Blood dendritic cells generated with Flt3 ligand and CD40 ligand prime CD8+ T cells efficiently in cancer patients

Flt3 ligand mobilizes dendritic cells (DCs) into blood, allowing generation in vivo of large numbers of DCs for immunotherapy. These immature DCs can be rapidly activated by soluble CD40 ligand (CD40L). We developed a novel overnight method using these cytokines to produce DCs for cancer immunotherapy. Flt3 ligand-mobilized DCs (FLDCs) were isolated, activated with CD40L, loaded with antigenic peptides from influenza matrix protein, hepatitis B core antigen, NY-ESO-1, MAGE-A4, and MAGE-A10, and injected into patients with resected melanoma. Three injections were given at 4-week intervals. Study end points included antigen-specific immune responses (skin reactions to peptides alone or peptide-pulsed FLDCs; circulating T-cell responses), safety, and toxicity. No patient had a measurable tumor. Six patients were entered. FLDCs were obtained, enriched, and cultured under Good Manufacturing Practice grade conditions. Overnight culture with soluble CD40L caused marked up-regulation of activation markers (CD83 and HLA-DR). These FLDCs were functional and able to stimulate antigen-specific T cells in vitro. No significant adverse events were attributable to FLDCs. Peptide-pulsed FLDCs caused strong local skin reactions up to 60 mm diameter with intense perivascular infiltration of T cells, exceeding those seen in our previous peptide-based protocols. Antigen-specific blood T-cell responses were induced, including responses to an antigen for which the patients were naive (hepatitis B core antigen) and MAGE-A10. MAGE-A10-specific T cells with a skewed T-cell receptor repertoire were detected in 1 patient in blood ex vivo and from tumor biopsies. Vaccination with FLDCs pulsed with peptides is safe and primes immune responses to cancer antigens.     

The early progenitors of mouse dendritic cells and plasmacytoid predendritic cells are within the bone marrow hemopoietic precursors expressing Flt3

Flt3 ligand (Flt3L) is a growth factor for hemopoietic progenitors and can promote the expansion of both conventional dendritic cells (DCs) and plasmacytoid predendritic cells (p-preDCs). The cells responding to Flt3L treatment and the precursors for the DCs and p-preDCs had not been fully characterized. We examined different mouse bone marrow (BM) hemopoietic precursor populations for the surface expression of Flt3 and tested them for early DC and p-preDC precursor activity. Most DC precursor activity, other than that given by multipotent hemopoietic stem cells, was within the downstream precursors expressing Flt3. The majority of mouse BM common lymphoid precursors expressed high levels of Flt3 and these were the most efficient precursors of both DCs and p-preDCs. In contrast, only a small proportion of the common myeloid precursors (CMPs) expressed Flt3, but the precursor activity for both DCs and p-preDCs was within this minor Flt3+ CMP fraction. The granulocyte and macrophage precursors and pro-B cells did not express Flt3 and had no DC or p-preDC precursor activity. These findings demonstrate that the early precursors for all DC subtypes are within the BM Flt3+ precursor populations, regardless of their lymphoid or myeloid lineage orientation.     

Decreased numbers of peripheral blood dendritic cells in patients with coronary artery disease are associated with diminished plasma Flt3 ligand levels and impaired plasmacytoid dendritic cell function

We investigated whether activation of circulating DCs (dendritic cells) or levels of Flt3L (FMS-like tyrosine kinase 3 ligand) and GM-CSF (granulocyte/macrophage colony-stimulating factor), haematopoietic growth factors important for DC differentiation, could account for reduced blood DC numbers in CAD (coronary artery disease) patients. Concentrations of Flt3L and GM-CSF were measured in plasma from CAD patients (n = 15) and controls (n = 12). Frequency and phenotype of mDCs (myeloid dendritic cells) and pDCs (plasmacytoid dendritic cells) were analysed by multicolour flow cytometry in fresh blood, and after overnight incubation with TLR (Toll-like receptor)-4 or -7 ligands LPS (lipopolysaccharide) or IQ (imiquimod). DC function was measured by IL (interleukin)-12 and IFN (interferon)-α secretion. Circulating numbers of CD11c+ mDCs and CD123+ pDCs and frequencies of CD86+ and CCR-7+ (CC chemokine receptor type?7) mDCs, but not pDCs, were declined in CAD. In addition, plasma Flt3L, but not GM-CSF, was lower in patients and positively correlated with blood DC counts. In response to LPS, mDCs up-regulated CD83 and CD86, but CCR-7 expression and IL-12 secretion remained unchanged, similarly in patients and controls. Conversely, pDCs from patients had lower CD83 and CCR-7 expression after overnight incubation and had a weaker IQ-induced up-regulation of CD83 and IFN-α secretion. In conclusion, our results suggest that reduced blood DC counts in CAD are, at least partly, due to impaired DC differentiation from bone marrow progenitors. Decreased levels of mDCs are presumably also explained by activation and subsequent migration to atherosclerotic plaques or lymph nodes. Although mDCs are functioning normally, pDCs from patients appeared to be both numerically and functionally impaired.     

NK cells mediate Flt3 ligand-induced protection of dendritic cell precursors in vivo from the inhibition by prostate carcinoma in the murine bone marrow metastasis model

Multiple observations suggest that suppression of the dendritic cell (DC) system might be one of the mechanisms used by the tumors to escape immune response. However, no in vivo data are available to support these in vitro observations. Here we have shown that murine prostate cancer inhibits DC generation (dendropoiesis) from the bone marrow precursors in the in vivo model in mice injected intrafemorally with RM1 prostate adenocarcinoma cells. Phenotyping of DC, generated from in vivo RM1-treated bone marrow cells, revealed a significant inhibition of dendropoiesis assessed as a percentage of CD11c+MHCII+, CD11c+CD86+, and CD11c+CD80+ cells. The stimulatory capacity of these DCs to induce T cell proliferation was also markedly decreased. Notably, Flt3 ligand-based therapy reversed the inhibitory effects of prostate cancer on dendropoiesis in vivo in wild-type and C.B-17 SCID (T and B cell deficient) mice, but not in SCID beige (T, B, and NK cell deficient) animals, suggesting a key role of NK cells in Flt3 ligand-mediated protection of dendropoiesis from tumor-induced inhibition in vivo. Thus, these data demonstrate that prostate cancer inhibits DC hematopoietic precursors in vivo in the bone marrow and this effect could be abolished by a systemic administration of growth factor Flt3 ligand.     

Interaction of mature CD3+CD4+ T cells with dendritic cells triggers the development of tertiary lymphoid structures in the thyroid

Ectopic expression of CC chemokine ligand 21 (CCL21) in the thyroid leads to development of lymphoid structures that resemble those observed in Hashimoto thyroiditis. Deletion of the inhibitor of differentiation 2 (Id2) gene, essential for generation of CD3-CD4+ lymphoid tissue-inducer (LTi) cells and development of secondary lymphoid organs, did not affect formation of tertiary lymphoid structures. Rather, mature CD3+CD4+ T cells were critical for the development of tertiary lymphoid structures. The initial stages of this process involved interaction of CD3+CD4+ T cells with DCs, the appearance of peripheral-node addressin-positive (PNAd+) vessels, and production of chemokines that recruit lymphocytes and DCs. These findings indicate that the formation of tertiary lymphoid structures does not require Id2-dependent conventional LTis but depends on a program initiated by mature CD3+CD4+ T cells.     

Flt3配体胞外域的原核表达纯化及对脐血CD34+细胞的扩增作用

背景:Fms 样酪氨酸激酶3配体(Flt3配体)是一种重要的生长因子,通过激活特定的酪氨酸激酶受体,调控造血细胞的生长、生存和/或分化,具有促进造血干细胞体外扩增的应用潜力.目的:构建pET32a(+)-hFLext原核表达载体,表达、纯化hFLext蛋白,观察其对脐血CD34+细胞的扩增作用.方法:克隆hFLext,构建pET32a(+)-hFLext重组表达载体.转化大肠杆菌 BL21,IPTG诱导蛋白表达,镍珠亲合层析纯化蛋白.磁珠分选脐血CD34+细胞,单独加入hFLext或联合干细胞因子、血小板生成素孵育1周,观察体外扩增作用.结果与结论:成功克隆hFLext,并构建了pET32a(+)-hFLext重组表达载体.在大肠杆菌BL21成功表达Trx-hFLext融合蛋白,经8 mol/L尿素变性包涵体蛋白,逐步透析复性,镍珠亲合层析纯化蛋白,成功获得高纯度的Trx-hFLext融合蛋白.Trx-hFLext融合蛋白不仅具有维持及轻度刺激CD34+细胞体外扩增的作用,并且与干细胞因子及血小板生成素具有协同作用,为造血干/祖细胞体外扩增研究奠定了基础.     

Flt3配体对多器官功能障碍综合征小鼠脾脏树突状细胞及细胞免疫功能的修复作用

目的探讨Flt3配体（FL）对多器官功能障碍综合征（MODS）晚期免疫失衡的修复作用与意义。方法按随机数字表法将90只实验鼠分为正常对照组、MODS组和FL治疗组，每组30只。用流式细胞技术检测各组脾脏树突状细胞（DC）、外周血单个核细胞主要组织相容性复合物Ⅱ类分子（I—A^b）表达变化及T细胞亚群变化，光、电镜下观察脾脏组织结构和DC变化。结果MODS组脾脏中未成熟DC明显增加（P〈0．05）；外周血单个核细胞I—A^b表达及CD4／CD8比值明显下降（P〈0．01和P〈0．05）；脾脏白髓消散，脾小体明显减少，DC多呈凋亡与退变崩解改变，周围淋巴细胞大量凋亡；活杀前动物死亡率为18％。治疗组小鼠脾脏中成熟DC数量明显增加（P〈0．05）；外周血单个核细胞I—A^b表达接近正常水平，CD4／CD8比值较MODS组明显上调；脾脏组织形态与DC的病理改变较MODS组明显减轻；实验鼠死亡率（7％）也明显降低。结论FL可以通过促进DC增生和活化，有效改善MODS晚期细胞免疫功能，进而缓解MODS的进程。     

The CD8+ dendritic cell subset selectively endocytoses dying cells in culture and in vivo

Dendritic cells (DCs) are able in tissue culture to phagocytose and present antigens derived from infected, malignant, and allogeneic cells. Here we show directly that DCs in situ take up these types of cells after fluorescent labeling with carboxyfluorescein succinimidyl ester (CFSE) and injection into mice. The injected cells include syngeneic splenocytes and tumor cell lines, induced to undergo apoptosis ex vivo by exposure to osmotic shock, and allogeneic B cells killed by NK cells in situ. The CFSE-labeled cells in each case are actively endocytosed by DCs in vivo, but only the CD8+ subset. After uptake, all of the phagocytic CD8+ DCs can form major histocompatibility complex class II-peptide complexes, as detected with a monoclonal antibody specific for these complexes. The CD8+ DCs also selectively present cell-associated antigens to both CD4+ and CD8+ T cells. Similar events take place with cultured DCs; CD8+ DCs again selectively take up and present dying cells. In contrast, both CD8+ and CD8- DCs phagocytose latex particles in culture, and both DC subsets present soluble ovalbumin captured in vivo. Therefore CD8+ DCs are specialized to capture dying cells, and this helps to explain their selective ability to cross present cellular antigens to both CD4+ and CD8+ T cells.     

Clinical applications of ex vivo cultured CD34+ cells and myeloid progenitors

After extensive preclinical work, hematopoietic cellular therapy has recently entered a new era of clinical trials involving ex vivo cultured cells. The evolution of hematopoietic cell culture from clonogenic assays to large-scale static culture systems and bioreactors, and the identification and production of hematopoietic growth factors, have in part made this possible. In addition, murine models have demonstrated encouraging results with regard to the feasibility of infusing cultured cells, as well as to the potential efficacy. Several trials have recently been published utilizing ex vivo generated hematopoietic progenitors and myeloid progenitors, and are reviewed here. The field of clinical hematopoietic cellular therapy, while still in its infancy, is progressing rapidly, and promises to offer improved therapeutic options.     

重组人Flt3配体在毕氏酵母中的表达及其对恶性造血细胞的体外作用

目的 用毕氏酵母（Ｐｉｃｈｉａ ｐａｓｔｏｒｉｓ）表达人可溶性Ｆｌｔ３配体（ｒｈＦＬ）,并观察ｒｈＦＬ对恶性造血细胞增殖的作用;探讨地塞米松（ＤＸＭ）对Ｆｌｔ３受体（Ｆｌｔ３Ｒ）表达及ｒｈＦＬ介导的恶性造血细胞增殖的影响。方法 人工合成ＦＬ基因片段,经基因重组技术获得重组质粒ｐＰＩＣＺα－ＦＬ,电转化毕氏酵母,筛选分泌ｒｈＦＬ的基因工程菌株,用流式细胞仪测定恶性造血细胞表面Ｆｌｔ３Ｒ的表达,用ＭＴ     

CD4+ CD25+ regulatory T cells control T helper cell type 1 responses to foreign antigens induced by mature dendritic cells in vivo

Recent evidence suggests that in addition to their well known stimulatory properties, dendritic cells (DCs) may play a major role in peripheral tolerance. It is still unclear whether a distinct subtype or activation status of DC exists that promotes the differentiation of suppressor rather than effector T cells from naive precursors. In this work, we tested whether the naturally occurring CD4+ CD25+ regulatory T cells (Treg) may control immune responses induced by DCs in vivo. We characterized the immune response induced by adoptive transfer of antigen-pulsed mature DCs into mice depleted or not of CD25+ cells. We found that the development of major histocompatibility complex class I and II-restricted interferon gamma-producing cells was consistently enhanced in the absence of Treg. By contrast, T helper cell (Th)2 priming was down-regulated in the same conditions. This regulation was independent of interleukin 10 production by DCs. Of note, splenic DCs incubated in vitro with Toll-like receptor ligands (lipopolysaccharide or CpG) activated immune responses that remained sensitive to Treg function. Our data further show that mature DCs induced higher cytotoxic activity in CD25-depleted recipients as compared with untreated hosts. We conclude that Treg naturally exert a negative feedback mechanism on Th1-type responses induced by mature DCs in vivo.     

骨髓基质细胞表面CD40分子配基化促进IL-6和Flt3配体的释放及其作用

目的：分析人骨髓基质细胞（BMSC）CD40分子及其配体（CD40L）的表达，观察BMSC经CD40激发型单抗（5C11）激发后，其培养上清中IL－3、IL－6、Flt3配体（FL）和干细胞因子（SCF）含量变化及对纯化脐血CD34^ 细胞的作用。方法：新鲜分离人骨髓单个核细胞，经体外培养获得BMSC。间接免疫荧光标记，流式细胞仪分析细胞表面CD40和CD40L的表达，并与5C11（20μg/ml）共同孵育，分别于24，48和72h取上清液，ELISA法测定IL－3、IL－6、FL和SCF含量；在与5C11共同培养24h后，收取培养上清，与纯化的脐血CD34^ 细胞共同孵育，1周后进行细胞计数、细胞集落培养，并用钙磷脂结合蛋白（Annexin V)标记，流式细胞仪分析细胞凋亡。结果：发现BMSC表达CD40分子，经5C11激发后，BMSC IL－6和FL分泌增加，而对IL－3及SCF含量无影响。BMSC经5C11激发培养后支持脐血CD34^ 细胞的增殖，培养7d后其细胞数和集落数显著多于对照组，且细胞凋亡率低，二者差异有显著性（P＜0．01）。结论：BMSC CD40分子配基化可促进IL－6和FL的分泌，并支持CD34^ 细胞的增殖，CD40／CD40L可能通过调节细胞因子的释放参与造血调控。     

4-1BB ligand stimulation enhances myeloid dendritic cell maturation from human umbilical cord blood CD34+ progenitor cells

In humans, at least two subsets of dendritic cells (DCs) are identified on the basis of differential surface expression of CD11c antigens. CD11c(+) and CD11c(-) cells are respectively of myeloid and lympholoid origin and functionally distinct, eliciting inflammatory and tolerant T cell responses. We investigated whether 4-1BB ligand (4-1BBL), a member of the tumor necrosis factor (TNF) family, is involved in the maturation process to mature myeloid DCs during in vitro DC differentiation from immature DCs derived from human umbilical cord blood (CB) CD34(+) progenitor cells. Enhanced levels of CD11c as well as immunostimulatory molecules such as CD86, MHC class II, and 4-1BBL were induced in response to 4-1BBL stimulation. These changes were accompanied by noticeable morphological transition from nonadherent to adherent myeloid-like DCs. Stimulation of 4-1BBL on DCs with 4-1BB-Fc or with 4-1BB-transfected Jurkat cells resulted in acquisition of capacity for the immature DCs to produce interleukin-12 (IL-12). This suggests that 4-1BBL may be an important mediator for maturation of CD11c(+) myeloid DCs, information of possible relevance for the design of DC-based vaccines with enhanced activity.     

Dendritic cells generated from CD34+ progenitor cells with flt3 ligand, c-kit ligand, GM-CSF, IL-4, and TNF-alpha are functional antigen-presenting cells resembling mature monocyte-derived dendritic cells

Dendritic cells (DCs) are powerful antigen-presenting cells. Because DCs are rare cells, methods to produce them in vitro are valuable ways to study their biologic properties and to generate cells for immunotherapy. This study defines the antigen-presenting properties of DCs generated in vitro from CD34+ cells of patients with breast cancer. The combination of cytokines flt3 ligand + c-kit ligand + granulocyte-macrophage colony-stimulating factor (GM-CSF) + interleukin-4 (IL-4) + tumor necrosis factor-alpha (TNF-alpha) was used to maximize the output of mature DCs in the culture of CD34+ cells while minimizing the production of monocytes. Cells grew and differentiated into DCs as measured by a time-dependent upregulation of cell surface antigens major histocompatibility complex class II, CD1a, CD80, CD86, CD40, and CD4, so that 40% +/- 9% (n = 6) of cells in culture at day 15 were CD1a+CD14-. Markers were acquired in the same sequence as on monocytes induced to differentiate with GM-CSF + IL-4. Differentiation was marked by a time-dependent increase in allostimulatory function, which, at its peak, was more potent than in cultures of DCs generated from monocytes with GM-CSF + IL-4, but was comparable on a cell-to-cell basis to that of mature monocytes cultured in flt3-ligand + c-kit-ligand + GM-CSF + IL-4 + TNF-alpha. Both CD34+ cell-derived and monocyte-derived DCs were able to process and to present tetanus toxoid and keyhole limpet hemocyanin to autologous T cells and to present major histocompatibility class I-binding peptides to CD8+ cytotoxic T lymphocytes inducing interferon-gamma production. Altogether, these results suggest that DCs generated from CD34+ cells of patients with breast cancer with flt3 ligand, c-kit ligand, GM-CSF, IL-4, and TNF-alpha are competent antigen-presenting cells, particularly for CD8+ cytotoxic T lymphocytes, and resemble mature monocyte-derived DCs in the assays described here.