Patient perception of the benefit of a BRAF inhibitor in metastatic melanoma: quality-of-life analyses of the BREAK-3 study comparing dabrafenib with dacarbazine.

BACKGROUND: In a randomized phase III study (BREAK-3), dabrafenib showed prolonged progression-free survival (PFS) (median 5.1 versus 2.7 months; hazard ratio = 0.30; 95% confidence interval 0.18-0.53; P < 0.0001) compared with dacarbazine (DTIC) in patients with BRAF V600E metastatic melanoma. Assessing how these results are transformed into a real health benefit for patients is crucial. METHODS: The EORTC QLQ-C30 questionnaire assessed quality of life (QoL) at baseline and follow-up visits. RESULTS: For DTIC, all functional dimensions except role dimension worsened from baseline at follow-up. For dabrafenib, all functionality dimensions remained stable relative to baseline or improved at week 6; mean change in seven symptom dimensions improved from baseline, with appetite loss, insomnia, nausea and vomiting, and pain showing the greatest improvement. In the DTIC arm, symptom dimensions were unchanged or worsened from baseline for all symptoms except pain (week 6), with the greatest exacerbations observed for fatigue and nausea and vomiting. Mixed-model-repeated measures analyses showed significant (P < 0.05) and/or clinically meaningful improvements from baseline in favor of dabrafenib for emotional and social functioning, nausea and vomiting, appetite loss, diarrhea, fatigue, dyspnea, and insomnia at weeks 6 and/or 12. After crossing over to dabrafenib upon progression (n = 35), improvements in all QoL dimensions were evident after receiving dabrafenib for 6 (n = 31) to 12 (n = 25) weeks. CONCLUSIONS: This first reported QoL analysis for a BRAF inhibitor in metastatic melanoma demonstrates that the high tumor response rates and PFS superiority of dabrafenib over DTIC is not only a theoretical advantage, but also transforms in a rapid functional and symptomatic benefit for the patient. ClinicalTrials.gov Identifier: NCT01227889.

Tumor necrosis factor alpha maintains the viability of murine epidermal Langerhans cells in culture, but in contrast to granulocyte/macrophage colony-stimulating factor, without inducing their functional maturation.

Freshly isolated murine epidermal Langerhans cells (LC) are weak stimulators of resting T cells but increase their stimulatory capacity 10-30-fold upon 2-3 d of culture together with other epidermal cells. This maturation of LC is mediated by two keratinocyte products. Granulocyte/macrophage colony-stimulating factor (GM-CSF) maintains viability and increases function. IL-1 alone does not keep LC alive, but when combined with GM-CSF further enhances their stimulatory activity. We have now searched for a cytokine that would keep LC in a viable, but functionally immature state. When LC (enriched to greater than 75%) were cultured in the presence of GM-CSF (2 ng/ml) or murine (TNF-alpha) (plateau effect at 62 U/ml), the recovery of viable LC after 72 h was identical. The LC cultured in murine TNF-alpha, however, were 10-30 times less active in stimulating resting T cells. A series of experiments demonstrated that this phenomenon was not due to the induction of insufficient amounts of GM-CSF, the induction of a suppressor factor, or a toxic effect of TNF-alpha. Interestingly, the observed TNF-alpha activity exhibited a species preference, as human TNF-alpha was not active at comparable doses. We have observed an unexpected effect of TNF-alpha on LC in vitro. Though we found that freshly prepared epidermal cells express TNF-alpha mRNA, further studies are needed to establish whether TNF-alpha plays a role in vivo by keeping resident LC in a viable, but functionally immature state.

Cytokine gene expression in murine epidermal cell suspensions: interleukin 1 beta and macrophage inflammatory protein 1 alpha are selectively expressed in Langerhans cells but are differentially regulated in culture.

Epidermal Langerhans cells (LC) are considered direct yet immature precursors of dendritic cells (DC) in the draining lymph nodes. Although the development of LC into potent immunostimulatory DC occurs in vitro and has been studied in detail, little is known about their profile of cytokine gene expression. By using reverse transcriptase polymerase chain reaction analysis to screen 16 cytokines followed by Northern blotting for selected analysis, we determined the cytokine gene expression profile of murine LC at different time points in culture when T cell stimulatory activity is increasing profoundly. LC regularly expressed macrophage inflammatory proteins, MIP-1 alpha and MIP-2, and interleukin 1 beta (IL-1 beta). Both MIPs were downregulated upon culture and maturation into DC, whereas IL-1 beta was strongly upregulated in culture. MIP-1 alpha and IL-1 beta mRNA were found only in LC, but not in other epidermal cells. Apart from trace amounts of IL-6 in cultured LC, several macrophage and T cell products were not detected. The cytokine expression profile of LC thus appears distinct from typical macrophages. The exact role of the cytokine genes we found transcribed in LC remains to be determined.

Disappearance of certain acidic organelles (endosomes and Langerhans cell granules) accompanies loss of antigen processing capacity upon culture of epidermal Langerhans cells.

Freshly isolated epidermal Langerhans cells (LC) can actively process native protein antigens, but are weak in sensitizing helper T cells. During culture, when LC mature into potent immunostimulatory dendritic cells, T cell sensitizing capacity develops but antigen processing capacity is downregulated. Processing of exogenous antigens for class II-restricted antigen presentation involves acidic organelles. We used the DAMP-technique to monitor acidic organelles at the ultrastructural level in fresh, as well as cultured, mouse and human LC. We observed that the loss of antigen processing capacity with culture of LC was reflected by the disappearance of certain acidic organelles, namely endosomes (particularly early ones), and the hitherto enigmatic LC granules ("Birbeck Granules"). Our findings support the notion that endosomes are critical for antigen processing and suggest that LC granules might be involved as well.

Understanding the dendritic cell lineage through a study of cytokine receptors.

Dendritic cells form a system of antigen presenting cells that are specialized to stimulate T lymphocytes, including quiescent T cells. The lineage of dendritic cells is not fully characterized, although prior studies have shown that growth and differentiation are controlled by cytokines, particularly granulocyte/macrophage colony-stimulating factor (GM-CSF). To further elucidate the nature and control of the dendritic cell lineage, we have studied the expression of specific cytokine receptors. Sufficient numbers of dendritic cells were purified from spleen and skin to do quantitative binding studies with radiolabeled M-CSF, GM-CSF, and interleukin 1 (IL-1). To verify the nonlymphoid nature of dendritic cells, we made an initial search for rearrangements in T cell receptor and immunoglobulin genes and none were found. M-CSF binding sites, a property of mononuclear phagocytes, also were absent. In contrast, GM-CSF receptors were abundant on mature dendritic cells, with approximately 3,000 binding sites/cell with a single Kd of 500-1,000 pM. Substantial numbers of high affinity (< 100 pM) IL-1 binding sites were identified as well; cultured epidermal dendritic cells (i.e., epidermal Langerhans cells) had 500/cell and spleen dendritic cells approximately 70/cell. Cross-linking approaches showed the 80-kD species that is expected of high-affinity type 1 IL-1 receptor. Anti-type 1 IL-1 receptor (R) mAbs also visualized these receptors by flow cytometry on freshly isolated epidermal dendritic cells. These results provide new evidence that dendritic cells represent a differentiation pathway distinct from lymphocytes and monocytes. Together with recent findings on the effects of IL-1 and GM-CSF on epidermal dendritic cells in situ (see Results and Discussion), the data lead to a proposal whereby IL-1 signals IL-1R to upregulate GM-CSF receptors and thereby, the observed responsiveness of dendritic cells to GM-CSF for growth, viability, and function.

High level IL-12 production by murine dendritic cells: upregulation via MHC class II and CD40 molecules and downregulation by IL-4 and IL-10.

We have shown previously that dendritic cells (DC) produce IL-12 upon interaction with CD4+ T cells. Here we ask how this IL-12 production is induced and regulated. Quantitative PCR and in situ hybridization for IL-12 p40 and an ELISA specific for the p70 heterodimer were used to determine IL-12 production. We demonstrate that ligation of either CD40 or MHC class II molecules independently trigger IL-12 production in DC, and that IL-12 production is downregulated by IL-4 and IL-10. The levels of bioactive IL-12 that can be released by triggering with an anti-CD40 mAb or with a T cell hybridoma are high (range 260-4700 pg/ml from 1 X 10(6) DC in 72 h). The CD40-mediated pathway indicates that IL-12 production is induced in DC upon interaction with activated, CD40 ligand-expressing helper T cells, even in the absence of cognate antigen recognition. Side-by-side comparison of IL-12 production, and blocking experiments employing an anti-CD40 ligand mAb, suggest that the CD40-mediated pathway is quantitatively more significant than induction via the MHC class II molecule. The importance of the CD40/CD40 ligand interaction for IL-12 induction in DC likely contributes to the recent finding that mice lacking the CD40 ligand are impaired in mounting Th1 type cell-mediated immune responses.

Proliferating dendritic cell progenitors in human blood.

CD34+ cells in human cord blood and marrow are known to give rise to dendritic cells (DC), as well as to other myeloid lineages. CD34+ cells are rare in adult blood, however, making it difficult to use CD34+ cells to ascertain if DC progenitors are present in the circulation and if blood can be a starting point to obtain large numbers of these immunostimulatory antigen-presenting cells for clinical studies. A systematic search for DC progenitors was therefore carried out in several contexts. In each case, we looked initially for the distinctive proliferating aggregates that were described previously in mice. In cord blood, it was only necessary to deplete erythroid progenitors, and add granulocyte/macrophage colony-stimulating factor (GM-CSF) together with tumor necrosis factor (TNF), to observe many aggregates and the production of typical DC progeny. In adult blood from patients receiving CSFs after chemotherapy for malignancy, GM-CSF and TNF likewise generated characteristic DCs from HLA-DR negative precursors. However, in adult blood from healthy donors, the above approaches only generated small DC aggregates which then seemed to become monocytes. When interleukin 4 was used to suppress monocyte development (Jansen, J. H., G.-J. H. M. Wientjens, W. E. Fibbe, R. Willemze, and H. C. Kluin-Nelemans. 1989. J. Exp. Med. 170:577.), the addition of GM-CSF led to the formation of large proliferating DC aggregates and within 5-7 d, many nonproliferating progeny, about 3-8 million cells per 40 ml of blood. The progeny had a characteristic morphology and surface composition (e.g., abundant HLA-DR and accessory molecules for cell-mediated immunity) and were potent stimulators of quiescent T cells. Therefore, large numbers of DCs can be mobilized by specific cytokines from progenitors in the blood stream. These relatively large numbers of DC progeny should facilitate future studies of their Fc epsilon RI and CD4 receptors, and their use in stimulating T cell-mediated resistance to viruses and tumors.

Vaccination with mage-3A1 peptide-pulsed mature, monocyte-derived dendritic cells expands specific cytotoxic T cells and induces regression of some metastases in advanced stage IV melanoma.

Dendritic cells (DCs) are considered to be promising adjuvants for inducing immunity to cancer. We used mature, monocyte-derived DCs to elicit resistance to malignant melanoma. The DCs were pulsed with Mage-3A1 tumor peptide and a recall antigen, tetanus toxoid or tuberculin. 11 far advanced stage IV melanoma patients, who were progressive despite standard chemotherapy, received five DC vaccinations at 14-d intervals. The first three vaccinations were administered into the skin, 3 x 10(6) DCs each subcutaneously and intradermally, followed by two intravenous injections of 6 x 10(6) and 12 x 10(6) DCs, respectively. Only minor (less than or equal to grade II) side effects were observed. Immunity to the recall antigen was boosted. Significant expansions of Mage-3A1-specific CD8(+) cytotoxic T lymphocyte (CTL) precursors were induced in 8/11 patients. Curiously, these immune responses often declined after the intravenous vaccinations. Regressions of individual metastases (skin, lymph node, lung, and liver) were evident in 6/11 patients. Resolution of skin metastases in two of the patients was accompanied by erythema and CD8(+) T cell infiltration, whereas nonregressing lesions lacked CD8(+) T cells as well as Mage-3 mRNA expression. This study proves the principle that DC "vaccines" can frequently expand tumor-specific CTLs and elicit regressions even in advanced cancer and, in addition, provides evidence for an active CD8(+) CTL-tumor cell interaction in situ as well as escape by lack of tumor antigen expression.

Transfer of mRNA encoding recombinant immunoreceptors reprograms CD4+ and CD8+ T cells for use in the adoptive immunotherapy of cancer.

Human T lymphocytes can be redirected with a new defined specificity by expression of a chimeric T-cell receptor (immunoreceptor) for the use in adoptive immunotherapy of cancer. Whereas standard procedures use retroviral gene transduction to constitutively express immunoreceptors in T cells, we here explored for the first time mRNA electroporation to achieve transient immunoreceptor expression, and thereby minimizing the risk of persistence of potential autoaggression. CD4(+) and CD8(+) T cells were efficiently transfected with immunoreceptors specific for ErbB2 and CEA. The immunoreceptor expression was transient with half-maximal expression at day 2 and no detectable immunoreceptor expression at day 9 after electroporation. Immunoreceptor-transfected T cells were specifically activated upon coincubation with ErbB2(+) and CEA(+) tumor cells, respectively, resulting in secretion of interferon-gamma (IFNgamma), interleukin-2 (IL-2), and tumor necrosis factor-alpha (TNFalpha). Furthermore, immunoreceptor-transfected CD8(+) T cells specifically lysed ErbB2(+) and CEA(+) tumor cells, respectively. The RNA-transfected T cells retained their cytotoxic function after 2 days of activation and exhibited cytolytic activities like retrovirally transduced T cells. RNA electroporation of T cells thereby provides a versatile tool for transient immunoreceptor expression, which may be of advantage in avoiding the persistence of unintended autoaggression.

[Malignant melanoma of the lacrimal sac]. / Malignes Melanom des Tränensacks.

A 68-year-old woman presented with a 10-month history of right-sided epiphora, bloody tears, and medial canthal mass. Computed tomography revealed a soft tissue mass of the right lacrimal sac with widening of the bony nasolacrimal canal. External dacryocystorhinostomy with incisional biopsy confirmed the diagnosis of malignant melanoma. After staging, further therapy included orbital exenteration, lateral rhinotomy with en bloc resection of the lacrimal drainage apparatus, and adjuvant radioimmunotherapy. One year after surgery, no evidence of local recurrence or metastatic disease could be detected.

Differential susceptibility to CD95 (Apo-1/Fas) and MHC class II-induced apoptosis during murine dendritic cell development.

Disappearance of antigen presenting cells (APC) from the lymph node occurs following antigen specific interactions with T cells. We have investigated the regulation of CD95 (Apo-1/Fas) induced apoptosis during murine dendritic cell (DC) development. Consistent with the moderate levels of CD95 surface expression and low, or absent, MHC class II expression, immature DC in bone marrow cultures were highly sensitive to CD95 induced apoptosis, but insensitive to class II mediated apoptosis. In contrast, mature splenic, epidermal and bone marrow derived DC were fully resistant to CD95 induced cell death, but sensitive to class II induced apoptosis. Although caspase 3 and 8 activation was detected in immature DC undergoing CD95L-induced apoptosis, the pan-caspase inhibitor zVAD-fmk did not inhibit the early events of CD95-induced mitochondrial depolarisation or phosphatidyl serine exposure and only partially inhibited the killing of immature DC. In contrast, zVAD-fmk was completely effective in preventing CD95L mediated death of murine thymocytes. Collectively, these data do not support a major role of CD95: CD95L ligation in apoptosis of mature DC, but rather emphasise the existence of distinct pathways for the elimination of DC at different stages of maturation.

Migration of dendritic cells within 3-D collagen lattices is dependent on tissue origin, state of maturation, and matrix structure and is maintained by proinflammatory cytokines.

The function of dendritic cells (DC) depends on active migration through three-dimensional (3-D) extracellular matrices. We have analyzed the migration of murine DC from different tissue origins within 3-D collagen lattices through the use of time-lapse videomicroscopy and single-cell tracking. Directly after incorporation, 50-90% of DC from the spleen (spDC) and Langerhans cells freshly isolated from the epidermis (fLC) displayed active motility in these matrices. Whereas mature spDC showed multilateral pseudopod dynamics as well as fast and heterogeneous migration, immature fLC displayed a spherical shape with faint membrane processes and very homogenous, slow migration characteristics. In the absence of external stimuli, migration of both, spDC and fLC, vanished after >36 h due to cell death. Maintaining fLC viability by external granulocyte-macrophage colony-stimulating factor or tumor necrosis factor alpha prolonged migration up to 5 days. During this period fLC transformed into mature cells with large dendrites, thereby developing a heterogeneous migration pattern more similar to spDC. In randomly polymerized collagen matrices cell paths were without preferential orientation. In contrast, in artificially aligned lattices directional paths in accordance with the forced fiber orientation were observed. Thus, migration is an inherent property of DC, largely influenced by tissue origin, degree of maturity, and the 3-D structure of the environment.

Immunotherapy of metastatic malignant melanoma by a vaccine consisting of autologous interleukin 2-transfected cancer cells: outcome of a phase I study.

We performed a phase I trial to evaluate the safety and tolerability of repeated skin injections of IL-2-transfected autologous melanoma cells into patients with advanced disease. Cell suspensions, propagated from excised metastases, were IL-2 gene transfected by adenovirus-enhanced transferrinfection and X-irradiated prior to injection. Vaccine production was successful in 54% of the patients. Fifteen patients (37%) received two to eight skin vaccinations of either 3 x 10(6) (intradermal) or 1 x 10(7) (half intradermal, half subcutaneous) transfected melanoma cells per vaccination (secreting 140-17,060 biological response modifier program units of IL-2/10(6) cells/24 hr). Analyses of safety and efficacy were carried out in 15 and 14 patients, respectively. Overall, the vaccine was well tolerated. All patients displayed modest local reactions (erythema, induration, and pruritus) and some experienced flu-like symptoms. Apart from newly appearing (4 of 14) and increasing (5 of 14) anti-adenovirus and newly detectable anti-nuclear antibody titers (1 of 15), recipients developed de novo or exhibited increased melanoma cell-specific delayed-type hypersensitivity (DTH) reactions (8 of 15) and vitiligo (3 of 15) and showed signs of tumor regression (3 of 15). This supports the idea of a vaccine-induced or -amplified anti-cancer immune response. None of the patients exhibited complete or partial regressions, but five of them experienced periods of disease stabilization. Three of these individuals received more than the four planned vaccinations and their mean survival time was 15.7 +/- 3.5 months as compared to 7.8 +/- 4.6 months for the entire patient cohort. These data indicate that IL-2-producing, autologous cancer cells can be safely administered to stage IV melanoma patients and could conceivably be of benefit to patients with less advanced disease.

Effective enrichment of murine epidermal Langerhans cells by a modified(mismatched) panning technique.

A method for the enrichment of murine epidermal Langerhans cells (LC) is described in detail. It is based on positive selection of LC from pre-enriched fresh or cultured epidermal cell suspensions derived from ear skin by a modified panning technique. The method uses the interspecies cross-reactivities of anti-immunoglobulin antibodies: when LC in an epidermal cell suspension are labeled with mouse anti-major histocompatibility complex (MHC) class II antibodies they bind to petri dishes coated with anti-rat immunoglobulin antibodies. We therefore call this method "mismatched panning." After rinsing off non-adherent cells, the adherent LC can easily be dislodged by adding excess amounts of rat immunoglobulins, which effectively compete with the LC-bound mouse anti-MHC class II antibodies for binding to the petri dish. Using this modified panning technique, both fresh and cultured LC could be enriched up to more than 90% purity. From one ear, 2.0-3.0 x 10(4) fresh LC and 3.0-4.5 x 10(4) cultured LC could be obtained. Of all LC present in a primary, unenriched epidermal cell suspension, 40-60% were recovered when panned immediately after isolation of the epidermal cells and 50-75% when panned after 3 d of epidermal cell culture. Viability of panned LC was consistently more than 90%. Antigen presenting and T-cell-stimulating capacity of LC and responses to the cytokines granulocyte/macrophage colony-stimulating factor and tumor necrosis factor-alpha were not impaired by this panning procedure. The major advantage of this method compared to pre-existing panning techniques is the ease with which adherent LC can be dislodged from the panning dishes. Because the elution procedure is very gentle, virtually all panned LC are viable. As a consequence, good yields of highly enriched LC can be obtained in a reasonable time.

Predominant expression of Fas (CD95) ligand in metastatic melanoma revealed by longitudinal analysis.

The expression of Fas ligand has recently been proposed as a novel tumor escape mechanism for melanoma. To establish the characteristics of Fas ligand expression during the course of melanoma progression we performed a longitudinal study analyzing primary tumors as well as subsequently evolving metastases. In primary melanoma Fas ligand was expressed in two of 20 lesions; this expression was weak and restricted to few parts of the tumors. The Fas ligand positive primary melanomas were rather thick, i.e., 8.5 and 3.8 mm, versus a median of 2.4 mm of the remaining tumors. In contrast, for metastatic melanoma Fas ligand expression was present in six of 11 cases investigated. The metastases of primary tumors displaying Fas ligand maintained its expression. As Fas ligand positive melanoma cells are capable of inducing apoptosis in susceptible cells, e.g., Fas positive tumor infiltrating lymphocytes, we tested for the presence of apoptotic cells in situ by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. This analysis revealed that apoptotic cells were present within the Fas ligand positive tumors. The number of apoptotic cells, however, never exceeded 5% of the total cells. Thus, Fas ligand mediated apoptosis does not seem to be a major immune escape mechanism for melanoma but its expression correlates with the stage of melanoma.

Generation of mature dendritic cells from human blood. An improved method with special regard to clinical applicability.

Two methods to generate human dendritic cells from hematopoietic precursor cells in peripheral blood have recently been published. One approach utilizes the rare CD34+ precursors and GM-CSF plus TNF-alpha. The other method makes use of the more abundant CD34- precursor population and GM-CSF plus IL-4. Here we report a method that is based on the latter approach. However, the GM-CSF and IL-4 treated cells are not stable mature dendritic cells, e.g., the characteristic morphology and nonadherence of dendritic cells is lost if the cytokines are removed. We describe the need for a monocyte-conditioned medium to generate fully mature and stable dendritic cells. This is achieved by adding a 3 day 'maturation culture' to the initial 6-7 day culture in the presence of GM-CSF and IL-4. Macrophage-conditioned medium contains the critical maturation factors. Mature dendritic cells are defined by their pronounced display of motile cytoplasmic processes ('veils'), their high capacity to induce proliferative responses in resting T cells, particularly in naive umbilical cord T cells, their down-regulated antigen processing ability, and their characteristic phenotype: expression of CD83, high levels of MHC molecules and CD86, lack of CD115 and perinuclear dot-like CD68 staining. These features are stable for at least 3 days upon withdrawal of cytokines and conditioned media. IL-4 can be replaced by IL-13. When CD34+ progenitors are depleted from blood, there is only a minor reduction in the yield of dendritic cells by this method. We have adapted the method to consider several variables that are pertinent to clinical use, including a change from fetal calf serum to human plasma and to media approved for clinical use like X-VIVO or AIM-V. 1% plasma and RPMI 1640 are currently optimal. Additional reagents used for cell culture (Ig. cytokines) and cell separation (immunomagnetic beads) are approved for or already used in clinical applications. For 40 ml blood, the yield is 0.8-3.3 x 10(6) mature dendritic cells as defined by the expression of the new dendritic cell-restricted marker CD83. CD83+ cells constitute between 30 and 80% of all cells recovered at the end of the culture period. Yields can be enhanced up to six-fold if the blood donors are pretreated with G-CSF. Stable, mature dendritic cells generated by this method should be a powerful tool for active immunotherapy.

Generation of large numbers of fully mature and stable dendritic cells from leukapheresis products for clinical application.

Dendritic Cell (DC)-based vaccination approaches in man require a reproducible DC generation method that can be performed in conformity with GMP (Good Manufacturing Practice) guidelines and that circumvents the need for multiple blood drawings to generate DC. To this end we modified our previously described method to generate mature DC from CD14 + monocytes by a two step method (priming in GM-SF + IL-4 followed by maturation in monocyte conditioned medium) for use with leukapheresis products as a starting population. Several adaptations were necessary. We established, for example, a modified adherence step to reliably enrich CD14 + DC precursors from apheresis mononuclear cells. The addition of GM-CSF + IL-4 at the onset of culture proved disadvantageous and was, therefore, delayed for 24 h. DC development from apheresis cells occurred faster than from fresh blood or buffy coat, and was complete after 7 days. Monocyte conditioned medium when added on day 6 resulted in fully mature and stable DC (veiled, highly migratory and T cell sensitizing cells with a characteristic phenotype such as 85% CD83 + , p55/fascin + , CD115/M-CSF-R - , CD86 + ) already after 24 h. The mature DC progeny were shown to remain stable and viable if cultured for another 1-2 days in the absence of cytokines, and to be resistant to inhibitory effects of IL-10. Freezing conditions were established to generate DC from frozen aliquots of PBMC or to freeze mature DC themselves for later use. The approach yields large numbers of standardized DC (5-10 x 10(8) mature CD83 + DC/leukapheresis) that are suitable for performing sound DC-based vaccination trials that can be compared with each other.

Functions of myeloid and lymphoid dendritic cells.

The bone marrow derived dendritic cell (DC) is an essential antigen presenting cell (APC) for the initiation of primary, T cell based immune responses. DC are a heterogenous haematopoietic lineage, in that many subsets from different tissues show different surface phenotypes, but the ability to stimulate antigen specific naïve T cell proliferation appears to be shared between these DC subsets. It has been suggested that the so called myeloid and lymphoid-derived subsets of DC perform distinct stimulatory or tolerogenic functions. However, recent data has blurred this apparent distinction of DC subset function and shown that both subsets are at least capable of stimulatory and possibly even tolerogenic functions. Thus, the immunoregulatory potential of DC may depend less on ontology than on recent activatory or downregulatory stimuli.

Dendritic cell production of cytokines and responses to cytokines.

Dendritic cells (DC) are a family of bone marrow-derived MHC class II expressing cells which occur in small numbers in most lymphoid and nonlymphoid tissues. They represent a distinct lineage of leukocytes which can be found in two distinct maturational stages: immature dendritic cells are exemplified by the Langerhans cells in the epidermis, and are considered to be precursors to the mature dendritic cells in the lymphoid organs. These maturational stages can be distinguished by phenotypic and functional characteristics. Immature dendritic cells are weak stimulators of resting T lymphocytes but are excellent in processing soluble protein antigens for presentation to T cell clones. Mature dendritic cells show exactly reciprocal features. In this review the relatively few available data on cytokine production by DC and responses of DC to cytokines are collected. Our goal is to consider the role of cytokines in DC function including the transition from immature to mature stages.