Distinct epitope structures of defensin-like proteins linked to proline-rich regions give rise to differences in their allergenic activity.

BACKGROUND: Art v 1, Amb a 4, and Par h 1 are allergenic defensin-polyproline-linked proteins present in mugwort, ragweed, and feverfew pollen, respectively. We aimed to investigate the physicochemical and immunological features underlying the different allergenic capacities of those allergens. METHODS: Recombinant defensin-polyproline-linked proteins were expressed in E. coli and physicochemically characterized in detail regarding identity, secondary structure, and aggregation status. Allergenic activity was assessed by mediator releases assay, serum IgE reactivity, and IgE inhibition ELISA using sera of patients from Austria, Canada, and Korea. Endolysosomal protein degradation and T-cell cross-reactivity were studied in vitro. RESULTS: Despite variations in the proline-rich region, similar secondary structure elements were observed in the defensin-like domains. Seventy-four percent and 52% of the Austrian and Canadian patients reacted to all three allergens, while Korean patients were almost exclusively sensitized to Art v 1. This was reflected by IgE inhibition assays demonstrating high cross-reactivity for Austrian, medium for Canadian, and low for Korean sera. In a subgroup of patients, IgE reactivity toward structurally altered Amb a 4 and Par h 1 was not changed suggesting involvement of linear epitopes. Immunologically relevant endolysosomal stability of the defensin-like domain was limited to Art v 1 and no T-cell cross-reactivity with Art v 125-36 was observed. CONCLUSIONS: Despite structural similarity, different IgE-binding profiles and proteolytic processing impacted the allergenic capacity of defensin-polyproline-linked molecules. Based on the fact that Amb a 4 demonstrated distinct IgE-binding epitopes, we suggest inclusion in molecule-based allergy diagnosis.

Blocking antibodies induced by allergen-specific immunotherapy ameliorate allergic airway disease in a human/mouse chimeric model.

BACKGROUND: Allergen-specific immunotherapy (AIT) induces specific blocking antibodies (Ab), which are claimed to prevent IgE-mediated reactions to allergens. Additionally, AIT modulates cellular responses to allergens, for example, by desensitizing effector cells, inducing regulatory T and B lymphocytes and immune deviation. It is still enigmatic which of these mechanisms mediate(s) clinical tolerance. We sought to address the role of AIT-induced blocking Ab separately from cellular responses in a chimeric human/mouse model of respiratory allergy. METHODS: Nonobese diabetic severe combined immunodeficient γc-/- (NSG) mice received intraperitoneally allergen-reactive PBMC from birch pollen-allergic patients together with birch pollen extract and human IL-4. Engraftment was assessed by flow cytometry. Airway hyperresponsiveness (AHR) and bronchial inflammation were analyzed after intranasal challenges with allergen or PBS. Sera collected from patients before and during AIT with birch pollen were added to the allergen prior to intranasal challenge. The IgE-blocking activity of post-AIT sera was assessed in vitro. RESULTS: Human cells were detected in cell suspensions of murine lungs and spleens indicating successful humanization. Humanized mice displayed a more pronounced AHR and bronchial inflammation when challenged with allergen compared to negative controls. Post-AIT sera exerted IgE-blocking activity. In contrast to pre-AIT sera, the presence of heterologous and autologous post-AIT sera significantly reduced the allergic airway inflammation and matched their IgE-blocking activity determined in vitro. CONCLUSION: Our data demonstrate that post-AIT sera with IgE-blocking activity ameliorate allergic airway inflammation in a human/mouse chimeric model of respiratory allergy independently of AIT-induced cellular changes.

Rapid decline in insulin antibodies and glutamic acid decarboxylase autoantibodies with ibrutinib therapy of chronic lymphocytic leukaemia.

WHAT IS KNOWN AND OBJECTIVE: Ibrutinib is inhibiting the Bruton's tyrosine kinase (BTK), thereby influencing B-cell development. We describe an unexpected side effect of ibrutinib in two patients with chronic lymphocytic leukaemia concerning the vigorous decrease of two different diabetes-associated antibodies. CASE DESCRIPTION: Two weeks after onset of ibrutinib therapy, patient A frequently noticed symptoms of hypoglycaemia such as dizziness and blurred vision. Blood glucose declined to 35-40 mg/dL. He had to lower his insulin dose step by step. High levels of insulin antibodies which had developed during insulin therapy were detected. Seven weeks after start of ibrutinib, his insulin antibodies level had dropped by 54.6%. Patient B had a 54.1% decrease in his glutamic acid decarboxylase autoantibodies level after 7 weeks. WHAT IS NEW AND CONCLUSION: The inhibitory effect of ibrutinib on the levels of insulin antibodies and glutamic acid decarboxylase autoantibodies is a novel finding and may have implications for diabetes care.

HLA class II peptide tetramers vs allergen-induced proliferation for identification of allergen-specific CD4 T cells.

BACKGROUND: Fluorescence-labeled MHC class II/peptide tetramer complexes are considered as optimal tools to characterize allergen-specific CD4(+) T cells, but this technique is restricted to frequently expressed HLA class II molecules and knowledge of immunodominant epitopes. In contrast, allergen-stimulated proliferation assessed by CFSE dilution is less sophisticated and widely applicable. The major mugwort allergen, Art v 1, contains only one single, immunodominant, HLA-DR1-restricted epitope (Art v 125-36 ). Thus, essentially all Art v 1-reactive cells should be identified by a HLA-DRB1*01:01/Art v 119-36 tetramer. METHODS: We compared specificity and sensitivity of tetramer(+) and allergen-induced proliferating (CFSE(lo) ) CD4(+) T cells by flow cytometry. RESULTS: The frequency of tetramer(+) CD4(+) T cells determined ex vivo in PBMC of mugwort-allergic individuals ranged from 0 to 0.029%. After 2-3 weeks of in vitro expansion, sufficient tetramer(+) T cells for phenotyping were detected in 83% of Art v 125-36 -reactive T-cell lines (TCL) from mugwort-allergic individuals, but not in TCL from healthy individuals. The tetramers defined bona fide Th2 cells. Notably, Art v 125-36 -reactive TCL depleted of tetramer(+) T cells still reacted to the peptide, and only 44% of Art v 125-36 -specific T-cell clones were detected by the tetramer. CFSE(lo) CD4(+) T cells contained only 0.3-10.7% of tetramer(+) T cells and very low proportions of Th2 cells. CONCLUSION: Allergen-specific T cells can be identified by HLA class II tetramers with high specificity, but unexpected low sensitivity. In contrast, allergen-stimulated CFSE(lo) CD4(+) T cells contain extremely high fractions of bystander cells. Therefore, for T-cell monitoring, either method should be interpreted with caution.

Azithromycin suppresses CD4(+) T-cell activation by direct modulation of mTOR activity.

Advanced macrolides, such as azithromycin (AZM) or clarithromycin (CLM), are antibiotics with immunomodulatory properties. Here we have sought to evaluate their in vitro influence on the activation of CD4(+) T-cells. Isolated CD4(+) T-cells were stimulated with agonistic anti-CD3/anti-CD28 monoclonal antibodies in the presence of 0.6 mg/L, 2.5 mg/L, 10 mg/L or 40 mg/L AZM or CLM. Cell proliferation, cytokine level in supernatants and cell viability was assessed. Intracellular signaling pathways were evaluated using reporter cell lines, FACS analysis, immunoblotting and in vitro kinase assays. AZM inhibited cell proliferation rate and cytokine secretion of CD4(+) T-cells in a dose-dependent manner. Similarly, high concentrations of CLM (40 mg/L) also suppressed these T-cell functions. Analysis of molecular signaling pathways revealed that exposure to AZM reduced the phosphorylation of the S6 ribosomal protein, a downstream target of mTOR. This effect was also observed at 40 mg/L CLM. In vitro kinase studies using recombinant mTOR showed that AZM inhibited mTOR activity. In contrast to rapamycin, this inhibition was independent of FKBP12. We show for the first time that AZM and to a lesser extent CLM act as immunosuppressive agents on CD4(+) T-cells by inhibiting mTOR activity. Our results might have implications for the clinical use of macrolides.

Whole-heart cine MRI in a single breath-hold--a compressed sensing accelerated 3D acquisition technique for assessment of cardiac function.

PURPOSE: The aim of this study was to perform functional MR imaging of the whole heart in a single breath-hold using an undersampled 3 D trajectory for data acquisition in combination with compressed sensing for image reconstruction. MATERIALS AND METHODS: Measurements were performed using an SSFP sequence on a 3 T whole-body system equipped with a 32-channel body array coil. A 3 D radial stack-of-stars sampling scheme was utilized enabling efficient undersampling of the k-space and thereby accelerating data acquisition. Compressed sensing was applied for the reconstruction of the missing data. A validation study was performed based on a fully sampled dataset acquired by standard Cartesian cine imaging of 2 D slices on a healthy volunteer. The results were investigated with regard to systematic errors and resolution losses possibly introduced by the developed reconstruction. Subsequently, the proposed technique was applied for in-vivo functional cardiac imaging of the whole heart in a single breath-hold of 27  s. The developed technique was tested on three healthy volunteers to examine its reproducibility. RESULTS: By means of the results of the simulation (temporal resolution: 47  ms, spatial resolution: 1.4 × 1.4 × 8  mm, 3 D image matrix: 208 × 208 × 10), an overall acceleration factor of 10 has been found where the compressed sensing reconstructed image series shows only very low systematic errors and a slight in-plane resolution loss of 15 %. The results of the in-vivo study (temporal resolution: 40.5  ms, spatial resolution: 2.1 × 2.1 × 8  mm, 3 D image matrix: 224 × 224 × 12) performed with an acceleration factor of 10.7 confirm the overall good image quality of the presented technique for undersampled acquisitions. CONCLUSION: The combination of 3 D radial data acquisition and model-based compressed sensing reconstruction allows high acceleration factors enabling cardiac functional imaging of the whole heart within only one breath-hold. The image quality in the simulated dataset and the in-vivo measurement highlights the great potential of the presented technique for an efficient assessment of cardiac functional parameters.

NI-1: a novel canine mastocytoma model for studying drug resistance and IgER-dependent mast cell activation.

BACKGROUND: Advanced mast cell (MC) disorders are characterized by uncontrolled growth of neoplastic MC in various organs, mediator-related symptoms, and a poor prognosis. Kit mutations supposedly contribute to abnormal growth and drug resistance in these patients. METHODS: We established a novel canine mastocytoma cell line, NI-1, from a patient suffering from MC leukemia. RESULTS: NI-1 cells were found to form mastocytoma lesions in NOD/SCID IL-2Rgamma(null) mice and to harbor several homozygous Kit mutations, including missense mutations at nucleotides 107(C→T) and 1187(A→G), a 12-bp duplication (nucleotide 1263), and a 12-bp deletion (nucleotide 1550). NI-1 cells expressed several MC differentiation antigens, including tryptase, Kit, and a functional IgE receptor. Compared to the C2 mastocytoma cell line harboring a Kit exon 11 mutation, NI-1 cells were found to be less responsive against the Kit tyrosine kinase inhibitors (TKI) masitinib and imatinib, but were even more sensitive against proliferation-inhibitory effects of the mammalian target of rapamycin (mTOR) blocker RAD001 and PI3-kinase/mTOR blocker NVP-BEZ235. The Kit-targeting multikinase inhibitors PKC412 and dasatinib were also found to override TKI resistance in NI-1 cells, and produced growth inhibition with reasonable IC(50) values (<0.1 µM). CONCLUSION: NI-1 may serve as a useful tool to investigate IgE-dependent reactions and mechanisms of abnormal growth and drug resistance in neoplastic MC in advanced mastocytosis.

The Hsp32 inhibitors SMA-ZnPP and PEG-ZnPP exert major growth-inhibitory effects on D34+/CD38+ and CD34+/CD38- AML progenitor cells.

Heat shock protein 32 (Hsp32), also known as heme oxygenase 1 (HO-1), has recently been identified as a potential target in various hematologic malignancies. We provide evidence that Hsp32 is constitutively expressed in primary leukemic cells in patients with acute myeloid leukemia (AML) and in various AML cell lines (HL60, U937, KG1). Expression of Hsp32 mRNA was demonstrable by qPCR, and expression of the Hsp32 protein by immunocytochemistry and Western blotting. The stem cell-enriched CD34+/CD38+ and CD34+/CD38- fractions of AML cells were found to express Hsp32 mRNA in excess over normal CD34+ progenitor cells. Two Hsp32-targeting drugs, pegylated zinc-protoporphyrin (PEG-ZnPP) and styrene-maleic-acid-copolymer-micelle-encapsulated ZnPP (SMAZnPP), were found to inhibit cytokine-dependent and spontaneous proliferation in all 3 AML cell lines as well as in primary AML cells. Growth inhibitory effects of SMA-ZnPP and PEG-ZnPP were dose-dependent with IC50 values ranging between 1 and 20 µM, and were accompanied by apoptosis as evidenced by light- and electron microscopy, Tunel assay, and caspase-3 activation. Finally, we were able to demonstrate that SMA-ZnPP inhibits cytokine-dependent proliferation of CD34+/CD38+ and CD34+/CD38- AML progenitor cells in vitro in all patients as well as leukemiainitiation of AML stem cells in NOD-SCID IL-2Rγ(-/-) (NSG) mice in vivo. Together, our data suggest that Hsp32 plays an important role as a survival factor in leukemic stem cells and as a potential new target in AML.

Danon disease: case report and detection of new mutation.

Danon disease is an X-linked disorder resulting from mutations in the lysosome-associated membrane protein-2 (LAMP2) gene. We report a male patient with skeletal myopathy, mental retardation, and massive hypertrophic obstructive cardiomyopathy necessitating heart transplantation. Immunohistochemistry of skeletal muscle and leukocytes, western blot analysis of leukocytes and cardiac muscle, flow cytometry, and DNA sequencing were performed. Muscle biopsy revealed autophagic vacuolar myopathy and lack of immunohistochemically detectable LAMP-2. Diagnosis of Danon disease was confirmed by western blot analysis of myocardial tissue and peripheral blood sample of the patient showing deficiency of LAMP-2 in myocardium and leukocytes. Moreover, absence of LAMP-2 in lymphocytes, monocytes and granulocytes was shown by flow cytometric analysis. Genetic analysis of the LAMP2 gene revealed a novel 1-bp deletion at position 179 (c.179delC) at the 3' end of exon 2, resulting in a frameshift with a premature stop codon.

Targeting of Hsp32 in solid tumors and leukemias: a novel approach to optimize anticancer therapy.

Heat shock protein 32 (Hsp32), also known as heme oxygenase-1 (HO-1), is a stress-related anti-apoptotic molecule, that has been implicated in enhanced survival of neoplastic cells and in drug-resistance. We here show that Hsp32 is expressed in most solid tumors and hematopoietic neoplasms and may be employed as a new therapeutic target as evidenced by experiments using specific siRNA and a Hsp32-targeting pharmacologic inhibitor. This Hsp-32 targeting drug, SMA-ZnPP, was found to inhibit the proliferation of neoplastic cells with IC(50) values ranging between 1 and 50 microM. In addition, SMA-ZnPP induced apoptosis in all neoplastic cells examined. Furthermore, SMA-ZnPP was found to synergize with other targeted and conventional drugs in producing growth-inhibition. Resulting synergistic effects were observed in all tumor and leukemia cells examined. Interestingly, several of the drug partners, when applied as single agents, induced the expression of Hsp32 in neoplastic cells, suggesting that synergistic effects resulted from SMA-ZnPP-induced ablation of a Hsp32-mediated survival-pathway that is otherwise used by tumor cells to escape drug-induced apoptosis. Together, Hsp32 is an important survival factor and target in solid tumors and hematopoietic neoplasms, and may be used to optimize anticancer therapy by combining conventional or targeted drugs with Hsp32-inhibitors. Based on these data, it seems desirable to explore the value of Hsp32-targeting drugs as anti-cancer agents in clinical trials.

Targeting of mTOR is associated with decreased growth and decreased VEGF expression in acute myeloid leukaemia cells.

BACKGROUND: The mammalian target of rapamycin (mTOR) has recently been implicated in leukaemic cell growth, tumour-associated angiogenesis and expression of vascular endothelial growth factor (VEGF). We examined whether mTOR plays a role as regulator of growth and VEGF-expression in acute myeloid leukaemia (AML). Three mTOR-targeting drugs, rapamycin, everolimus (RAD001) and CCI-779, were applied. The effects of these drugs on growth, survival, apoptosis and VEGF expression in primary AML cells and various AML cell lines were examined. MATERIALS AND METHODS: Growth of AML cells and AML-derived cell lines was assessed by (3)H-thymidine incorporation, survival was examined by light- and electron microscopy, by Tunel assay and by AnnexinV-staining, and the expression of VEGF by Northern blotting, RT-PCR and ELISA. RESULTS: Rapamycin was found to counteract growth in the AML cell lines U937 and KG1a as well as in primary AML cells in 14/18 patients examined. The effects of rapamycin and its derivatives were dose-dependent (IC(50): 10 pM-100 nM). It was also found that exposure to mTOR-targeting drugs resulted in apoptosis and in decreased expression of VEGF in leukaemic cells. CONCLUSIONS: mTOR-targeting drugs exert antileukaemic effects on AML cells in vitro through multiple actions, including direct inhibition of proliferation, induction of apoptosis and suppression of VEGF. Based on this study and other studies, mTOR can be regarded as a potential drug target in AML.

Evaluation of antileukaemic effects of rapamycin in patients with imatinib-resistant chronic myeloid leukaemia.

BACKGROUND: Recent data suggest that the mammalian target of rapamycin (mTOR) is involved in the regulation of growth of neoplastic cells in chronic myeloid leukaemia (CML). PATIENTS AND METHODS: We treated six patients with imatinib-resistant CML in haematological relapse (leukocytes > 20,000 microL(-1)) with rapamycin at 2 mg per os daily for 14 consecutive days, with dose-adjustment allowed to reach a target rapamycin serum concentration of 10-20 pg mL(-1). RESULTS: A major leukocyte response with decrease to less than 10,000 microL(-1) was obtained in two patients, and a minor transient response was seen in two other patients. In responding patients, we also observed a decrease in vascular endothelial growth factor (VEGF) mRNA levels in circulating leukaemic cells. Side effects during rapamycin treatment were mild in most patients. In one patient, pneumonia developed. Rapamycin was also found to counteract growth of CML cells in vitro as determined by (3)H-thymidine incorporation. Moreover, rapamycin inhibited the growth of Ba/F3 cells exhibiting various imatinib-resistant mutants of BCR/ABL, including the T315I variant that exhibits resistance against most currently available BCR/ABL kinase inhibitors. CONCLUSIONS: Rapamycin shows antileukaemic effects in imatinib-resistant CML in vitro and in vivo. Larger trials with rapamycin or rapamycin-derivatives in combination with other targeted drugs are warranted to further determine clinical efficacy in CML.

Deregulated expression of fat and muscle genes in B-cell chronic lymphocytic leukemia with high lipoprotein lipase expression.

Lipoprotein lipase (LPL) is a prognostic marker in B-cell chronic lymphocytic leukemia (B-CLL) related to immunoglobulin V(H) gene (IgV(H))mutational status. We determined gene expression profiles using Affymetrix U133A GeneChips in two groups of B-CLLs selected for either high ('LPL+', n=10) or low ('LPL-', n=10) LPL mRNA expression. Selected genes were verified by real-time PCR in an extended patient cohort (n=42). A total of 111 genes discriminated LPL+ from LPL- B-CLLs. Of these, the top three genes associated with time to first treatment were Septin10, DMD and Gravin (P

Lipid rafts and pseudotyping.

Specific interactions between envelope and core proteins govern the membrane assembly of most enveloped viruses. Despite this, mixed infections lead to pseudotyping, the association of the viral cores of one virus with the envelopes of another. How does this occur? We show here that the detergent-insoluble lipid rafts of the plasma membrane function as a natural meeting point for the transmembrane and core components of a phylogenetically diverse collection of enveloped viruses. As a result, viral particles preferentially incorporate both the envelope components of other viruses as well as the extra- and intracellular constituents of host cell lipid rafts, including gangliosides, glycosyl phosphatidylinositol-anchored surface proteins, and intracellular signal transduction molecules. Pharmacological disruption of lipid rafts interferes with virus production.

Dendritic Cell Generation from Highly Purified CD14+Monocytes.

Dendritic cells (DC) play a pivotal role in the function of the immune system, for they are the primary antigen-presenting cells (APC) in the activation of naive T-lymphocyte responses (1). Recent studies have uncovered complexity in the DC lineage with several subsets, functions, and maturational stages. Although it is generally accepted that human DC derive from hematopoietic progenitor cells (2-9), it is not clear at present whether DC cells and their precursors represent a separate hematopoietic lineage or whether DC should be seen as specialized macrophages with particular morphological, molecular, and functional features. Several lines of evidence point to DC and monocytes/ macrophages being offspring of the same CD34(+) hematopoietic progenitor cell (3-5,12-14, and reviewed in ([10,11].) DC committed precursor cells have also been identified in peripheral blood (15-18).

CD99 engagement on human peripheral blood T cells results in TCR/CD3-dependent cellular activation and allows for Th1-restricted cytokine production.

We have assessed the functional effect of CD99 engagement on resting human peripheral blood (PB) T cells. CD99, as detected by the mAb 3B2/TA8, is constitutively expressed on all PB T cells and becomes further up-regulated upon cellular activation. In this study we demonstrate that cross-linking of the CD99 molecule with the agonistic mAb 3B2/TA8 cooperates with suboptimal TCR/CD3 signals, but not with phorbol ester, ionomycin, or CD28 mAb stimulation, to induce proliferation of resting PB T cells. Comparable stimulatory effects were observed with the CD99 mAb 12E7. Characterization of the signaling pathways involved revealed that CD99 engagement leads to the elevation of intracellular Ca2+, which is dependent on the cell surface expression of the TCR/CD3 complex. No CD99 mAb-induced calcium mobilization was observed on TCR/CD3-modulated or TCR/CD3-negative T cells. To examine the impact of CD99 stimulation on subsequent cytokine production by T cells, we cross-linked CD99 molecules in the presence of a suboptimal TCR/CD3 trigger followed by determination of intracellular cytokine levels. Significantly, T cell lines as well as Th1 and Th0 clones synthesized TNF-alpha and IFN-gamma after this treatment. In contrast, Th2 clones were unable to produce IL-4 or IFN-gamma when stimulated in a similar fashion. We conclude that CD99 is a receptor that mediates TCR/CD3-dependent activation of resting PB T cells and specifically induces Th1-type cytokine production in polyclonally activated T cell lines, Th1 and Th0 clones.

Identification of CD68+lin- peripheral blood cells with dendritic precursor characteristics.

Expression of CD68 (macrosialin) in the absence of surface and lysosomal lineage marker molecules is a characteristic feature of T zone-associated plasmacytoid monocytes, which were recently shown to represent precursors of dendritic cells (DC). We demonstrate here a minor population of strongly CD68-positive (CD68bright) blood cells that lack all analyzed myeloid surface (CD14-, CD33-, CD13-, CD11b-, CD11c-) and lysosomal (myeloperoxidase, MPO- and lysozyme, LZ-) marker molecules (0.4 +/- 2% of the total mononuclear cells). These CD68bright, lineage marker-negative (lin-) cells can be induced to proliferate in the presence of IL-3. They do not acquire myeloid features even upon stimulation with granulocyte-macrophage CSF plus IL-1, IL-3, and IL-6. Instead, these cells develop typical DC characteristics upon culture. Furthermore, these CD68brightlin- DC precursors acquire mature DC characteristics (CD86+, CD83+, CD54bright) upon stimulation with CD40 ligand plus IL-3. A second subset of DC precursor-like blood cells was found to weakly express CD68 (0.3 +/- 0.2% of the total mononuclear cells) and to coexpress several myeloid lineage associated molecules (LZ+, CD11c+, CD33+, CD13+). Cells of this second subset resemble both previously described myeloid-related peripheral blood DC and germinal center DC. Analysis of peripheral blood leukocytes for CD68 thus revealed the existence of two cell subsets that phenotypically resemble lymphoid tissue-associated DC. The unique phenotype CD68brightlin- is highly reminiscent of T zone-associated plasmacytoid monocytes. CD68brightlin- blood leukocytes also functionally resemble plasmacytoid monocytes. The lack of all analyzed myeloid features by CD68brightlin- blood leukocytes suggests that these cells arise from a novel nonmyeloid human DC differentiation pathway.

Neutrophil granulocyte-committed cells can be driven to acquire dendritic cell characteristics.

Polymorphonuclear granulocytes (PMNs) are thought to fulfill their role in host defense primarily via phagocytosis and release of cytotoxic compounds and to be inefficient in antigen presentation and stimulation of specific T cells. Dendritic cells (DCs), in contrast, are potent antigen-presenting cells with the unique capacity to initiate primary immune responses. We demonstrate here that highly purified lactoferrin-positive immediate precursors of end-stage neutrophilic PMN (PMNp) can be reverted in their functional maturation program and driven to acquire characteristic DC features. Upon culture with the cytokine combination granulocyte/macrophage colony-stimulating factor plus interleukin 4 plus tumor necrosis factor alpha, they develop DC morphology and acquire molecular features characteristic for DCs. These molecular changes include neo-expression of the DC-associated surface molecules cluster of differentiation (CD)1a, CD1b, CD1c, human leukocyte antigen (HLA)-DR, HLA-DQ, CD80, CD86, CD40, CD54, and CD5, and downregulation of CD15 and CD65s. Additional stimulation with CD40 ligand induces also expression of CD83 and upregulates CD80, CD86, and HLA-DR. The neutrophil-derived DCs are potent T cell stimulators in allogeneic, as well as autologous, mixed lymphocyte reactions (MLRs), whereas freshly isolated neutrophils are completely unable to do so. In addition, neutrophil-derived DCs are at least 10,000 times more efficient in presenting soluble antigen to autologous T cells when compared to freshly isolated monocytes. Also, in functional terms, these neutrophil-derived DCs thus closely resemble "classical" DC populations.

Efficient retrovirus-mediated gene transfer of dendritic cells generated from CD34+ cord blood cells under serum-free conditions.

A retroviral-vector encoding the low affinity nerve growth factor receptor (LNGFR) was used to transduce dendritic cells (DCs) generated from CD34+ cord blood (CB) progenitor cells under serum-free conditions. Transduction efficiency was monitored by flow cytometry (FACS) using a specific monoclonal antibody. Prior to retroviral infections, CD34+ CB cells were stimulated for 60 h in a serum-free medium containing a DC differentiation inducing cytokine cocktail: stem cell factor (SCF), granulocyte/macrophage-colony stimulating factor (GM-CSF), tumor necrosis factor alpha (TNFalpha), and transforming growth factor beta 1 (TGF-beta1). Addition of flt3-ligand (FL) to the aforementioned growth factors significantly enhanced cell expansion (41.7+/-11.5 fold vs. 22.5+/-4.7 fold without FL) and generation of CD1a+ DCs (mean 45.7+/-9.8% vs. 28+/-6.5% without FL, n = 4,p = 0.01). Furthermore, FL significantly increased the proportion of CD1a+LNGFR+ cells (mean 10%+/-4.4% vs. 6%+/-2.4 without FL n = 4, p = 0.03). When serum-free viral supernatants were used to infect DCs progenitors under entirely serum-free conditions and with the most potent cytokine combination, approximately one-third of the CD1a+ DCs generated co-expressed the LNGFR gene. Moreover, the transduced gene was also identified in more mature CD1a+CD80+ and CD1a+CD86+ DCs after 12-14 days of culture. In addition, transduced CD1a+ DCs maintained their functional properties, stimulating allogeneic T cells with similar efficiency as nontransduced CD1a+ DCs. Thus, the serum-free system described allows efficient generation and transduction of CD1a+ DCs derived from CD34+ progenitor cells and may be very useful for future therapeutic applications of DCs.