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Multiple myeloma (MM) cells express certain tumour-associated antigens (TAAs) that could serve as targets for active-specific immunotherapy. The aim of the present study was to test the MM/dendritic cell (DC) fusion as a vaccination strategy. We fused MM cells with DC to generate fusion cells (FCs) and tested their antigen presenting cell (APC) function in mixed lymphocyte reactions and cytotoxicity assays. First, the HS Sultan and SK0-007 HAT sensitive human MM cell lines and DCs generated from peripheral blood of normal donors were fused in the presence of 50% polyethylene glycol to form FCs. Next, tumour cells freshly isolated from patients were similarly fused with autologous DCs to generate FCs. The FCs demonstrated a biphenotypic profile, confirmed both by flow-cytometry and dual immunofluorescence microscopy. These FCs induced MM-specific cytotoxicity. FCs, but not MM cells or DCs alone, were potent stimulators of autologous patient T cells. More importantly, FC-primed autologous peripheral blood mononuclear cells demonstrated major histocompatibility complex-restricted MM-specific cytolysis. These studies therefore demonstrated that MM/DC FC can trigger an autologous immune response to MM cells and formed the framework for a clinical trial currently underway. [ABSTRACT FROM AUTHOR]

The article presents a list of articles related to immunology. The articles include "Monocyte-Derived Dendritic Cells From Horses Differ From DC of Humans and Mice," by Susanne Mauel, Falko Steinbach and Hanns Ludwig, "Extended Sequence Preferences for Oligodeoxyribonucleotide Activity," by Peter Lenert, Adam Goeken and Robert Ashman, "On the Logic of Positive Selection," by Melvin Cohn, "CTLA-4 Interacts With Stat5 and Inhibits Stat5-Mediated Transcription," by M. Srahna, L. Van Grunsven, J. Remacle and Peter Vandenberghe, and "Peritoneal Macrophages Supress T Cell Activation by Amino Acid Catabolism," by R. Matlack, K. Yeh, L. Rosini, D. Gonzalez, J. Taylor, D. Silberman, A. Pennello and James Riggs.

The intestinal immune system responds to ingested antigens in a variety of ways, ranging from tolerance to full immunity. How T cells are instructed to make these differential responses is still unclear. Dendritic cells (DCs) sample enteric antigens in the lamina propria and Peyer's patches, and transport them within the patch or to mesenteric nodes where they are presented to lymphocytes. It is probable that DCs also transmit information that influences the outcome of T cell activation, but the nature of this information and the factors in the intestine that regulate DC behavior and properties are far from clear. We have developed a model in the rat that permits analysis of DCs actually in the process of migration from the intestine to mesenteric nodes. In this paper we will review those aspects of our research that relate to antigen uptake and discuss these in the context of other experimental systems. [ABSTRACT FROM AUTHOR]

Dendritic cells capable of influencing immunity exist as functionally distinct subsets, T cell-tolerizing and T cell-immunizing subsets. The present paper reviews how these subsets of DCs develop, differentiate and function in vivo and in vitro at the cellular and molecular level. In particular, the role of DCs in the generation of regulatory T cells is highlighted. [ABSTRACT FROM AUTHOR]

Highly polymorphic age-dependent differences in progression of T and B cells have been found in various strains of inbred mice. In the immune system of C57BL/6 mice these occur first in B cells and, later in life, in T cells In this paper, we have examined the progression in the functional capacity of C57BL/6 dendritic cells (DC). Age-dependent changes were found in the syngeneic mixed leucocyte reaction, in which the stimulatory capacity of OC increased with age. This increase was independent of the age of the donor of the serum that was added lo the culture, and occurred when young donors provided the T cells. Age-dependent changes in DC properties were not detected in terms of direct plaque-forming response, response lo concanavalin A, or in the allogeneic mixed leucocyte reaction. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) have a pivotal role in instructing antigen-specific immune responses, processing and presenting antigens to CD4+ and CD8+ T cells and producing factors capable to modulate the quality of T-cell responses. In this review, we will provide an historic overview on the identification of the mechanisms controlling lymphocyte migration into the largest immune organ of the body: the gut, and we will describe how in recent years an unexpected role for DCs has emerged as the architects in programming gut-homing immune cells. Specifically, we will review how intestinal DCs utilize the dietary vitamin A metabolite retinoic acid (RA) to program gut-homing lymphocytes and how intestinal DCs acquire the unique capacity to become RA producers. [ABSTRACT FROM AUTHOR]

Background and Objective: Tolerogenic DCs (Tol-DCs), a group of cells with imDC phenotype, can stably induce T cells low-reactivity and immune tolerance. We systematically reviewed the adoptive transfusion of Tol-DCs induced by different ways to prolong cardiac allograft survival and its possible mechanism. Method: MEDLINE (1966 to March 2011), EMbase (1980 to March 2011), and ISI (inception to March 2011) were searched for identification of relevant studies. We used allogeneic heart graft survival time as endpoint outcome to analyze the effect of adoptive transfusion of Tol-DC on cardiac allograft. By integrating studies' information, we summarized the mechanisms of Tol-DC in prolonging cardiac grafts. Results: Four methods were used to induce Tol-DC in all of the 44 included studies including gene-modified, drug-intervened, cytokine-induced, and other-derived (liver-derived & spleen-derived) DCs. The results showed that all types of Tol-DC can effectively prolong graft survival, and the average extension of graft survival time for each group was as follows: 22.02 ± 21.9 days (3.2 folds to control group) in the gene modified group, 25.94 ± 16.9 days (4.3 folds) in the drug-intervened groups, 9.00 ± 8.13 days (1.9 folds) in the cytokine-induced group, and 10.69 ± 9.94 days (2.1 folds) in the other-derived group. The main mechanisms of Tol-DCs to prolong graft survival were as follows: (1) induceT-cell hyporeactivity (detected by MLR); (2) reduce the effect of cytotoxic lymphocyte (CTL); (3) promote Th2 differentiation; (4) induce Treg; (5) induce chimerism. Conclusion: For fully MHC mismatched allogeneic heart transplant recipients of inbred mouse, adoptive transfusion of Tol-DC, which can be gene-modified, drug-intervened, cytokine-induced, spleen-derived or liver-derived, can clearly prolong the survival of cardiac allograft or induce immune tolerance. Gene-modified and drug-induced Tol-DC can prolong graft survival most obviously. Having better reliability and stability than drug-induction, gene-modification is the best way to induce Tol-DCs at present. One-time intravenous infusion of 2 × 106 Tol-DC is a simple and feasible way to induce long-term graft survival. Multiple infusions will prolong it but increase the risk and cost. Adoptive transfusion of Tol-DC in conjunction with immunosuppressive agents may also prolong the graft survival time. [ABSTRACT FROM AUTHOR]

Despite novel treatment strategies, multiple myeloma (MM) remains an incurable disease with low immunogenicity and multiple immune defects. We developed an ex vivo strategy for inducing myeloma-specific cytotoxic T lymphocytes (CTLs) and demonstrate the possibility of identification and long-term in vivo monitoring of individual myeloma-specific T-cell clones using the most sensitive clonotypic assay that is able to detect low frequencies of T-cell clones (1 clonotypic cell in 106 cells). Ten patients with MM were examined for the presence of tumour-reactive T cells using dendritic cells loaded with autologous tumour cells. All patients had detectable myeloma-reactive T cells in vitro. Expanded myeloma-reactive T cells demonstrated specific cytotoxic effects against autologous tumour cells in vitro (median 39·6% at an effector:target ratio of 40:1). The clonality of myeloma-specific T cells was studied with a clonotypic assay, which demonstrated both oligoclonal and monoclonal populations of myeloma-specific T cells. CD8+ CTLs were the most immunodominant myeloma-specific T-cell clones and clinical responses were closely associated with the in vivo expansion and long-term persistence of individual CD8+ T-cell clones, usually at very low frequencies (10−3–10−6). We conclude that the clonotypic assay is the most sensitive tool for immunomonitoring of low-frequency T cells. [ABSTRACT FROM AUTHOR]

Recent intravital microscopy experiments have revealed the complex behavior of T cells within lymph nodes. Modeling T-cell responses in lymph nodes now requires integration of cell trafficking and motility with the molecular processes involved in T-cell activation. We describe an agent-based model that allows such integration, in which T cells undertake a random walk through a three-dimensional representation of the lymph node paracortex, integrating signals from dendritic cells (DCs), and proliferating in response. The model accommodates simulation of a large number of T cells packed at realistic densities, and includes dynamic cell trafficking that allows the lymph nodes to swell and shrink as the immune response progresses. The results from the model, including the kinetics of cognate T-cell proliferation and release, and the changes in their avidity profile, are similar to those observed in vivo. We therefore propose that this modeling framework is capable of successfully simulating T-cell activation while also accounting for new spatiotemporal knowledge of how T cells and DCs interact. Although some of the parameters used to drive the model are not yet experimentally validated, the model is capable of testing the effects of alternative values for any parameter on the T-cell response. We intend to refine each aspect of the model in collaboration with both theoreticians and experimentalists. [ABSTRACT FROM AUTHOR]

Antigen uptake by dendritic cells is essential for the induction of antigen-specific T-cell responses. Here, we investigate the ability of dendritic cells from different mouse strains to endocytose antigens. The uptake of different fluorescently labelled soluble antigens by bone marrow-derived dendritic cells from BALB/c, C57BL/6 and C3H/HeN mice was analysed by flow cytometry. Using transferrin as a specific marker for clathrin-mediated endocytosis, we observed no significant differences of transferrin uptake by dendritic cells from BALB/c, C57BL/6 and C3H/HeN mice. Similar results were obtained by analysing macropinocytosis with lucifer yellow. In contrast, analysing the uptake of ovalbumin, which is predominantly mediated by clathrin-mediated endocytosis via the macrophage mannose receptor, we found that dendritic cells from C3H/HeN mice take up three- to fivefold more ovalbumin than dendritic cells from BALB/c or C57BL/6 mice. Blocking the uptake of ovalbumin via the macrophage mannose receptor by using mannan led to a comparable uptake of ovalbumin by dendritic cells from all three mouse strains. Consistently, dendritic cells from C3H/HeN mice displayed significantly increased expression of the macrophage mannose receptor compared to dendritic cells from BALB/c or C57BL/6 mice. In conclusion, receptors involved in antigen uptake such as the macrophage mannose receptor may be differentially expressed and may explain variations of T-cell responses after vaccination in different individuals. [ABSTRACT FROM AUTHOR]

CD40L (CD154) expressed on activated CD4+ T cells has been shown to provide CD40+ dendritic cells (DCs), a critical signal for establishing CD8+ T-cell immunity. CD40L–CD40 interaction leads to DC maturation with IL-12 production and upregulation of various costimulatory molecules. In this study, we show that CD40 engagement provides a unique maturation signal for human monocyte-derived DCs to upregulate IL-7 production. Other inducers of DC maturation, such as TLR 4 and TLR 7/8 agonist, fail to induce IL-7 upregulation. Neutralization of IL-7 activity in human CD8+ T-cell cultures stimulated with CMV pp65-NLV peptide-pulsed mature DCs (mDCs) leads to a reduction in antigen-specific CD8+ T-cell yields suggesting a role for mDC-derived IL-7 during T-cell receptor (TCR) activation. Furthermore, IL-7 signaling requires a temporal coordination with TCR activation for maximal antigen-specific T-cell yields. These results show that CD40 signals regulate DC-derived IL-7 production that, in turn, may instruct CD8+ T cells at the time of TCR engagement for survival leading to an increased expansion of antigen-specific T cells.Immunology and Cell Biology (2009) 87, 167–177; doi:10.1038/icb.2008.80; published online 11 November 2008 [ABSTRACT FROM AUTHOR]

Dendritic cell (DC)-based immunotherapy faces new challenges because the efficacy of DC vaccines in clinical trials has been inconsistent. Strategies to improve immune responses induced by DC are currently being explored. We have recently shown the feasibility of generating fully functional DC from acute myeloid leukaemic (AML) blasts, but with varying expression levels of the important costimulatory molecule CD86. To overcome this variability, we developed a novel bispecific diabody that simultaneously and agonistically targeted CD40 on AML-DC and CD28 on naïve T cells. Beside optimization of CD28-mediated signalling, the resulting cellular cross-linking was also hypothesized to increase the strength and duration of T cell/AML-DC interactions, thus increasing T-cell responsiveness to AML antigens. The αCD40/αCD28-bispecific diabody was found to bind to its target antigens and provoked increased T-cell–DC cluster formation. The αCD40/αCD28 diabody is capable of increasing T-cell proliferation induced by AML-DC as well as the induction of DC maturation. Importantly, priming efficacy of tumour-specific cytotoxic T cells can also be improved by cross-linking AML-DC and T cells with the αCD40/αCD28 diabody. We propose that the αCD40/αCD28-bispecific diabody can serve as a potent therapeutic tool to effectively augment anti-tumour T-cell responses elicited by AML-DC. [ABSTRACT FROM AUTHOR]

Several reports have described various strategies of dendritic cell (DC) vaccination to induce specific T-cell responses in patients with acute myeloid leukaemia (AML). About 50–60% of AML cases blasts have chromosomal abnormalities, such as inv(16) or t(8,21), which could encode for leukaemia-specific antigenic peptide sequences, possibly presented in the context of self-major histocompatibility complex (MHC) molecules. As the co-culture of AML blasts with T lymphocytes seldom resulted in T-cell stimulation, we fused AML blasts with autologous DC to enhance this effect. The fusion cells expressed MHC class I and II, CD40, B7-1, B7-2, CD209 and several adhesion molecules. In a mixed lymphocyte hybrid reaction, the fusion cells induced the proliferation of autologous T cells. Moreover, in the special case of fusion cells established from AML blasts with the chromosomal abnormality inv(16), the autologous T lymphocytes could be primed to induce cytotoxicity against up to 70% autologous AML blasts in a effector:target ratio of 20:1. Blocking assays demonstrated that the lysis was chiefly mediated by CD8+, CCR7− T lymphocytes, which could be further expanded in the form of effector memory CD8+ T cells by repeated co-cultures with the autologous fusion cells. [ABSTRACT FROM AUTHOR]

Recently, we have described a soluble survival signal for activated lymphocytes from CD14+ cells. As a result of the importance of T lymphocytes in the pathogenesis of rheumatoid arthritis (RA), we speculate a possible role for CD14+ cells in supporting the outgrowth of autoreactive lymphocytes in RA. To address this issue further, supernatants from activated CD14+ cells (CD14 cocktails) in both normal controls and RA patients were collected. The relative strength of the CD14 cocktails from normal controls and RA patients was compared. The data showed that depletion of CD14+ calls resulted in a much higher increase of activation-induced cell death (AICD) and a decrease of lymphocyte proliferation in the peripheral blood mononuclear cells of RA patients compared to normal controls. Interestingly, CD14 cocktails from RA patients provide much stronger protection against AICD compared to those from normal controls. The observed soluble survival signal from CD14+ cells is a general phenomenon because CD14 cocktails prevent both phytohaemagglutinin A-p- and anti-CD3-induced AICD. Furthermore, supernatants collected from human dendritic cell cultures also prevent activated lymphocytes from undergoing AICD. The data implicate an important role of the CD14+ cell and its secreted form of survival signal in the pathogenesis of RA. [ABSTRACT FROM AUTHOR]

Twenty-five years ago, when I delivered the inaugural lecture of the Scandinavian Society for Immunology, my mind was filled with germinal centres because of the extraordinary antigen-capturing mechanism there, which depended on follicular dendritic cells trapping the antigen and holding it in an extracellular location for long periods of time, following which the germinal centre reaction developed around the antigen depot. It was apparent that germinal centres had much to do with immunological memory, but few functional details of their role were known. In the intervening period, a great deal of knowledge has accumulated about germinal centres, which have become known as the sites of extensive B cell proliferation, immunoglobulin variable region gene hypermutation, and selection of better antigen-binding variants leading to affinity maturation in the antibody response. Our laboratory's interest was reawakened when we came to examine the hypothesis that B lymphocytes destined to develop into memory B cells might pass through a 'second window' of tolerance susceptibility if they encountered antigen in the absence of T-cell help. We have constructed a model of tolerance dependent on the injection of soluble deaggregated antigen before or even up to 6 days after T cell-dependent challenge immunization. The model was intended to mimic what might happen if a B cell, developing correctly in a germinal centre, fortuitously mutates to acquire cross-reactivity to a soluble self antigen. We have shown that the surrogate self-antigen can profoundly impair the germinal centre process and virtually stop the emergence of high affinity memory B cells. We show further that this effect is mediated through both B and T cells. Nevertheless, the formation of germinal centres as such is not stopped but rather the processes inside germinal centres are substantially modified. The end result is a gross deficit in high affinity anti-NP memory B cells and a moderate reduction in lower affinity B cells. Further work is in progress to analyse the VH gene mutations in tolerant animals, and to examine the hypothesis that antigen can cause apoptotic cell death in higher affinity germinal centre B cells. [ABSTRACT FROM AUTHOR]

We describe the effects of treatment with topical steroids or dithranol on T and dendritic cells in the skin of patients with chronic plaque psoriasis. Resolution of lesions by both types of topical treatments was accompanied by a marked decrease in epidermal T cells. In steroid treated lesions there was also a reduction in DR+ dendritic cells to normal numbers during treatment and the rate of disappearance of both cell types correlated with the rate of resolution. However, a significant reduction of dendritic cells was not usually observed until after the T ceils had almost disappeared from the epidermis and substantial healing of lesions had taken place. Dendritic cells in steroid-treated uninvolved skin had decreased to a lower level than in normal skin. In contrast, dithranol did not affect dendritic cell, either in lesional or in unaffected psoriatic epidermis. The decrease in dermal T cells observed with both treatments was more marked in steroid-treated lesions and correlated with resolution. However, blood T cells were unaffected by both treatments. The findings provide further support for the role of T cells in the pathogenesis of psoriasis. [ABSTRACT FROM AUTHOR]

Accessory cell (A cell) functions of splenic dendritic cells (DC) and peritoneal macrophages (Mφ) were investigated in the Con A-stimulated proliferative response of thymic T cells. DC were more efficient as A cells than Mφ in respect of their necessary cell numbers, Con A dose and culture period required for optimal response. Con A-pulsed T cells proliferated with the aid of lymphocyte activating factor(s) (LAF) derived from Mφ, even in the apparent absence of A cells. Con A-pulsed Mφ were superior to unpulsed Mφ in the secretion of LAF to induce a high response of Con A-pulsed T cells. A cell activity of Mφ in different preparations appeared to parallel the ability to secrete LAF, and was totally abolished by fixation of Mφ with paraformaldehyde. The fixation of DC, however, resulted in only a partial reduction of the A cell activity. These results argue that both DC and Mφ can serve as A cells in the T-cell response to Con A, but that the mechanism to manifest A cell activity is somewhat different between DC and Mφ. [ABSTRACT FROM AUTHOR]