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Recent studies have shown that human myeloid leukaemia cells can differentiate into dendritic cell (DC)-like cells (leukaemia-DCs) when cultured with a combination of cytokines. In the present study, we examined whether the transduction of leukaemia-DCs with OX40 ligand (OX40L), a member of the tumour necrosis factor (TNF) family, resulted in augmentation of their antigen presenting activity. Bicistronic retroviral vectors expressing both human OX40L and enhanced green fluorescent protein (EGFP) or EGFP alone were generated and used for transduction. Fresh leukaemic cells from five patients with acute myeloid leukaemia (AML) were isolated and retrovirally transduced with OX40L during the culture with a combination of cytokines from stem cell factor, fms-like tyrosine kinase (Flt)-3 ligand, granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin-4 (IL-4) and TNF- α. After 7 d, the majority of cells showed DC-like morphology, and expressed higher levels of CD80, CD86 and HLA-DR than fresh leukaemic cells. The transduction efficiency was 8·5–27·2%. Leukaemia-DCs transduced with OX40L elicited higher proliferative response of allogeneic CD4+ T cells than fresh leukaemic cells, non-transduced, or mock-transduced leukaemia-DCs. Co-culture of allogeneic CD4+ T cells with OX40L-transduced leukaemia-DCs was superior in the generation of interferon (IFN)- γ producing CD4+ T cells and in production of IFN- γ. Furthermore, OX40L-transduced leukaemia-DCs could elicit significant proliferative response of human leucocyte antigen-matched T cells from the donor in allogeneic stem cell transplantation. These results indicate that retroviral transduction of leukaemia-DCs with OX40L augments their antigen presenting cell activity and thus renders them more suitable for tumour vaccines or ex vivo stimulation of leukaemia-specific T cells. [ABSTRACT FROM AUTHOR]

In a companion article to this study,1 the successful programming of a JAWSII dendritic cell ( DC) line's antigen uptake and processing was demonstrated based on pre-treatment of DCs with a specific 'cocktail' of select chemokines. Chemokine pre-treatment modulated cytokine production before and after DC maturation [by lipopolysaccharide (LPS)]. After DC maturation, it induced an antigen uptake and processing capacity at levels 36% and 82% higher than in immature DCs, respectively. Such programming proffers a potential new approach to enhance vaccine efficiency. Unfortunately, simply enhancing antigen uptake does not guarantee the desired activation and proliferation of lymphocytes, e.g. CD4+ T cells. In this study, phenotype changes and antigen presentation capacity of chemokine pre-treated murine bone marrow-derived DCs were examined in long-term co-culture with antigen-specific CD4+ T cells to quantify how chemokine pre-treatment may impact the adaptive immune response. When a model antigen, ovalbumin ( OVA), was added after intentional LPS maturation of chemokine-treated DCs, OVA-biased CD4+ T-cell proliferation was initiated from ~ 100% more undivided naive T cells as compared to DCs treated only with LPS. Secretion of the cytokines interferon-γ, interleukin-1β, interleukin-2 and interleukin-10 in the CD4+ T cell : DC co-culture (with or without chemokine pre-treatment) were essentially the same. Chemokine programming of DCs with a 7 : 3 ratio of CCL3 : CCL19 followed by LPS treatment maintained partial immature phenotypes of DCs, as indicated by surface marker ( CD80 and CD86) expression over time. Results here and in our companion paper suggest that chemokine programming of DCs may provide a novel immunotherapy strategy to obviate the natural endocytosis limit of DC antigen uptake, thus potentially increasing DC-based vaccine efficiency. [ABSTRACT FROM AUTHOR]

By substituting the heavy chain constant region of IgM and IgD with that of IgG, IgA or IgE, immunoglobulin class switching endows antibodies with novel effector functions that enhance the ability of the immune system to effectively clear invading pathogens. Plasmacytoid dendritic cells critically link innate immunity with adaptive immunity by producing massive amounts of type 1 IFN in response to viruses. We have recently found that type 1 IFN triggers class switching by inducing myeloid dendritic cells to upregulate the expression of BAFF and APRIL, two powerful B cell-activating molecules. In this paper, we propose that IFN-producing plasmacytoid dendritic cells modulate class switching by activating B cells through both T cell-dependent and T cell-independent pathways. A better understanding of these pathways may facilitate the development of novel antiviral vaccine strategies and aid in identifying new therapies for antibody-mediated autoimmune disorders, such as lupus. [ABSTRACT FROM AUTHOR]

During the last decade use of dendritic cells (DC) has moved from murine and in vitro studies to clinical trials as adjuvant in cancer immunotherapy. Here they function as delivery vehicles for exogenous tumor antigens, promoting an efficient antigen presentation. The development of protocols for large-scale generation of dendritic cells for clinical applications has made possible phase I/II studies designed to analyze the toxicity, feasibility and efficacy of this approach. In clinical trials, DC-based vaccination of patients with advanced cancer has in many cases led to immunity and in selected patients to tumor regression. However, the majority of clinical trials are still in phase I, and interpretations are hampered by pronounced variation in study design related to technical aspects of DC preparation, treatment and schedule, monitoring of immune response, and clinically relevant endpoints, including toxicity and response evaluation. This paper aims to review the technical aspects and clinical impact of vaccination trials, focusing on the generation of DC-based vaccines, evaluation of immunologic parameters and design of clinical trials necessary to meet the need for good laboratory and clinical practice. [ABSTRACT FROM AUTHOR]