Multidimensional flow-cytometric analysis of dendritic cells in peripheral blood of normal donors and cancer patients

Versatile exclusion-based sample preparation platform for integrated rare cell isolation and analyte extraction

Rare cell populations provide a patient-centric tool to monitor disease treatment, response, and resistance. However, understanding rare cells is a complex problem, which requires cell isolation/purification and downstream molecular interrogation - processes challenged by non-target populations, which vary patient-to-patient and change with disease. As such, cell isolation platforms must be amenable to a range of sample types while maintaining high efficiency and purity. The multiplexed technology for automated extraction (mTAE) is a versatile magnetic bead-based isolation platform that facilitates positive, negative, and combinatorial selection with integrated protein staining and nucleic acid isolation. mTAE is validated by isolating circulating tumor cells (CTCs) - a model rare cell population - from breast and prostate cancer patient samples. Negative selection yielded high efficiency capture of CTCs while positive selection yielded higher purity with an average of only 95 contaminant cells captured per milliliter of processed whole blood. With combinatorial selection, an overall increase in capture efficiency was observed, highlighting the potential significance of integrating multiple capture approaches on a single platform. Following capture (and staining), on platform nucleic acid extraction enabled the detection of androgen receptor-related transcripts from CTCs isolated from prostate cancer patients. The flexibility (e.g. negative, positive, combinatorial selection) and capabilities (e.g. isolation, protein staining, and nucleic acid extraction) of mTAE enable users to freely interrogate specific cell populations, a capability required to understand the potential of emerging rare cell populations and readily adapt to the heterogeneity presented across clinical samples.

Changes in Circulating Dendritic Cells and IL-12 in Relation to the Angiogenic Factor VEGF during IL-2 Immunotherapy of Metastatic Renal Cell Cancer

Angiogenesis and immunosuppression are the main biological mechanisms responsible for cancer progression. Moreover, recent observations suggesting a negative influence of angiogenesis on anticancer immunity have shown that some angiogenic factors, such as VEGF, may induce immunosuppression. In addition, the evidence of abnormally high blood levels of VEGF has been proven to be associated with resistance to IL-2 immunotherapy. The present study was performed to establish a possible relation ship between the efficacy of IL-2 cancer immunotherapy and changes in circulating levels of VEGF, IL-12, mature and immature dendritic cells (DC). The study included 25 metastatic renal cell cancer patients who underwent subcutaneus low-dose IL-2 immunotherapy (6 MIU/day for 6 days/week for 4 weeks). Immature and mature DCs were identified as CD123+ and CD11c+ cells, respectively. The clinical response consisted of partial response (PR) in five, stable disease (SD) in 11 and progressive disease (PD) in the remaining nine patients. The mean IL-12 levels observed during IL-2 immunotherapy were significantly higher in patients with PR or SD than in those with PD, whereas the mean VEGF concentrations were significantly higher in patients who had PD than in those with PR or SD. Finally, a significant increase in the mean number of circulating mature DCs occurred only in patients with PR or SD, whereas no significant change was seen in patients with PD. By contrast, no significant change was observed in the mean number of immature DCs. This study shows that the efficacy of IL-2 immunotherapy is associated with a significant increase in circulating mature DCs and IL-12, without any concomitant increase in VEGF concentrations. Further studies will be required to better define the relationship between activation of anticancer immunity and control of angiogenesis-related mechanisms.

Circulating Immature and Mature Dendritic Cells in Relation to Lymphocyte Subsets in Patients with Gastrointestinal Tract Cancer

Cancer-related deficiency in circulating dendritic cells (DC), whose important anticancer role is well established, has been proven to be associated with lymphocytopenia. This study was performed to evaluate which lymphocyte subset is most markedly related to the failure of the DC system. The study included 30 patients with gastrointestinal tract cancer, 10 of whom had distant organ metastases. Immature and mature DCs were measured by FACS and monoclonal antibodies against CD123 and CD11c antigens, respectively. Low levels of immature and mature DCs were observed in 63% and 43% of patients, respectively. Patients with low levels of circulating mature DCs had significantly lower values of T lymphocytes, T helper lymphocytes and NK cells than those with normal mature DC levels. In contrast, no significant difference was seen between patients with normal or abnormally low values of immature DCs. Conversely, patients with a decreased number of T lymphocytes, T helper lymphocytes and NK cells showed significantly lower values of circulating mature DCs than those with lymphocyte subsets within the normal range, whereas no difference was seen in immature DC amounts. This study suggests that only mature DC deficiency may be associated with important lymphocyte subset alterations in cancer patients, whereas deficiency in immature DCs does not seem to be related to other immune cell disorders.

B cell-specific protein FCRLA is expressed by plasmacytoid dendritic cells in humans

BACKGROUND

Fc receptor-like A (FCRLA) is a unique member of a family of Fc receptor like-molecules that lacks a transmembrane region and is an ER-resident protein. In mice and humans, FCRLA has been known as a B cell specific protein. We report here that, in humans, FCRLA is also expressed in a subpopulation of plasmacytoid dendritic cells (pDCs).

METHODS

Human peripheral blood mononuclear cells (PBMC), splenocytes, and tonsillar cells were stained for lineage markers followed by fixation/saponin permeabilization and intracellular staining for FCRLA, and then analyzed by flow cytometry with CD123 and CD303 used as pDC markers.

RESULTS

We conducted an extensive flow cytometric analysis of a rare population of CD19-FCRLA+ cells found for the first time in human lymphoid tissues that we assigned to pDCs as they were lin-/CD123+/CD303+. FCRLA expression in human pDCs was further confirmed by the RT-PCR analysis of cDNA of pDCs isolated from the peripheral blood of a healthy donor. FCRLA-positive pDCs expressed a lower level of HLA-DR than their FCRLA-negative counterparts.

CONCLUSIONS

FCRLA has long been viewed as a B cell specific protein, and this is the first time its expression has also been shown in human pDCs. © 2017 International Clinical Cytometry Society.

Recovery of Lymphocyte and Dendritic Cell Subsets Following Reduced Intensity Allogeneic Bone Marrow Transplantation

Approaches using reduced conditioning regimens have been developed to obtain minimal procedure-related toxicity. Such novel therapeutic options are being explored with good preliminary results concerning feasibility and engraftment. However, many aspects remain under-evaluated and few data are available about immune and dendritic cell (DC) reconstitution after these highly immunosuppressive regimens. We present here our data in 20 patients receiving allogeneic bone marrow transplantation (allo-BMT) using a reduced preparative regimen. We evaluated in the first 3 months following allo-BMT, several immunological parameters including DC subsets, and compared these to historical results obtained in a group of myeloablative allo-BMT patients. We found an early recovery of leukocytes, CD8+ and NK lymphocytes. We also found a trend towards an improved B cell recovery. These results are somewhat in contrast to the altered immune recovery observed in the myeloablative setting. In addition, we found a significant early circulating DC recovery. Circulating blood DCs were also found to be of full donor origin as assessed by FISH in sex-mismatched pairs. Nevertheless, naive CD4 + CD45RA + T cells were found to be profoundly reduced following such regimens.Collectively, these data further enhance the overall benefits of reduced intensity regimens and the need for a stringent biological monitoring for assessment of the potential advantages of reduced intensity allo-BMT in comparison with conventional allo-BMT.

Apoptosis and dysfunction of blood dendritic cells in patients with falciparum and vivax malaria

Acute Plasmodium infections in humans result in dendritic cell dysfunction and apoptosis caused in part by elevated levels of IL-10.

Malaria causes significant morbidity worldwide and a vaccine is urgently required. Plasmodium infection causes considerable immune dysregulation, and elicitation of vaccine immunity remains challenging. Given the central role of dendritic cells (DCs) in initiating immunity, understanding their biology during malaria will improve vaccination outcomes. Circulating DCs are particularly important, as they shape immune responses in vivo and reflect the functional status of other subpopulations. We performed cross-sectional and longitudinal assessments of the frequency, phenotype, and function of circulating DC in 67 Papuan adults during acute uncomplicated P. falciparum, P. vivax, and convalescent P. falciparum infections. We demonstrate that malaria patients display a significant reduction in circulating DC numbers and the concurrent accumulation of immature cells. Such alteration is associated with marked levels of spontaneous apoptosis and impairment in the ability of DC to mature, capture, and present antigens to T cells. Interestingly, sustained levels of plasma IL-10 were observed in patients with acute infection and were implicated in the induction of DC apoptosis. DC apoptosis was reversed upon IL-10 blockade, and DC function recovered when IL-10 levels returned to baseline by convalescence. Our data provide key information on the mechanisms behind DC suppression during malaria and will assist in developing strategies to better harness DC’s immunotherapeutic potential.

Costimulatory molecules on immunogenic versus tolerogenic human dendritic cells

Dendritic cells (DC) are sentinels of immunity, essential for homeostasis of T cell-dependent immune responses. Both functions of DC, initiation of antigen-specific T cell immunity and maintenance of tissue-specific tolerance originate from distinct stages of differentiation, immunogenic versus tolerogenic. Dependent on local micro milieu and inflammatory stimuli, tissue resident immature DC with functional plasticity differentiate into tolerogenic or immunogenic DC with stable phenotypes. They efficiently link innate and adaptive immunity and are ideally positioned to modify T cell-mediated immune responses. Since the T cell stimulatory properties of DC are significantly influenced by their expression of signal II ligands, it is critical to understand the impact of distinct costimulatory pathways on DC function. This review gives an overview of functional different human DC subsets with unique profiles of costimulatory molecules and outlines how different costimulatory pathways together with the immunosuppressive cytokine IL-10 bias immunogenic versus tolerogenic DC functions. Furthermore, we exemplarily describe protocols for the generation of two well-defined monocyte-derived DC subsets for their clinical use, immunogenic versus tolerogenic.

Interleukin-2 and granulocyte-macrophage-colony-stimulating factor immunomodulation with high-dose chemotherapy and autologous hematopoietic stem cell transplantation for patients with metastatic breast cancer

Immunomodulation with cytokines was used to improve the result of high-dose chemotherapy (HDC)/autologous hematopoietic stem cell transplantation (AHST). We examined the use of IL-2 and growth factors for mobilization, ex vivo activation of peripheral blood stem cell (PBSC) and maintenance therapy after HDC/AHST in metastatic breast cancer. Eligible patients with metastatic breast cancer for HDC/AHST were assigned to 1 of 3 protocols for PBSC mobilization: G-CSF (group 1); IL-2 + G-CSF (group 2); or IL-2 + G-CSF + GM-CSF (group 3). HDC with cyclophosphamide, carmustine and thiotepa was given from day -7 to -5. PBSCs were treated ex vivo with IL-2 for 24 h and reinfused on day 0. Maintenance therapy included low-dose IL-2, followed by 2 courses of intermediate-dose IL-2. GM-CSF was given from day 1 until neutrophil recovery. Thirty-four patients (10 in group 1, 14 in group 2, and 10 in group 3) were included. Comparable numbers of CD34(+) cells were collected from all 3 groups; incremental increases of CD3(+) cells were collected from groups 1 to 2 and to 3 (p = 0.03). Major adverse effects from IL-2 were fever, hypotension and fatigue; no treatment-related mortality was seen. At a median follow-up of 790.5 days (range 150-2,722 days), median progression-free survival was 434 days and median overall survival was 1,432 days. Estimated 3-year progression-free and overall survival rates were 31 and 57%. Our study suggested that the use of IL-2 and growth factors immunomodulation with HDC/AHST was feasible with comparable survival rates.

Role of cervical dendritic cell subsets, co-stimulatory molecules, cytokine secretion profile and beta-estradiol in development of sequalae to Chlamydia trachomatis infection

BACKGROUND

Chlamydia trachomatis infection of the female genital tract can lead to serious sequelae resulting in fertility related disorders. Little is known about the mechanism leading to Chlamydia induced pathology and factors responsible for it. As only some of the women develops reproductive disorders while majority of the women clears infection without any severe sequalae, mucosal immune response in women with or without fertility disorders was studied to identify factors which may lead to final clinical outcome of chlamydial infection.

METHODS

Myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) populations in cervical mucosa and peripheral blood were analyzed in controls and Chlamydia positive women with or without fertility disorders with multicoloured flow cytometric analysis. Cervical cytokines (IL-6, IL-8, IL-10, IL-12, TNF-alpha and IFN-gamma), C-reactive protein levels and sex hormone levels in serum were quantified by ELISA.

RESULTS

In cervix of Chlamydia positive women with fertility disorders, significantly high (P < 0.05) numbers of pDCs were present with increased CD80 expression. pDCs correlated significantly with C-reactive protein levels, IL-6 and IFN-gamma levels in women with fertility disorders. In contrast, mDCs showed significant upregulation of CD1a during chlamydial infection and correlated significantly with IL-12 levels in Chlamydia positive fertile women. beta-estradiol levels were significantly higher in women having fertility disorders as compared to fertile women and have significant correlations (r = 0.65; P < 0.05) with pDCs numbers, CD80 expression, IL-6 levels and IFN-gamma levels in these women.

CONCLUSION

These results suggest that development of sequalae in some women can be a result of interplay of many factors including type of dendritic cell, co stimulatory molecule expression, cytokine secretion pattern and hormone levels.

Numerical and functional defects of blood dendritic cells in early- and late-stage breast cancer

The generation of antitumour immunity depends on the nature of dendritic cell (DC)-tumour interactions. These have been studied mostly by using in vitro-derived DC which may not reflect the natural biology of DC in vivo. In breast cancer, only one report has compared blood DC at different stages and no longitudinal evaluation has been performed. Here we conducted three cross-sectional and one one-year longitudinal assessments of blood DC in patients with early (stage I/II, n=137) and advanced (stage IV, n=36) disease compared to healthy controls (n=66). Patients with advanced disease exhibit markedly reduced blood DC counts at diagnosis. Patients with early disease show minimally reduced counts at diagnosis but a prolonged period (1 year) of marked DC suppression after tumour resection. While differing in frequency, DC from both patients with early and advanced disease exhibit reduced expression of CD86 and HLA-DR and decreased immunostimulatory capacities. Finally, by comparing a range of clinically available maturation stimuli, we demonstrate that conditioning with soluble CD40L induces the highest level of maturation and improved T-cell priming. We conclude that although circulating DC are compromised by loco-regional and systemic breast cancer, they respond vigorously to ex vivo conditioning, thus enhancing their immunostimulatory capacity and potential for immunotherapy.

Current approaches in dendritic cell generation and future implications for cancer immunotherapy

The discovery of tumor-associated antigens, which are either selectively or preferentially expressed by tumors, together with an improved insight in dendritic cell biology illustrating their key function in the immune system, have provided a rationale to initiate dendritic cell-based cancer immunotherapy trials. Nevertheless, dendritic cell vaccination is in an early stage, as methods for preparing tumor antigen presenting dendritic cells and improving their immunostimulatory function are continuously being optimized. In addition, recent improvements in immunomonitoring have emphasized the need for careful design of this part of the trials. Still, valuable proofs-of-principle have been obtained, which favor the use of dendritic cells in subsequent, more standardized clinical trials. Here, we review the recent developments in clinical DC generation, antigen loading methods and immunomonitoring approaches for DC-based trials.

Peripheral blood manipulation significantly affects the result of dendritic cell monitoring

It has been postulated that the plasmacytoid/myeloid dendritic cell ratio (pDC/mDC) reflects immune reactivity, and can therefore be used to monitor transplant recipients. We investigated the influence of Ficoll-Paque separation and PBMC cryopreservation on the pDC/mDC ratio and the expression of maturation markers, e.g. chemokine receptors (CKRs) CCR7, CXCR4, and CCR5, in comparison to fresh blood cells. Fractions of pDCs and mDCs, and CKR expression were measured by flow cytometry in fresh blood, in Ficoll-isolated PBMCs and in cryopreserved PBMCs from healthy individuals and kidney transplant recipients. Ficoll-isolation of PBMCs resulted in higher pDC/mDC ratios in both groups compared to fresh blood cells resulting from a relatively large increase in pDCs compared to mDCs. The pDC/mDC ratio increased further after cryopreservation of PBMCs from kidney transplant recipients. Ficoll-isolation and cryopreservation of PBMCs affected the proportion of mDCs and pDCs positive for CKRs, and their expression levels resulting in a more mature phenotype. In conclusion, the pDC/mDC ratio and pDC or mDC maturation status based on CKR expression, is dependent on manipulation of PBMCs. Therefore, fresh blood is preferable for monitoring purposes in transplant patients, as only these cells reflect the in vivo immune-status of patients accurately.

Dendritic cells in autologous hematopoietic stem cell transplantation for diffuse large B-cell lymphoma: graft content and post transplant recovery predict survival

Allograft dendritic cell (DC) content has been identified as a predictor of relapse and event-free survival after allogeneic bone marrow transplantation. However, the prognostic importance of DCs has not been evaluated in the setting of autologous hematopoietic stem cell transplantation (HSCT). We prospectively determined pre-transplant and post transplant DC levels, including DC1 and DC2 subset levels, in 53 patients with diffuse large B-cell non-Hodgkin's lymphoma (DLBC NHL) undergoing autologous HSCT. Pre-transplant DCs were measured in the collected stem cell products and were therefore indicative of cell numbers infused directly into patients; post transplant analysis of DCs was performed on the peripheral blood of patients 6 weeks after the infusion of autologous stem cells. Higher pre-transplant levels of DC1 cells and total DCs were significantly associated with improved survival. Similarly, greater post transplant levels of total DCs and both subsets were significantly associated with survival. These findings suggest a relationship between DC reconstitution and survival following autologous HSCT for DLBC NHL. Strategies to increase autograft DC content or accelerate DC recovery after autologous HSCT might improve outcomes in this setting.

HLA-DR+ immature cells exhibit reduced antigen-presenting cell function but respond to CD40 stimulation

Dendritic cells (DC) have been implicated in the defective function of the immune system during cancer progression. We have demonstrated that patients with cancer have fewer myeloid (CD11c+) and plasmacytoid (CD123(hi)) DC and a concurrent accumulation of CD11c(-)CD123- immature cells expressing HLA-DR (DR(+)IC). Notably, DR(+)IC from cancer patients have a reduced capacity to stimulate allogeneic T-cells. DR(+)IC are also present in healthy donors, albeit in smaller numbers. In this study, we assessed whether DR(+)IC could have an impact on the immune response by comparing their function with DC counterparts. For this purpose, DR(+)IC and DC were purified and tested in the presentation of antigens through major histocompatibility complex (MHC) II and MHC-I molecules. DR(+)IC were less efficient than DC at presenting antigens to T-cells. DR(+)IC induced a limited activation of T-cells, eliciting poor T-helper (Th) 1 and preferentially inducing Th2-biased responses. Importantly, despite DR(+)IC's poor responsiveness to inflammatory factors, in samples from healthy volunteers and breast cancer patients, CD40 ligation induced phenotypic maturation and interleukin 12 secretion, in turn generating more efficient T-cell responses. These data underscore the importance of inefficient antigen presentation as a mechanism for tumor evasion and suggest an approach to improve the efficacy of DC-based immunotherapy for cancer.

A population of HLA-DR+ immature cells accumulates in the blood dendritic cell compartment of patients with different types of cancer

Dendritic cell (DC) defects are an important component of immunosuppression in cancer. Here, we assessed whether cancer could affect circulating DC populations and its correlation with tumor progression. The blood DC compartment was evaluated in 136 patients with breast cancer, prostate cancer, and malignant glioma. Phenotypic, quantitative, and functional analyses were performed at various stages of disease. Patients had significantly fewer circulating myeloid (CD11c+) and plasmacytoid (CD123+) DC, and a concurrent accumulation of CD11c(-)CD123(-) immature cells that expressed high levels of HLA-DR+ immature cells (DR(+)IC). Although DR(+)IC exhibited a limited expression of markers ascribed to mature hematopoietic lineages, expression of HLA-DR, CD40, and CD86 suggested a role as antigen-presenting cells. Nevertheless, DR(+)IC had reduced capacity to capture antigens and elicited poor proliferation and interferon-gamma secretion by T-lymphocytes. Importantly, increased numbers of DR(+)IC correlated with disease status. Patients with metastatic breast cancer showed a larger number of DR(+)IC in the circulation than patients with local/nodal disease. Similarly, in patients with fully resected glioma, the proportion of DR(+)IC in the blood increased when evaluation indicated tumor recurrence. Reduction of blood DC correlating with accumulation of a population of immature cells with poor immunologic function may be associated with increased immunodeficiency observed in cancer.

Numerical and functional assessment of blood dendritic cells in prostate cancer patients

BACKGROUND

Prostate cancer is one of the leading causes of cancer deaths in males and there are currently no effective treatments available for metastatic disease. Although recent clinical trials using dendritic cell (DC) based immunotherapy treatments have demonstrated safety, immunological responses, and some clinical efficacy, better vaccine delivery strategies need to be developed. We have undertaken the first detailed analysis of blood DC (BDC) subsets and their function in prostate cancer patients, with a view to utilizing immunoselected BDC for immunotherapy.

METHODS

We enumerated the CD11c+CD1c+, CD11c+CD16+, and CD11c-CD123+ BDC subsets in whole blood of prostate cancer patients using a single platform TruCOUNT assay. These subsets were identified and purified using flow cytometry and immunomagnetic selection, and their functional capacity analyzed by costimulatory molecule expression, cytokine secretion, and antigen presenting ability.

RESULTS

There were no significant differences in the number or composition of these subsets compared to healthy donors and these cells could be purified with equal efficiency from both groups. The prostate cancer patients BDC had similar levels of key costimulatory molecules and cytokine expression profiles, compared to healthy donors, and these were upregulated to the same extent, in response to exogenous stimuli. BDC from both groups were capable of eliciting allogeneic proliferative responses and inducing autologous CD4+ responses to naïve and recall antigens, and antigen-specific CD8+ responses to influenza matrix protein and prostate specific antigen.

CONCLUSIONS

These results indicate that an immunoselected CD1c+ BDC preparation could provide a suitable vaccine delivery vehicle for future prostate cancer immunotherapy trials.

Impaired circulating myeloid DCs from myeloma patients

BACKGROUND

In clinical trials, cancer patients have received immunotherapy based on DCs generated from leukapheresed blood. It would therefore be an advantage to be able to measure blood levels and estimate the phenotype of DC before leukapheresis, to estimate the yield required for preparation of vaccines, or ex vivo stimulation of T cells for adoptive immunotherapy.

METHODS

Recently, circulating lineage negative (Lin-) myeloid DC cells and their precursors have been identified by flow cytometry. We apply this strategy to the screening of blood samples from patients with multiple myeloma, in an attempt to characterize and quantitate the subset. By a direct flow cytometry approach, the blood levels of circulating lineage (CD3, CD19, CD14) negative, CD33++, HLA-DR+ cells were estimated before and following ex vivo cell differentiation, and phenotyped by MAbs with specificity against HLA-DR, HLA-ABC, CD1a, CD11c, CD33, CD40, CD49d, CD49e, CD54, CD80, CD83, and CD86.

RESULTS

This study demonstrated that multiple myeloma patients have a 50% reduced blood level of Lin-, CD33++, HLA-DR+ myeloid DC, but a DC-precursor level within normal range. Furthermore, GM-CSF and IL-4 ex vivo stimulated DCs demonstrated an impaired up-regulation of the co-stimulatory molecule CD80 and the adhesion molecule CD54.

DISCUSSION

These results may have clinical implications as a predictor for yield and functionality of the harvested DCs to be used in vaccination of myeloma patients.

Dendritic cell subsets in childhood and in children with cancer: relation to age and disease prognosis

Dendritic cells (DC) are a heterogeneous group of uniquely well-equipped bone marrow-derived antigen-presenting cells. They circulate in blood as precursor cells (preDC). In humans, two blood-borne subtypes of preDC can be distinguished by their differential expression of CD11c (CD11c+ preDC; monocytoid DC) and CD123 (CD123+ preDC; plasmacytoid DC). We studied the incidence of monocytoid and plasmacytoid DC in peripheral blood samples from 39 children of various ages (0.4-16.8 years) by flow cytometry, and found a significant negative correlation between the number of plasmacytoid DC and age (r = 0.421, P = 0.012). Monocytoid DC counts did not change significantly with age. Similarly, we analysed DC subsets in 19 children with cancer at the time of diagnosis prior to initiation of any myelosuppressive or antiproliferative treatment and compared the results with those obtained from gender- and age-matched control children. Patients with cancer had significantly less circulating monocytoid DC than controls (medians 13.2 versus 21.4 cells/ micro l, respectively, P = 0.042) at diagnosis, whereas absolute plasmacytoid DC counts did not differ significantly between the study groups. However, clinical outcome of the children with cancer (2.9-5 years follow-up after diagnosis) correlated with plasmacytoid DC count. Children with high plasmacytoid DC counts at diagnosis (above median) survived significantly worse (6/10 deceased) than those with low counts (1/9 deceased) (P = 0.034). Thus, circulating plasmacytoid DC counts are related to age during childhood, and development of cancer is associated with low number of monocytoid DC. A low circulating plasmacytoid DC count at diagnosis was a good prognostic sign.

Monitoring dendritic cells in clinical practice using a new whole blood single-platform TruCOUNT assay

Dendritic cells (DC) from distinct DC subsets are essential contributors to normal human immune responses. Despite this, reliable assays that enable DC to be counted precisely have been slow to evolve. We have now developed a new single-platform flow cytometric assay based on TruCOUNT beads and the whole blood "Lyse/No-Wash" protocol that allows precise counting of the CD14(-) blood DC subsets: CD11c(+)CD16(-) DC, CD11c(+)CD16(+) DC, CD123(hi) DC, CD1c(+) DC and BDCA-3(+) DC. This assay requires 50 microl of whole blood; does not rely on a hematology blood analyser for the absolute DC counts; allows DC counting in EDTA samples 24 h after collection; and is suitable for cord blood and peripheral blood. The data is highly reproducible with intra-assay and inter-assay coefficients of variation less than 3% and 11%, respectively. This assay does not produce the DC-T lymphocyte conjugates that result in DC counting abnormalities in conventional gradient-density separation procedures. Using the TruCOUNT assay, we established that absolute blood DC counts reduce with age in healthy individuals. In preliminary studies, we found a significantly lower absolute blood CD11c(+)CD16(+) DC count in stage III/IV versus stage I/II breast carcinoma patients and a lower absolute blood CD123(hi) DC count in multiple myeloma patients, compared to age-matched controls. These data indicate that scientific progress in DC counting technology will lead to the global standardization of DC counting and allow clinically meaningful data to be obtained.

Increased serum transforming growth factor-beta1 in human colorectal cancer correlates with reduced circulating dendritic cells and increased colonic Langerhans cell infiltration

Cancer-related cytokines may interfere with the differentiation and migration of dendritic cells (DCs) and with the associated up-regulation of co-stimulatory molecules in vitro. We determined whether cytokines affected the distribution and activation of DCs in patients with colorectal cancer by measuring the levels of serum cytokines [transforming growth factor (TGF)-beta1 and vascular endothelial growth factor (VEGF)], DC numbers and phenotype from peripheral blood and mesenteric lymph nodes draining the cancer, and the infiltration of DCs into colorectal cancer. A significant increase in the serum level of TGF-beta1 correlated with a significant reduction in the level of circulating DCs in cancer patients that was associated with an increased infiltration of Langerhans cells into colorectal mucosa. The prevalence but not intensity of co-stimulatory molecule expression in circulating and mesenteric lymph node DCs was reduced in patients with colorectal cancer compared to patients with inflammatory bowel conditions. There was no correlation between co-stimulatory molecule expression and serum TGF-beta1. Thus the circulating DC depletion in colorectal cancer could be explained by a TGF-beta1-related DC redistribution from the circulation into the colorectal cancer and adjacent mucosa where DC levels were increased. There was an impairment of DC activation within colorectal cancer that was not related to serum level of cytokines.

Lack of dendritic cell mobilization into the peripheral blood of cancer patients following standard- or high-dose chemotherapy plus granulocyte-colony stimulating factor

BACKGROUND

Dendritic cells (DC), the most specialized antigen-presenting cells, can be detected in the peripheral blood (PB) and divided into two subsets of populations, DC1 and DC2, endowed with different functions. The aim of this study was to evaluate the effect on DC release and on their subsets of three regimens utilized to mobilize CD34+ cells into the PB in cancer patients and in normal CD34+ cell donors.

PATIENTS AND METHODS

The mobilizing sequences were: standard-dose epirubicin+taxol+granulocyte-colony-stimulating factor (G-CSF; 15 patients with advanced breast cancer), high-dose cyclophosphamide (CTX)+G-CSF (10 patients with breast cancer patients and 7 with non-Hodgkin's lymphoma, NHL), and G-CSF alone (5 normal donors of CD34+ cells for allogeneic transplantation). Comparative data were obtained from the steady-state PB of 20 healthy volunteers. For flow cytometric analysis, DC were gated as negative for specific lineage markers (CD3, CD11b, CD14, CD16, CD56, CD19, CD20, CD34) and positive for HLA-DR. The DC1 and DC2 subsets were defined as CD11c and CDw123 positive, respectively.

RESULTS

The percentages of DC at baseline and the time of CD34+ cell peak were: 0.48 and 0.51 for standard-dose chemotherapy (CT); 0.55 and 0.63 for breast cancer after high-dose CTX+G-CSF; 0.53 and 0.71 for NHL after high-dose CTX+G-CSF; and 0.51 and 0.54 for normal donors of CD34+ cells after G-CSF alone (all p=n.s.). Mean DC1/DC2 ratios in each study group at the time of CD34+ cell peak were 0.10, 0.12, and 0.18, respectively. Finally, in the group of healthy volunteers, the percentage of circulating DC was 0.95 and the mean DC1/DC2 ratio was 1.28.

CONCLUSION

To our knowledge, this is the first report that demonstrates that both standard-dose or high-dose CT, when utilized together with G-CSF, do not induce DC mobilization into the PB, whereas a reversed DC1/DC2 ratio is observed. Furthermore, a lack of significant DC mobilization after G-CSF alone was also seen, in contrast to what was previously observed by others. These data should be taken in account when evaluating clinical correlations between DC number and CPC engraftment in both the transplantation setting, when monitoring the effects on the immune system of combinations of new drugs and/or cytokines, and when high numbers of DC are required for both experimental and clinical applications.

Comparison of monocyte enrichment by immuno-magnetic depletion or adherence for the clinical-scale generation of DC

BACKGROUND

DC generated from monocytes have been used for vaccines. We have developed a monocyte enrichment procedure by depleting T and B cells with anti-CD2 and anti-CD19 Abs using the automated Isolex 300i magnetic cell selector for clinical-scale DC generation in gas permeable SteriCell culture bags. We have also compared DC function, yield and purity of DC generated from adherent monocytes using culture bags in a closed system, with DC generated in conventional tissue culture flasks.

METHODS

Monocytes were enriched from normal donor apheresis products using CD2/19 depletion with experimental software on the Isolex 300i (ISO), adherence (AD) to SteriCell bags and to T175 flasks and then cultured for 7 days in serum-free X-VIVO 15 media with GM-CSF and IL-4. Phenotype and dextran uptake were analyzed by flow cytometry and allogeneic MLR was also evaluated.

RESULTS

ISO-DC and AD-DC from SteriCell bags showed similar viability. Higher purity of ISO-DC than AD-DC was measured by forward- and side-scatter flow cytometry. Similar expression of CD1a, CD80, CD86 and CD83 were observed in both ISO-DC and AD-DC. Similar dextran uptake and allo MLR were also observed.

DISCUSSION

These data indicated that functional DC were generated in gas permeable SteriCell culture bags from both ISO- and AD-monocytes in a closed system.

Mobilization of dendritic cells in cancer patients treated with granulocyte colony-stimulating factor and chemotherapy

The number of dendritic cells (DC) circulating in the peripheral blood of cancer patients were monitored at multiple time points during chemotherapy and granulocyte colony-stimulating factor (G-CSF) support. DC were identified via the lack of expression of standard lineage markers and high expression of HLA-DR (LN-/DR+). The expression of DC-associated markers, including CD83, CD11c, IL-3Ralpha (CDw123) and CD86, within this LN-/DR+ population was also monitored. Maximal mobilization occurred during recovery on d 12, with a mean 32-fold increase in LN-/DR+ numbers. The most striking increase was observed in the LN-/DR+/CD83+ cell population: 12 d after commencement of treatment, the proportion of these cells had increased by approximately 120-fold when compared with baseline. Peripheral blood mononuclear cell (PBMC) and CD34+ cell numbers also peaked 12 d into the treatment regimen in most patients. These data suggest that it should be possible to acquire substantial numbers of DC from leukapheresis products collected from cancer patients undergoing a standard treatment regimen of chemotherapy and G-CSF. This strategy may be a feasible, low-risk means of acquiring cells for DC-based vaccine studies.

Dendritic cell recovery after autologous stem cell transplantation

There is persistent immunosuppression not only in allogeneic but also in autologous stem cell transplantation because humoral and cellular immunity may take a year or more to return to normal, with increased risk of infectious complications. This immune defect may also involve antigen presentation, in particular dendritic cell (DC) function. We evaluated DC subset reconstitution in 58 patients who underwent bone marrow (BM) or peripheral blood (PB) autologous haematopoietic stem cell transplantation (HSCT). In all patients DC type 1 (DC1) and DC type 2 (DC2) were already significantly lower than in normal individuals before conditioning therapy (DC1/microl 3.1 +/- 1.0, DC2/microl 3.0 +/- 1.1). On day 0 and day +7 the mean DC1 and DC2 numbers were very low in both groups. Patients who received unmanipulated marrow or peripheral blood stem cells reached pre-conditioning levels of DC1 and DC2 cells on day +20. In patients receiving selected CD34 cells, DC increased slowly and pre-transplant counts were observed only on day +60. Nearly 'normal' levels of DC1 and DC2 could be observed in the first group from day +180, and were maintained thereafter; in CD34(+) selected patients DC1 and DC2 counts remained lower than normal. Our data emphasise that circulating antigen presenting cells (APC) recover quickly. It remains to be determined if DC frequency in PB reflects their tissue function. The relatively low incidence of infections in patients undergoing autologous transplantation, despite defective lymphocyte reconstitution, could be related to functionally efficient DC.

Generation of large numbers of dendritic cells in a closed system using Cell Factories

There is a growing interest in using dendritic cells (DC) for vaccine approaches in the treatment of cancer and infectious diseases. This requires a reproducible method for the generation of large numbers of DC in a closed culture system suitable for clinical use and conforming to the current guidelines of good manufacturing practices. We designed a system in which the DC were generated in a closed system from adherent monocytes using Cell Factories (DC-CF). Monocytes were enriched from apheresis products by adherence and then cultured in the presence of AB serum or autologous plasma and GM-CSF and IL-4 for 6 days. The DC generated in Cell Factories were extensively compared to research-grade DC generated in conventional tissue culture flasks (DC-TCF). At day 6, the immature DC were harvested and the yield, the viability, the immunophenotype and the functional characteristics of the DC were compared.DC-CF and DC-TCF showed similar viability and purity and scored equally when tested for stability, dextran and latex bead uptake, in MLR and in the activation of influenza-specific memory cells after electroporation with influenza matrix protein 1 (IMP1) mRNA. These data indicated that large numbers of functional clinical-grade DC could be generated from adherent cells in a closed system using Cell Factories.

Immunology of the peritoneal cavity: relevance for host-tumor relation

The peritoneal membrane, formed by a single layer of mesothelial cells, lines the largest cavity of the human body. Anatomic structures of the peritoneal cavity, along with resident leukocyte populations, play an important role in the defense against microorganisms invading by breaching the gut integrity or ascending through the female genital tract. Local immune mechanisms in the peritoneal cavity are also important in patients undergoing peritoneal dialysis and in women with endometriosis. There is now extensive evidence demonstrating the significance of peritoneal immune mechanisms in the control of metastatic spread. Leukocytes belonging to both the innate and adaptive immune systems are present in the peritoneal cavity of normal subjects as well as in patients with intra-abdominal cancer. There is now increased understanding of the mechanisms that not only allow the tumor cells to escape the detection and destruction by the host immune system, but also to use the inflammatory mechanisms to promote tumor growth and spread inside the peritoneal cavity. Malignant ascites represents a model for the study of the interaction between tumor cells and the host immune system as well for the analysis of the tumor microenviroment. The peritoneal immune system may be stimulated by intraperitoneal administration of biologic agents. This peritoneal immunotherapy may be used for palliation of malignant ascites, or as a consolidation strategy in patients with minimal residual disease.

Poor yield of dendritic cell precursors from untreated pediatric cancer

We have studied the generation of dendritic cells (DC) in vitro from healthy children and children with newly diagnosed cancer. Peripheral blood derived adherent cells were harvested and cultured in the presence of granulocyte-macrophage colony-stimulating-factor (GM-CSF) and interleukin-4 (IL-4). Differentiated DC were characterized morphologically and analyzed by flow cytometry and allogenic mixed lymphocyte reaction (MLR). The numbers of adherent cells were two-fold higher in healthy children than in those with malignant tumors: 1.5 x 10(5)/ml of blood (mean) versus 0.7 x 10(5)/ml, respectively (p = 0.025). No significant differences were found in the cell survival or yield after the in vitro cultivation of adherent cells. Cytological examination of cultured cells showed that they were similar to DC in adults, being large, irregularly shaped, with several thin membrane protrusions, and bean-shaped nuclei. Differentiated DC from healthy controls expressed CD86 and HLA-DR, but did not express monocyte markers CD14 and CD64 (FcgammaRI). The phenotype of DC from cancer patients was otherwise similar, except that a substantial proportion (24-85%) continued to express CD64 (p = 0.001). DC derived both from cancer patients and controls were strong stimulators in allogeneic MLR. We conclude that functionally capable DC can be generated in vitro from blood-derived adherent cells in children, but children with untreated cancer yield lower numbers of DC than healthy children. The continued expression of CD64 on DC derived from cancer patients may indicate that adherent cells from cancer patients are more resistant to signals inducing differentiation into DC.

Generation of dendritic cells ex vivo: differences in steady state versus mobilized blood from patients with breast cancer, with lymphoma, and from normal donors

Dendritic cells (DC) are potent antigen-presenting cells that are integral to the initiation of T cell immunity. The ability to culture these cells in vitro has allowed DC immunotherapy to be investigated as a mechanism of enhancing immune responses against various malignancies. We examined the optimal time for generating DC and compared DC generated from normal donors for allogeneic blood stem cell transplantation, or patient's with non-Hodgkin's lymphoma or breast cancer undergoing high-dose chemotherapy and autologous stem cell transplantation. Experiments were conducted to compare DC cultured prior to and post mobilization chemotherapy. Blood was obtained from consenting patients prior to granulocyte colony-stimulating factor (G-CSF) administration with (non-Hodgkin lymphoma and breast cancer) or without (normal donors) chemotherapy. A sample of apheresis product (AP) was obtained at the time of apheresis. DC were generated from peripheral blood mononuclear cells by culturing the adherent cells in the presence of interleukin-4 and granulocyte-macrophage colony-stimulating factor. Resultant DC were harvested and examined for yield, morphology, phenotype, and function. All cell populations yielded highly pure DC, as assessed by light microscopy and flow cytometry. The average cellular yield was significantly greater from AP than steady-state blood in paired and unpaired samples. Yield did not correlate with the percentage of CD14(+) cells, and it negatively correlated with CD34 counts. DC from breast cancer patients functioned significantly better than DC from lymphoma patients in a mixed lymphocyte reaction. These data suggest that the optimal timing of culturing DC is after mobilization, and that differences may exist in the functional capabilities of DC derived from different patient populations.

Malignancy: Changes in Circulating Immature and Mature Dendritic Cells During IL-2 Cancer Immunotherapy and Their Relation with Lymphocyte Increase and Clinical Response

Lymphocytosis is the main biomarker predicting the efficacy of subcutaneous IL-2 anticancer immunotherapy. In addition, it has been demonstrated the fundamental role of dendritic cells (DC) in the generation of an effective anticancer immunity. However, the relation between IL-2 and DC system needs to be further understood. This preliminary study was performed in an attempt to analyze changes in circulating DC during IL-2 cancer immunotherapy in relation to lymphocyte variations and clinical efficacy of treatment. The study included 20 metastatic renal cell cancer patients, who underwent subcutaneous low-dose IL-2 immunotherapy (6.000.000 IU/day for 6 days/week for 4 weeks). To evaluate DC, venous blood samples were collected before and after 2 weeks of IL-2 injections, corresponding to the period of maximum lymphocytosis. Immature (CD123(+) ) and mature (CD11c(+) ) DC were measured by FACS and monoclonal antibodies. IL-2 induced a significant increase in the mean number of circulating mature DC, whereas no substantial change occurred in immature DC mean number. The increase in mature DC was associated with a control of disease, whereas no rise was observed in patients who had progressed on IL-2 immunotherapy. Moreover, the increase in mature DC mean number was significantly higher in patients showing evident lymphocytosis, with lymphocyte enhancement greater than 1000 cells/mmc, than in patients with less pronounced lymphocytosis, even though no significant correlation was seen in between mature DC and lymphocyte increase. This preliminary study would suggest that IL-2 may stimulate DC system and that the clinical anticancer efficacy of IL-2 is associated with the increase in circulating mature DC, which could be considered as a new favourable biomarker during IL-2 immunotherapy.

Activation of Innate Immunity in Nonhuman Primates Following Intraportal Administration of Adenoviral Vectors

The innate immune response to intraportally infused adenoviral vector was evaluated in rhesus monkeys. A first-generation adenovirus-expressing lacZ (Ad-lacZ) was administered at a dose just below that which causes severe morbidity. The response to vector was evaluated for the initial 24 h following infusion. Clinical findings during this time were primarily limited to petechiae, consistent with the development of thrombocytopenia and biochemical evidence of disseminated intravascular coagulation. Serum transaminases were elevated and a lymphopenia developed. Tracking of fluorescent-labeled vector demonstrated distribution to macrophages and dendritic cells of the spleen and Kupffer cells of the liver. A systemic release of the cytokine IL-6 occurred soon after vector infusion. Analysis of splenic cells revealed acute activation of macrophages and dendritic cells followed by massive apoptosis. Bone marrow cultures demonstrated normal erythroid and primitive progenitors with a significant decrease in myeloid progenitors. Similar findings, except the abnormality in bone marrow cultures, were observed in monkeys who received an identical dose of Ad-lacZ in which vector genes were inactivated with psoralen and UV irradiation. These data suggest that inadvertent targeting of antigen-presenting cells following intraportal infusion of vector leads to a systemic cytokine syndrome which may be triggered by the viral capsid proteins.

Inhibition of effects of endogenously synthesized histamine disturbs in vitro human dendritic cell differentiation

Histamine, a principal mediator in various physiological and pathological cell functions is synthesized from L-histidine exclusively by histidine decarboxylase, an enzyme, which is expressed in many tissues of mammalian organism. Histamine plays a role in various cellular functions, including cell differentiation. The aim of this study was to determine the presence and to characterize the role of the endogenously produced histamine during in vitro dendritic cell (DC) differentiation induced by interleukin-4 (IL-4) and granulocyte-monocyte colony stimulating factor (GM-CSF). The changes in intracellular histamine content, biosynthesis and gene expression of histidine decarboxylase were investigated during this process. One also studied how histamine receptor antagonists and a histamine synthesis blocker influence the expression of differentiation antigens on the DC during in vitro maturation. During in vitro differentiation parallel culture incubations were performed by adding H1 receptor antagonist triprolidine, H2 receptor antagonist tiotidine, the tamoxifene derivate DPPE which blocks the intracellular binding of histamine, and an irreversible blocker of histidine decarboxylase, alpha-fluoromethyl histamine (alpha-FMH). The results show simultaneous increase in both histidine decarboxylase level and histamine content during differentiation of elutriated monocytes toward DC. Both blockade of de novo histamine production (by alpha-FMH) and inhibition of histamine binding (by H1 and H2 receptor antagonists, triprolidine and tiotidine, respectively) markedly decreased CD40 expression and that of CD45 from the 3rd day of treatment. DPPE by disturbing intracellular interaction of histamine with cytochrome P-450 moieties was able to decrease the expression of CD45, CD86, HLA-DR, CD33, CD40 and CD11c. Based on the data it is suggested that endogenous histamine is actively synthesized during cytokine-induced in vitro DC differentiation. The functional relevance and autocrine and paracrine action of endogenously produced histamine is supported by the data showing that inhibition of histamine synthesis by HDC, blocking of histamine binding by both 'extracellular' histamine receptors (by specific antagonists, triprolidine and tiotidine) and 'intracellular' antagonists (DPPE) disturb the differentiation of DC. This conclusion is supported by the fact, that by the inhibition of histamine acting in an autocrine/paracrine way, the expression pattern of differentiation markers on DC is markedly changed.

Characteristics of human dendritic cells generated in a microgravity analog culture system

Generation of an effective immune response requires that antigens be processed and presented to T lymphocytes by antigen-presenting cells, the most efficient of which are dendritic cells (DC). Because of their influence on both the innate and the acquired arms of immunity, a defect in DC would be expected to result in a broad impairment of immune function, not unlike that observed in astronauts during or after space flight. In the study reported here, we investigated whether DC generation and function are altered in a culture environment that models microgravity, i.e., the rotary-cell culture system (RCCS). We observed that RCCS supported the generation of DC identified by morphology, phenotype (HLA-DR+ and lacking lineage-associated markers), and function (high allostimulatory activity). However, the yield of DC from RCCS was significantly lower than that from static cultures. RCCS-generated DC were less able to phagocytose Aspergillus fumigatus conidia and expressed a lower density of surface HLA-DR. The proportion of DC expressing CD80 was also significantly reduced in RCCS compared to static cultures. When exposed to fungal antigens, RCCS-generated DC produced lower levels of interleukin-12 and failed to upregulate some costimulatory/adhesion molecules involved in antigen presentation. These data suggest that DC generation, and some functions needed to mount an effective immune response to pathogens, may be disturbed in the microgravity environment of space.

Dendritic cell-mediated stimulation of the in vitro lymphocyte response to Aspergillus

Lymphocytes play a major role in host defense against Aspergillus, but little is known about the contribution of dendritic cells (DC) to antifungal immunity in humans. We have observed that DC derived from normal volunteers phagocytose heat-killed A. fumigatus conidia. Following 24 h of exposure to the fungus, DC displayed an increase in the mean fluorescence intensity of HLA-DR, CD80, and CD86, and an increase in the percentage of CD54(+) cells. These DC also displayed increased production of IL-12. DC derived from CD34(+) progenitors or monocytes stimulated autologous lymphocytes to proliferate and produce high levels of interferon-gamma, but not interleukin-10, in response to fungal antigen. DC generated from CD34(+) progenitors collected prior to autologous or allogeneic stem cell transplantation also partially restored the in vitro antifungal proliferative response of lymphocytes obtained from patients 1 month after transplantation. These results suggest that DC are important to host-response to A. fumigatus, and that ex vivo-generated DC might be useful in restoring or enhancing the antifungal immunity after hematopoietic stem cell transplantation.

Dysfunctional regulation of the development of monocyte-derived dendritic cells in cancer patients

Dendritic cells (DCs) are highly effective antigen (Ag)-presenting cells (APCs) that are required for the initiation of the immune response. DCs derived from cancer patients have been shown to be defective in several phenotypic and functional properties. However, little is known about the capacity of monocytes derived from cancer patients to differentiate into DCs. Herein, we examined the differentiation of monocyte-derived DCs in cancer patients. Flow cytometric analysis revealed that monocytes derived from cancer patients cultured with granulocyte-macrophage colony-stimulating factor (GM-CSF) plus interleukin-4 (IL-4) exhibited lower levels of CD11c, CD40, CD86, and HLA-DR expression as compared with those of monocyte-derived DCs from healthy volunteers. Furthermore, the capacities of DCs derived from cancer patients' monocytes to stimulate allogeneic T cell responses and to migrate in response to regulated-on-activation normal T cells expressed and secreted (RANTES) were impaired in comparison with those of monocyte-derived DCs from healthy volunteers. However, the two cell types had similar pinocytotic capacities for fluorescein isothiocyanate labeled-dextran (FITC-DX) and lucifer yellow (LY). These results suggest that monocytes from cancer patients may be defective in the capacity to develop into DCs.

Recovery of lymphocyte and dendritic cell subsets after autologous CD34+ cell transplantation

Following high-dose chemotherapy (HDC) and peripheral blood progenitor cell transplantation (PBPCT), there are profound changes in leukocyte homeostasis and the immune system is compromised. Transplantation of purified CD34+ cells may further compromise immune recovery because the grafts are depleted of mature immune cells. However, a detailed monitoring of immune cell reconstitution has not been done. We monitored blood levels of antigen-presenting cells (APC) and of lymphocytes by multi-color flow cytometry at different times post CD34+ PBPCT. We found a rapid normalization of circulating levels of the antigen-presenting CD11c+ dendritic cells (defined as lineage- HLA-DR+ CD11c+ cells). There was a slight over-representation of lin- DR+ CD11c- cells at day 42 post transplantation suggesting that the composition of the APC population might be affected. Normal levels of total T, B and NK lymphocytes were rapidly achieved but the composition of the T cell population was abnormal. Patients had elevated levels of CD8+ T cells at early times and a persistent reduction in levels of naive CD8+ T cells (CD8+ CD4- CD45RA+ CD27+) and of naive CD4+ T cells (CD4+CD3+ CD8- CD45RA+). Thus, we found a rapid recovery of DC after CD34+ PBPCT but the specific numerical defects in naive T cells are likely to be a major cause of immune dysfunction in the patients. Bone Marrow Transplantation (2000) 25, 1249-1255.

Simplified quantitation of myeloid dendritic cells in peripheral blood using flow cytometry

BACKGROUND

Recognition of the importance of dendritic cells (DC) in the initiation of T-cell-dependent immune responses has led to increasing interest in methods for the identification of DC within the circulation. We sought to develop a flow cytometric method that would allow the reliable enumeration of absolute myeloid DC counts in minimally manipulated blood samples.

METHODS

Myeloid DC were identified by three-color staining of whole blood leukocytes as a discrete population of mononuclear cells expressing high levels of HLA-DR and CD33, yet having little or no expression of CD14 and CD16. This method was analyzed for reproducibility and variation in blood DC number during typical clinical day hours and after exercise. The new method was compared to an established commercial kit method.

RESULTS

FACS sorting of the CD33(+) DC showed that they morphologically resembled immature DC, and developed cytoplasmic projections typical of mature DC following overnight culture in granulocyte macrophage-colony stimulating factor (GM-CSF). Within peripheral blood, these DC were found at a mean concentration of 17. 4 +/- 5.4 x 10(6) per liter, corresponding to 0.93 +/- 0.27% of mononuclear cells. Comparison of duplicate samples stained and analyzed in parallel showed that the intrasample variability was very low, with an intraclass correlation coefficient of 0.95. The frequency of CD33(+) myeloid DC and their light scatter characteristics were similar to that of CD11c(+) myeloid cells. Four-color FACS analysis revealed complete identity of CD11c(hi), HLA-DR(+) DC with CD33(+), HLA-DR(+) DC. Only rare CD33(+) DC coexpressed CD123 and HLA-DR. Numbers of blood myeloid DC, identified by CD33 staining, showed no significant variation during standard laboratory hours. However, their numbers rose significantly during vigorous exercise, in parallel to other blood cells.

CONCLUSIONS

The method described herein is rapid, reproducible, requires only small volumes of blood, can be readily used by a clinical immunology laboratory, and requires fewer antibodies than a currently available commercial method.

Simplified quantitation of myeloid dendritic cells in peripheral blood using flow cytometry

BACKGROUND

Recognition of the importance of dendritic cells (DC) in the initiation of T-cell-dependent immune responses has led to increasing interest in methods for the identification of DC within the circulation. We sought to develop a flow cytometric method that would allow the reliable enumeration of absolute myeloid DC counts in minimally manipulated blood samples.

METHODS

Myeloid DC were identified by three-color staining of whole blood leukocytes as a discrete population of mononuclear cells expressing high levels of HLA-DR and CD33, yet having little or no expression of CD14 and CD16. This method was analyzed for reproducibility and variation in blood DC number during typical clinical day hours and after exercise. The new method was compared to an established commercial kit method.

RESULTS

FACS sorting of the CD33(+) DC showed that they morphologically resembled immature DC, and developed cytoplasmic projections typical of mature DC following overnight culture in granulocyte macrophage-colony stimulating factor (GM-CSF). Within peripheral blood, these DC were found at a mean concentration of 17. 4 +/- 5.4 x 10(6) per liter, corresponding to 0.93 +/- 0.27% of mononuclear cells. Comparison of duplicate samples stained and analyzed in parallel showed that the intrasample variability was very low, with an intraclass correlation coefficient of 0.95. The frequency of CD33(+) myeloid DC and their light scatter characteristics were similar to that of CD11c(+) myeloid cells. Four-color FACS analysis revealed complete identity of CD11c(hi), HLA-DR(+) DC with CD33(+), HLA-DR(+) DC. Only rare CD33(+) DC coexpressed CD123 and HLA-DR. Numbers of blood myeloid DC, identified by CD33 staining, showed no significant variation during standard laboratory hours. However, their numbers rose significantly during vigorous exercise, in parallel to other blood cells.

CONCLUSIONS

The method described herein is rapid, reproducible, requires only small volumes of blood, can be readily used by a clinical immunology laboratory, and requires fewer antibodies than a currently available commercial method.

Dendritic cell-derived nitric oxide is involved in IL-4-induced suppression of experimental allergic encephalomyelitis (EAE) in Lewis rats

Cytokines play a crucial role in initiating and perpetuating EAE, an animal model of multiple sclerosis (MS). A low dose of IL-4, administered by the nasal route over 5 days (100 ng/rat per day) prior to immunization, improved clinical scores of EAE induced in Lewis rats with myelin basic protein (MBP) peptide 68-86 (MBP 68-86). We examined whether dendritic cells (DC) may have contributed to the amelioration of the disease process. These professional antigen-presenting cells (APC) not only activate T cells, but also tolerize T cells to antigens, thereby minimizing autoimmune reactions. We found that IL-4 administration enhanced proliferation of DC. In comparison with DC of PBS-treated rats, DC from IL-4-treated rats secreted high levels of interferon-gamma (IFN-gamma) and IL-10. Nitric oxide (NO) production by DC was also strongly augmented in IL-4-treated rats. In vitro studies showed that IL-4 stimulated DC expansion and that IFN-gamma enhanced NO production by DC. DC-derived NO promoted apoptosis of autoreactive T cells. These results indicate that nasal administration of IL-4 promotes activation of DC and induces production of IFN-gamma and IL-10 by DC. IL-10 suppresses antigen presentation by DC, while IFN-gamma induces NO production by DC which leads to apoptosis in autoreactive T cells. Such a DC-derived negative feedback loop might contribute to the clinical improvement observed in EAE.

Mechanisms of recovery from experimental allergic encephalomyelitis induced with myelin basic protein peptide 68-86 in Lewis rats: a role for dendritic cells in inducing apoptosis of CD4+ T cells

Spontaneous remission of experimental allergic encephalomyelitis (EAE) is usually associated with prominent apoptosis. The mechanisms behind apoptosis are unknown. We examined the functions of dendritic cells (DC) from Lewis rats with EAE induced by immunization with myelin basic protein peptide 68-86 (MBP68 - - 86). Recovery from EAE was associated with three major functional changes of freshly prepared DC: (1) elevated proliferation, (2) increased nitric oxide (NO) production, and (3) augmented IFN-gamma secretion. In Freund's complete adjuvant (FCA)-immunized control rats, no increase of proliferation, NO production or IFN-gamma secretion was observed on day 21 post-immunization (p.i.), i.e., recovery from EAE. In vitro effects of IFN-gamma, TNF-alpha, TGF-beta1, IL-4 and IL-10 on DC were examined. IFN-gamma enhanced proliferation and NO production by DC, while TNF-alpha and IL-4 induced only slight DC proliferation. DC from recovering EAE rats (day 21 p.i.) suppressed MBP68 - - 86-induced T cell proliferation compared to DC obtained at other time points in EAE and FCA-immunized rats. DC-derived NO induced apoptosis of CD4+ T cells, thereby inhibiting autoreactive T cell responses. Besides IFN-gamma stimulation, NO production by DC was mainly induced in an antigen-dependent manner when DC were co-cultured with T cells. The results suggest that spontaneous recovery from EAE is associated with augmented DC functions. Overproduction of NO by DC results in apoptosis of autoreactive CD4+ T cells, thereby decreasing autoreactive T cell reactivities. The existence of such a NO negative feedback loop may contribute to remission of EAE.