co-culture setting,MTX-treatment of activated RA-FLS induced IL1B expression in macrophages.ConclusionsMTX treatment induces secretion of IL-1 from activated RA-FLS which by autocrine signaling augments their release of GM-CSF. This unexpected effect of MTX might contribute to the persistence of synovitis. View Publication

HIV-1 infection leads to numerous B cell abnormalities,including hypergammaglobulinemia,nonspecific B cell activation,nonspecific class switching,increased cell turnover,breakage of tolerance,increased immature/transitional B cells,B cell malignancies,as well as a loss of capacity to generate and maintain memory,all of which contribute to a global impairment of the immune humoral compartment. Several cytokines and soluble factors,which are increased in sera of HIV-1-infected individuals,have been suggested to directly or indirectly contribute to these B cell dysfunctions,and one of these is the B cell-activating factor (BAFF). We report in this study that HIV-1 (X4- and R5-tropic) upregulates BAFF expression and secretion by human monocytes. Moreover,we show that the virus-mediated production of BAFF by monocytes relies on a type I IFN response by a small percentage of plasmacytoid dendritic cells (pDCs) present in the monocyte cultures. HIV-1-induced type I IFN by pDCs triggers BAFF production in both classical and intermediate monocytes,but not in nonclassical monocytes,which nonetheless display a very strong basal BAFF production. We report also that basal BAFF secretion was higher in monocytes obtained from females compared with those from male donors. This study provides a novel mechanistic explanation for the increased BAFF levels observed during HIV-1 infection and highlights the importance of pDC/monocyte crosstalk to drive BAFF secretion. View Publication