小鼠骨髓源性树突状细胞体外诱导培养方法的比较研究

目的探讨最佳体外诱导培养小鼠成熟树突状细胞（dendritic cells,DC）的方法。方法分离、纯化6周龄C57BL／6小鼠骨髓单核细胞,以含10％胎牛血清、20ng／ml重组小鼠粒细胞-巨噬细胞集落刺激因子（GM—CSF）和10ng／ml重组小鼠白细胞介素-4（IL-4）的RPMI-1640培养基培养7d,然后将细胞分成对照未刺激组、肿瘤坏死因子-α（TNF-α）刺激组和TNF-α＋脂多糖（lipopolysaccharides,LPS）刺激组。继续培养48h后,观察各组细胞形态,检测IL-12、IL-6浓度及细胞表面标志CD11c、CD80、CD86和MHC II。结果培养9d后,两刺激组培养的细胞经相差显微镜观察有DC生长。TNF—α刺激组细胞培养上清液中IL-6、IL-12含量显著高于对照组（P〈0．01）,但显著低于TNF—α＋LPS刺激组（P〈0．05）。3组均高表达CD11c,各组间无显著差异;而CD80、CD86和MHC II表达阳性率TNF-α刺激组显著高于对照组（P〈0．01）,TNF-α＋LPS刺激组显著高于单纯TNF—α刺激组（P〈0．05）。结论联合使用TNF-α与LPS刺激可使DC成熟度提高,分泌IL-6、IL-12增加。     

Isolation of Mouse Lung Dendritic Cells

Lung dendritic cells (DC) play a fundamental role in sensing invading pathogens ^1,2 as well as in the control of tolerogenic responses ³ in the respiratory tract. At least three main subsets of lung dendritic cells have been described in mice: conventional DC (cDC) ⁴, plasmacytoid DC (pDC) ⁵ and the IFN-producing killer DC (IKDC) ^6,7. The cDC subset is the most prominent DC subset in the lung ⁸. The common marker known to identify DC subsets is CD11c, a type I transmembrane integrin (β2) that is also expressed on monocytes, macrophages, neutrophils and some B cells ⁹. In some tissues, using CD11c as a marker to identify mouse DC is valid, as in spleen, where most CD11c⁺ cells represent the cDC subset which expresses high levels of the major histocompatibility complex class II (MHC-II). However, the lung is a more heterogeneous tissue where beside DC subsets, there is a high percentage of a distinct cell population that expresses high levels of CD11c bout low levels of MHC-II. Based on its characterization and mostly on its expression of F4/80, an splenic macrophage marker, the CD11c^hiMHC-II^lo lung cell population has been identified as pulmonary macrophages 10 and more recently, as a potential DC precursor ¹¹. In contrast to mouse pDC, the study of the specific role of cDC in the pulmonary immune response has been limited due to the lack of a specific marker that could help in the isolation of these cells. Therefore, in this work, we describe a procedure to isolate highly purified mouse lung cDC. The isolation of pulmonary DC subsets represents a very useful tool to gain insights into the function of these cells in response to respiratory pathogens as well as environmental factors that can trigger the host immune response in the lung. Download video file.^{(55M, mov)}     

大鼠骨髓来源未成熟与成熟树突状细胞的对比研究

目的:对比培养大鼠骨髓来源的未成熟树突状细胞与成熟树突状细胞,并从形态学、表型及功能检测等多方面进行对比研究,为后续的实验做出基础研究。方法:大鼠脱臼法处死后取两侧胫骨、股骨,PBS冲洗骨髓腔收集骨髓细胞,经GM-CSF和IL-4刺激培养六天后,对比研究经LPS刺激组与未经LPS刺激培养组细胞状况。结果:①成熟树突状细胞悬浮生长,集落分散,扫描电镜下见其突起数目明显多于未成熟树突状细胞。②成熟树突状细胞高表达表面标记分子CD80、CD86、MHCⅡ,而未成熟树突状细胞均低表达。③成熟树突状细胞培养基上清中IL-12水平高,而未成熟树突状细胞培养基上清中IL-12水平低。④成熟树突状细胞具有强的刺激T细胞增殖能力,而未成熟树突状细胞基本不具有诱导T细胞增殖能力。结论:未成熟状态的树突状细胞具备致耐受原性,可抑制T细胞的应答,而成熟状态的树突状细胞由于获得了免疫刺激潜能从而会对炎性刺激做出反应。     

Myogenic Reprogramming of Bone Marrow Derived Cells in a W41Dmdmdx Deficient Mouse Model

Lack of expression of dystrophin leads to degeneration of muscle fibers and infiltration of connective and adipose tissue. Cell transplantation therapy has been proposed as a treatment for intractable muscle degenerative disorders. Several reports have demonstrated the ability of bone-marrow derived cells (BMDC) to contribute to non-haematopoietic tissues including epithelium, heart, liver, skeletal muscle and brain following transplantation by means of fusion and reprogramming. A key issue is the extent to which fusion and reprogramming can occur in vivo, particularly under conditions of myogenic deterioration.To investigate the therapeutic potential of bone marrow transplantation in monogenetic myopathy, green fluorescent protein-positive (GFP⁺) bone marrow cells were transplanted into non-irradiated c-kit receptor – deficient (W⁴¹) mdx mice. This model allows BMDC reconstitution in the absence of irradiation induced myeloablation. We provide the first report of BMDC fusion in a W⁴¹/Dmd^mdx deficient mouse model.In the absence of irradiation induced injury, few GFP⁺ cardiomyocytes and muscle fibres were detected 24 weeks post BMT. It was expected that the frequency of fusion in the hearts of W⁴¹Dmd^mdx mice would be similar to frequencies observed in infarcted mice [1].Although, it is clear from this study that individual cardiomyocytes with monogenetic deficiencies can be rescued by fusion, it is as clear that in the absence of irradiation, the formation of stable and reprogrammed fusion hybrids occurs, with the current techniques, at very low levels in non-irradiated recipients.     

A Mouse Model of Adoptive Immunotherapeutic Targeting of Autoimmune Arthritis Using Allo-Tolerogenic Dendritic Cells

Objective

Tolerogenic dendritic cells (tDCs) are immunosuppressive cells with potent tolerogenic ability and are promising immunotherapeutic tools for treating rheumatoid arthritis (RA). However, it is currently unknown whether allogeneic tDCs (allo-tDCs) induce tolerance in RA, and whether the numbers of adoptively transferred allo-tDCs, or the requirement for pulsing with relevant auto-antigens are important.

Methods

tDCs were derived from bone marrow precursors of C57BL/B6 mice, which were induced in vitro by GM-CSF, IL-10 and TGF-β1. Collagen-induced arthritis (CIA) was modeled in D1 mice by immunization with type II collagen (CII) to test the therapeutic ability of allo-tDCs against CIA. Clinical and histopathologic scores, arthritic incidence, cytokine and anti-CII antibody secretion, and CD4⁺Th subsets were analyzed.

Results

tDCs were characterized in vitro by a stable immature phonotype and a potent immunosuppressive ability. Following adoptive transfer of low doses (5×10⁵) of CII-loaded allo-tDCs, a remarkable anti-arthritic activity, improved clinical scores and histological end-points were found. Serological levels of inflammatory cytokines and anti-CII antibodies were also significantly lower in CIA mice treated with CII-pulsed allo-tDCs as compared with allo-tDCs. Moreover, treatment with allo-tDCs altered the proportion of Treg/Th17 cells.

Conclusion

These findings suggested that allo-tDCs, especially following antigen loading, reduced the severity of CIA in a dose-dependent manner. The dampening of CIA was associated with modulated cytokine secretion, Treg/Th17 polarization and inhibition of anti-CII secretion. This study highlights the potential therapeutic utility of allo-tDCs in autoimmune arthritis and should facilitate the future design of allo-tDC immunotherapeutic strategies against RA.     

丹参酸甲对小鼠骨髓来源树突状细胞表型及其部分功能的影响

探讨丹参酸甲对小鼠骨髓来源树突状细胞(dendritic cells,DCs)表型及其部分免疫功能的影响,可为丹参酸甲的临床应用提供理论和实验依据。首先,分离培养小鼠骨髓细胞,并利用IL-4和GM-CSF诱生树突状细胞。随后,进行丹参酸甲体外处理,采用流式细胞术检测丹参酸甲对树突状细胞百分率、细胞表面分子(MHC-Ⅱ、CD80、CD86)表达水平及摄取能力的影响;采用ELISA检测各组DC与T细胞共培养后上清液中细胞因子的含量。结果显示:经10μg/mL丹参酸甲处理后,树突状细胞的百分率、FITC-Dextran阳性细胞的数量明显增加,而其表面分子MHC-Ⅱ~(high)/MHC-Ⅱ~(low)比例、MHC-Ⅱ~(high)和MHC-Ⅱ~(low)平均荧光强度、CD80和CD86的表达水平均显著降低。此外,丹参酸甲可增强DC诱导的T细胞分泌IL-10的能力,同时抑制T细胞分泌INF-γ的能力。以上结果说明,丹参酸甲可诱导骨髓细胞向DC分化;并可通过增强DC对抗原的摄取吞噬能力,下调成熟DC的表面标志物表达水平,抑制树突状细胞的成熟,减轻DC与T细胞相互作用介导的炎症反应。这为丹参酸甲在临床用于T细胞过度活化引发的免疫性疾病提供了依据。     

Ginseng Berry Extract Promotes Maturation of Mouse Dendritic Cells

Ginseng extract has been shown to possess certain anti-virus, anti-tumor and immune-activating effects. However, the immunostimulatory effect of ginseng berry extract (GB) has been less well characterized. In this study, we investigated the effect of GB on the activation of mouse dendritic cells (DCs) in vitro and in vivo. GB treatment induced up-regulation of co-stimulatory molecules in bone marrow-derived DCs (BMDCs). Interestingly, GB induced a higher degree of co-stimulatory molecule up-regulation than ginseng root extract (GR) at the same concentrations. Moreover, in vivo administration of GB promoted up-regulation of CD86, MHC class I and MHC class II and production of IL-6, IL-12 and TNF-α in spleen DCs. GB also promoted the generation of Th1 and Tc1 cells. Furthermore, Toll like receptor 4 (TLR4) and myeloid differentiation primary response 88 (MyD88) signaling pathway were essential for DC activation induced by GB. In addition, GB strongly prompted the proliferation of ovalbumin (OVA)-specific CD4 and CD8 T cells. Finally, GB induced DC activation in tumor-bearing mice and the combination of OVA and GB treatment inhibited B16-OVA tumor cell growth in C57BL/6 mice. These results demonstrate that GB is a novel tumor therapeutic vaccine adjuvant by promoting DC and T cell activation.     

CD8+ T Cells Cause Disability and Axon Loss in a Mouse Model of Multiple Sclerosis

Background

The objective of this study was to test the hypothesis that CD8⁺ T cells directly mediate motor disability and axon injury in the demyelinated central nervous system. We have previously observed that genetic deletion of the CD8⁺ T cell effector molecule perforin leads to preservation of motor function and preservation of spinal axons in chronically demyelinated mice.

Methodology/Principal Findings

To determine if CD8⁺ T cells are necessary and sufficient to directly injure demyelinated axons, we adoptively transferred purified perforin-competent CD8⁺ spinal cord-infiltrating T cells into profoundly demyelinated but functionally preserved perforin-deficient host mice. Transfer of CD8⁺ spinal cord-infiltrating T cells rapidly and irreversibly impaired motor function, disrupted spinal cord motor conduction, and reduced the number of medium- and large-caliber spinal axons. Likewise, immunodepletion of CD8⁺ T cells from chronically demyelinated wildtype mice preserved motor function and limited axon loss without altering other disease parameters.

Conclusions/Significance

In multiple sclerosis patients, CD8⁺ T cells outnumber CD4⁺ T cells in active lesions and the number of CD8⁺ T cells correlates with the extent of ongoing axon injury and functional disability. Our findings suggest that CD8⁺ T cells may directly injure demyelinated axons and are therefore a viable therapeutic target to protect axons and motor function in patients with multiple sclerosis.     

Acetyl-L-Carnitine Improves Behavior and Dendritic Morphology in a Mouse Model of Rett Syndrome

Rett syndrome (RTT) is a devastating neurodevelopmental disorder affecting 1 in 10,000 girls. Approximately 90% of cases are caused by spontaneous mutations in the X-linked gene encoding methyl-CpG-binding protein 2 (MeCP2). Girls with RTT suffer from severe motor, respiratory, cognitive and social abnomalities attributed to early deficits in synaptic connectivity which manifest in the adult as a myriad of physiological and anatomical abnormalities including, but not limited to, dimished dendritic complexity. Supplementation with acetyl-L-carnitine (ALC), an acetyl group donor, ameliorates motor and cognitive deficits in other disease models through a variety of mechanisms including altering patterns of histone acetylation resulting in changes in gene expression, and stimulating biosynthetic pathways such as acetylcholine. We hypothesized ALC treatment during critical periods in cortical development would promote normal synaptic maturation, and continuing treatment would improve behavioral deficits in the Mecp2^1lox mouse model of RTT. In this study, wildtype and Mecp2^1lox mutant mice received daily injections of ALC from birth until death (postnatal day 47). General health, motor, respiratory, and cognitive functions were assessed at several time points during symptom progression. ALC improved weight gain, grip strength, activity levels, prevented metabolic abnormalities and modestly improved cognitive function in Mecp2 null mice early in the course of treatment, but did not significantly improve motor or cognitive functions assessed later in life. ALC treatment from birth was associated with an almost complete rescue of hippocampal dendritic morphology abnormalities with no discernable side effects in the mutant mice. Therefore, ALC appears to be a promising therapeutic approach to treating early RTT symptoms and may be useful in combination with other therapies.     

Dysregulated Cytokine Production by Dendritic Cells Modulates B Cell Responses in the NZM2410 Mouse Model of Lupus

The breakdown in tolerance of autoreactive B cells in the lupus-prone NZM2410-derived B6.Sle1.Sle2.Sle3 (TC) mice results in the secretion of autoantibodies. TC dendritic cells (DCs) enhance B cell proliferation and antibody secretion in a cytokine-dependent manner. However, the specific cytokine milieu by which TC DCs activate B cells was not known. In this study, we compared TC and C57BL/6 (B6) control for the distribution of DC subsets and for their production of cytokines affecting B cell responses. We show that TC DCs enhanced B cell proliferation through the production of IL-6 and IFN-γ, while antibody secretion was only dependent on IL-6. Pre-disease TC mice showed an expanded PDCA1⁺ cells prior to disease onset that was localized to the marginal zone and further expanded with age. The presence of PDCA1⁺ cells in the marginal zone correlated with a Type I Interferon (IFN) signature in marginal zone B cells, and this response was higher in TC than B6 mice. In vivo administration of anti-chromatin immune complexes upregulated IL-6 and IFN-γ production by splenic DCs from TC but not B6 mice. The production of BAFF and APRIL was decreased upon TC DC stimulation both in vitro and in vivo, indicating that these B cell survival factors do not play a role in B cell modulation by TC DCs. Finally, TC B cells were defective at downregulating IL-6 expression in response to anti-inflammatory apoptotic cell exposure. Overall, these results show that the TC autoimmune genetic background induces the production of B cell-modulating inflammatory cytokines by DCs, which are regulated by the microenvironment as well as the interplay between DC.     

树突状细胞对胃癌前病变的免疫保护分析

摘要 目的：探究树突状细胞(Dendritic cells,DC)对胃癌的免疫保护作用。方法：选择2016年1月至2018年1月于我院接受治疗的145例胃癌、39例慢性萎缩性胃炎、21例不典型增生、27例肠上皮化生以及20例正常对照组患者为研究对象,分别采集其胃粘膜标本进行染色,记录和比较其胃粘膜中S100⁺、CD4⁺和CD8⁺细胞的数量、平均面积以及平均吸光度,并将胃癌患者分为中分化腺癌(49例)、低分化腺癌(53例)和未分化癌(43例)进行对比。结果：(1)胃癌组、慢性萎缩性胃炎组、不典型增生、肠上皮化生组的胃粘膜S100⁺阳性细胞计数明显高于正常对照组（P<0.05）,胃癌组平均吸光度低于对照组,其他3组平均吸光度显著高于对照组,(P<0.05);胃癌组平均面积与正常对照组相比无差异(P>0.05),其他三组平均面积显著高于对照组（P<0.05）;(2)慢性萎缩性胃炎组、肠上皮化生组、不典型增生组患者CD4⁺细胞数均低于对照组(P<0.05);胃癌组、慢性萎缩性胃炎组、肠上皮化生组患者平均面积均低于对照组(P<0.05);胃癌组、慢性萎缩性胃炎组、不典型增生、肠上皮化生组平均吸光度均低于对照组(P<0.05);(3)慢性萎缩性胃炎组、肠上皮化生组、不典型增生组患者CD8⁺细胞数明显高于对照组(P<0.05),胃癌组稍低于对照组(P>0.05);胃癌组患者平均面积低于对照组(P<0.05);胃癌组患者平均吸光值低于对照组,慢性萎缩性胃炎组、肠上皮化生组患者高于对照组(P均<0.05);(4)随着胃癌分化程度的降低,胃癌患者DC细胞数有降低趋势。结论：胃癌前病变患者胃粘膜中DC数量会显著增多,免疫功能加强,DC细胞数量会随胃癌分化程度的降低而减少,分析其原因与DC细胞能够抑制癌前病变有关。     

Developmental Regulation by Cytokines of Bone Marrow-Derived Dendritic Cells and Epidermal Langerhans Cells

Dendritic cells (DC) are specialized antigen-presenting cells involved in T cell-mediated immune responses. Differentiation and functional maturation of the DC are now known to be regulated by various cytokines, including TGF-β1. The experiments of this study examined the effect of other cytokines, such as IL-4, IL-10 and IL-6, on the differentiation and maturation of bone marrow (BM)-derived DC (BM-DC) and epidermal Langerhans cells (LC). When IL-6 or IL-10 was added to cultures of BM cells in the presence of GM-CSF, both cytokines, as in the case of TGF-β1, suppressed the maturation of DC in terms of the expression of adhesion and costimulatory molecules and T cell-stimulating activity. In contrast, IL-4 was not suppressive but rather supportive for the differentiation of DC. However, these suppressive cytokines hardly counteracted the maturation-inducing activity of TNF-α when added to cultures of immature DC. In addition, they appeared to block the overmaturation of DC, which is characterized by a loss of MHC class II molecules. Regarding LC maturation in epidermal cell cultures, IL-6 and IL-10 were inhibitory for the expression of CD86 and CD80 in a dose-dependent fashion. Unlike BM-DC, LC maturation was slightly enhanced by TGF-β1. The protein antigen-presentation by LC to Th1 clone was not affected by IL-6, but slightly reduced by IL-10. These results suggest that each cytokine contributes to regulate the differentiation and maturation of DC at a different developmental stage.     

Decreased Bone Formation Explains Osteoporosis in a Genetic Mouse Model of Hemochromatosiss

Osteoporosis may complicate iron overload diseases such as genetic hemochromatosis. However, molecular mechanisms involved in the iron-related osteoporosis remains poorly understood. Recent in vitro studies support a role of osteoblast impairment in iron-related osteoporosis. Our aim was to analyse the impact of excess iron in Hfe^-/- mice on osteoblast activity and on bone microarchitecture. We studied the bone formation rate, a dynamic parameter reflecting osteoblast activity, and the bone phenotype of Hfe^−/− male mice, a mouse model of human hemochromatosis, by using histomorphometry. Hfe^−/− animals were sacrificed at 6 months and compared to controls. We found that bone contains excess iron associated with increased hepatic iron concentration in Hfe^−/− mice. We have shown that animals with iron overload have decreased bone formation rate, suggesting a direct impact of iron excess on active osteoblasts number. For bone mass parameters, we showed that iron deposition was associated with bone loss by producing microarchitectural impairment with a decreased tendency in bone trabecular volume and trabecular number. A disorganization of trabecular network was found with marrow spaces increased, which was confirmed by enhanced trabecular separation and star volume of marrow spaces. These microarchitectural changes led to a loss of connectivity and complexity in the trabecular network, which was confirmed by decreased interconnectivity index and increased Minkowski’s fractal dimension. Our results suggest for the first time in a genetic hemochromatosis mouse model, that iron overload decreases bone formation and leads to alterations in bone mass and microarchitecture. These observations support a negative effect of iron on osteoblast recruitment and/or function, which may contribute to iron-related osteoporosis.     

香菇多糖对小鼠骨髓树突状细胞表型和功能的影响

通过研究香菇多糖(Lentinan,LNT)对小鼠骨髓源树突状细胞(bone marrow dendritic cells,BMDCs)功能调节的机制,进一步阐明香菇多糖的免疫活性。本实验将BMDCs分成脂多糖(LPS)阳性对照组、LNT处理组和RPMI1640空白对照组,应用酸性磷酸酶活性检测、流式细胞仪检测技术、吞噬实验、酶联免疫吸附试验检测各组BMDCs表型和功能的各种指标。结果显示,LNT(50μg/mL)处理组BMDCs酸性磷酸酶活性降低;BMDCs吞噬能力比RPMI1640空白对照组明显下降;BMDCs表面MHCⅡ、CD40、CD83、CD80、CD86和DEC205的表达增加;BMDCs白细胞介素12(IL-12)、白细胞介素10(IL-10)和肿瘤坏死因子-α(TNF-α)的表达增加。证明了适宜浓度的LNT可以促进BMDCs表型及功能的成熟。     

Dendritic Signals Command Firing Dynamics in a Mathematical Model of Cerebellar Purkinje Cells

Dendrites of cerebellar Purkinje cells (PCs) respond to brief excitations from parallel fibers with lasting plateau depolarizations. It is unknown whether these plateaus are local events that boost the synaptic signals or they propagate to the soma and directly take part in setting the cell firing dynamics. To address this issue, we analyzed a likely mechanism underlying plateaus in three representations of a reconstructed PC with increasing complexity. Analysis in an infinite cable suggests that Ca plateaus triggered by direct excitatory inputs from parallel fibers and their mirror signals, valleys (putatively triggered by the local feed forward inhibitory network), cannot propagate. However, simulations of the model in electrotonic equivalent cables prove that Ca plateaus (resp. valleys) are conducted over the entire cell with velocities typical of passive events once they are triggered by threshold synaptic inputs that turn the membrane current inward (resp. outward) over the whole cell surface. Bifurcation analysis of the model in equivalent cables, and simulations in a fully reconstructed PC both indicate that dendritic Ca plateaus and valleys, respectively, command epochs of firing and silencing of PCs.     

25(OH)D3 Affects the Maturation and Function of Mouse Bone Marrow-Derived Dendritic Cells Stimulated by Mycobacterium Bovis BCG

It has been shown that vitamin D deficiency increases an individual’s susceptibility to tuberculosis (TB). However, very little is known about the effect of vitamin D on the immune response to Mycobacterium tuberculosis (M. tb) in dendritic cells (DCs). Because DCs play an important role in TB infection, we investigated the phenotypic characteristics and functional capabilities of mouse bone marrow-derived dendritic cells (BMDCs) after stimulation with Bacillus Calmette-Guérin (BCG) in the presence or absence of 25(OH)D₃(100 nM). Bone marrow cells from mice were cultured with GM-CSF (20 ng/ml) and were then treated with 25(OH)D₃ for 7 days. On day 6, 5 µg/ml of BCG (≥1.0×10⁶ CFU/mg) was added to the cells for 24 hours, and on day 7, the non-adherent cells were harvested for phenotypic and functional analyses. After incubation with 25(OH)D₃, the expression levels of MHC-II and CD86 on the surface of the dendritic cells (DCs) and the ability of the DCs to stimulate proliferation of allogeneic mixed lymphocytes were lower than control cells (p<0.05). Furthermore, the level of Interleukin (IL) -4 secreted by the BMDCs in the 25(OH)D₃ culture was lower than that in the control culture (p<0.01). However, the BMDCs cultured with 25(OH)D₃ produced significantly higher levels of IL-2, IL-6, IL-10 and interferon gamma(IFN-γ) than those in the control culture (p<0.05). These findings suggest that 25(OH)D₃ modulates the immune response during mycobacterial infection by affecting the maturation and function of DCs.     

Mouse Bone Marrow-Derived Mesenchymal Stromal Cells Turn Activated Macrophages into a Regulatory-Like Profile

In recent years it has become clear that the therapeutic properties of bone marrow-derived mesenchymal stromal cells (MSC) are related not only to their ability to differentiate into different lineages but also to their capacity to suppress the immune response. We here studied the influence of MSC on macrophage function. Using mouse thioglycolate-elicited peritoneal macrophages (M) stimulated with LPS, we found that MSC markedly suppressed the production of the inflammatory cytokines TNF-α, IL-6, IL-12p70 and interferon-γ while increased the production of IL-10 and IL-12p40. Similar results were observed using supernatants from MSC suggesting that factor(s) constitutively released by MSC are involved. Supporting a role for PGE₂ we observed that acetylsalicylic acid impaired the ability of MSC to inhibit the production of inflammatory cytokines and to stimulate the production of IL-10 by LPS-stimulated M. Moreover, we found that MSC constitutively produce PGE2 at levels able to inhibit the production of TNF-α and IL-6 by activated M. MSC also inhibited the up-regulation of CD86 and MHC class II in LPS-stimulated M impairing their ability to activate antigen-specific T CD4+ cells. On the other hand, they stimulated the uptake of apoptotic thymocytes by M. Of note, MSC turned M into cells highly susceptible to infection with the parasite Trypanosoma cruzi increasing more than 5-fold the rate of M infection. Using a model of inflammation triggered by s.c. implantation of glass cylinders, we found that MSC stimulated the recruitment of macrophages which showed a low expression of CD86 and the MHC class II molecule Ia^b and a high ability to produce IL-10 and IL-12p40, but not IL-12 p70. In summary, our results suggest that MSC switch M into a regulatory profile characterized by a low ability to produce inflammatory cytokines, a high ability to phagocyte apoptotic cells, and a marked increase in their susceptibility to infection by intracellular pathogens.