[Interprofessional Care of Patients with Rheumatoid Arthritis from the Perspective of a General Practitioner Perspective: Results of a Cross-sectional Study]. / Interprofessionelle Versorgung von Patienten mit rheumatoider Arthritis aus hausärztlicher Sicht: Ergebnisse einer Querschnittserhebung.

BACKGROUND: General practitioners, specialists, occupational and physical therapists, nursing services and other professional groups are all involved in the treatment of patients with rheumatoid arthritis. This study aims to describe interprofessional cooperation in daily ambulatory care from the perspective of a general practitioner. METHODS: The cross-sectional study investigated cooperation between general practitioners (n=121 in 68 medical practices) and several other health care providers in Hesse and Rhineland Palatinate, Germany, from February to September 2017. It was part of the prospective cohort study PANORA (Prevalence of anti-cyclic citrullinated peptide (anti-CCP) positivity in patients with new onset of non-specific musculoskeletal symptoms). The questionnaire that was used contained closed-ended questions on socio-demographics and frequency of contact, and asked physicians to assess and weigh existing collaboration. Descriptive statistics were used for data analysis. RESULTS: When caring for patients with rheumatoid arthritis, 70%, of the physicians often took responsibility for synchronizing medications, and discussing diagnoses and test results. The most frequent cooperation was with rheumatologists and was considered as highly important but the least satisfactory. The second most frequent cooperation was with physical therapists and this was also rated as very important. Physicians had highest level of satisfaction with their collaboration with the nursing services. CONCLUSION: This study shows that general practitioners perform several medical tasks when treating patients with rheumatoid arthritis. During the process, they work together with several health care providers to various degrees. Cooperation with rheumatologists and physical therapists is particularly important to general practitioners; cooperation with rheumatologists is considered inadequate and in need of improvement.

High impact of COVID-19 in long-term care facilities, suggestion for monitoring in the EU/EEA, May 2020.

Residents in long-term care facilities (LTCF) are a vulnerable population group. Coronavirus disease (COVID-19)-related deaths in LTCF residents represent 30-60% of all COVID-19 deaths in many European countries. This situation demands that countries implement local and national testing, infection prevention and control, and monitoring programmes for COVID-19 in LTCF in order to identify clusters early, decrease the spread within and between facilities and reduce the size and severity of outbreaks.

Rapamycin combined with TGF-ß converts human invariant NKT cells into suppressive Foxp3+ regulatory cells.

Invariant NKT (iNKT) cells constitute a versatile T cell subset with important regulatory functions, which are thought to result essentially from their capacity to promptly produce cytokines that influence the Th1/Th2 balance. In this study, we report that these cells can also express Foxp3, an important transcriptional regulator associated with suppressive activity, once they have been exposed to TGF-ß. Foxp3 was expressed by iNKT cells from both peripheral and cord blood. CD4(+) iNKT cells acquired Foxp3 expression preferentially, although a lower proportion of their CD4(-) counterpart also became positive. All Foxp3(+) iNKT cells displayed CD25 but not necessarily CTLA4 or GITR, regardless of the upregulation of these markers in the presence of TGF-ß. Exposure to TGF-ß decreased IL-4 and IFN-γ production while increasing IL-10, independently from Foxp3 expression. IL-17 was not detected. TGF-ß induced high levels of Foxp3, but no suppressor activity, which emerged only in the presence of rapamycin. Peripheral and cord blood Foxp3(+) iNKT cells suppressed the proliferation of conventional autologous and heterologous CD4(+) T cells equally, in a cell contact-dependent and Ag-independent manner. Our findings demonstrate that human iNKT cells become suppressive in the presence of TGF-ß plus rapamycin, thus adding a new facet to their complex functional properties.

Ineffective erythropoiesis with reduced red blood cell survival in serotonin-deficient mice.

Serotonin (5-HT) has long been recognized as a neurotransmitter in the central nervous system, where it modulates a variety of behavioral functions. Availability of 5-HT depends on the expression of the enzyme tryptophan hydroxylase (TPH), and the recent discovery of a dual system for 5-HT synthesis in the brain (TPH2) and periphery (TPH1) has renewed interest in studying the potential functions played by 5-HT in nonnervous tissues. Moreover, characterization of the TPH1 knockout mouse model (TPH1(-/-)) led to the identification of unsuspected roles for peripheral 5-HT, revealing the importance of this monoamine in regulating key physiological functions outside the brain. Here, we present in vivo data showing that mice deficient in peripheral 5-HT display morphological and cellular features of ineffective erythropoiesis. The central event occurs in the bone marrow where the absence of 5-HT hampers progression of erythroid precursors expressing 5-HT(2A) and 5-HT(2B) receptors toward terminal differentiation. In addition, red blood cells from 5-HT-deficient mice are more sensitive to macrophage phagocytosis and have a shortened in vivo half-life. The combination of these two defects causes TPH1(-/-) animals to develop a phenotype of macrocytic anemia. Direct evidence for a 5-HT effect on erythroid precursors is provided by supplementation of the culture medium with 5-HT that increases the proliferative capacity of both 5-HT-deficient and normal cells. Our thorough analysis of TPH1(-/-) mice provides a unique model of morphological and functional aberrations of erythropoiesis and identifies 5-HT as a key factor for red blood cell production and survival.

Identification of an IL-17-producing NK1.1(neg) iNKT cell population involved in airway neutrophilia.

Invariant natural killer T (iNKT) cells are an important source of both T helper type 1 (Th1) and Th2 cytokines, through which they can exert beneficial, as well as deleterious, effects in a variety of inflammatory diseases. This functional heterogeneity raises the question of how far phenotypically distinct subpopulations are responsible for such contrasting activities. In this study, we identify a particular set of iNKT cells that lack the NK1.1 marker (NK1.1(neg)) and secrete high amounts of interleukin (IL)-17 and low levels of interferon (IFN)-gamma and IL-4. NK1.1(neg) iNKT cells produce IL-17 upon synthetic (alpha-galactosylceramide [alpha-GalCer] or PBS-57), as well as natural (lipopolysaccharides or glycolipids derived from Sphingomonas wittichii and Borrelia burgdorferi), ligand stimulation. NK1.1(neg) iNKT cells are more frequent in the lung, which is consistent with a role in the natural immunity to inhaled antigens. Indeed, airway neutrophilia induced by alpha-GalCer or lipopolysaccharide instillation was significantly reduced in iNKT-cell-deficient Jalpha18(-/-) mice, which produced significantly less IL-17 in their bronchoalveolar lavage fluid than wild-type controls. Furthermore, airway neutrophilia was abolished by a single treatment with neutralizing monoclonal antibody against IL-17 before alpha-GalCer administration. Collectively, our findings reveal that NK1.1(neg) iNKT lymphocytes represent a new population of IL-17-producing cells that can contribute to neutrophil recruitment through preferential IL-17 secretion.

The TLR7 agonist R848 alleviates allergic inflammation by targeting invariant NKT cells to produce IFN-gamma.

It has been documented that TLR7 stimulation triggers not only antiviral responses, but also alleviates experimental asthma. Considering the implication of invariant NKT (iNKT) cells in both situations, we postulated that they might contribute to the anti-inflammatory effect of TLR7 ligands. We show in this study that spleen cells activated by the TLR7 agonist resiquimod (R848) attenuate allergic inflammation upon adoptive transfer when they are recovered from wild-type, but not from iNKT cell-deficient Jα18(-/-) mice, which proves the specific involvement of this regulatory population. Furthermore, we provide evidence that IFN-γ is critical for the protective effect, which is lost when transferred iNKT cells are sorted from IFN-γ-deficient mice. In support of a direct activation of iNKT cells through TLR7 signaling in vivo, we observed a prompt increase of serum IFN-γ levels, associated with upregulation of CD69 expression on iNKT cells. Moreover, we demonstrate that iNKT cells effectively express TLR7 and respond to R848 in vitro by producing high levels of IFN-γ in the presence of IL-12, consistent with the conclusion that their contribution to the alleviation of allergic inflammation upon treatment with TLR7 ligands is mediated through IFN-γ.

Proinflammatory environment dictates the IL-17-producing capacity of human invariant NKT cells.

CD1d-reactive invariant NKT (iNKT) cells have been implicated in a number of experimental models of human pathologies. Given the scope of their immunoregulatory activities mediated through distinct cytokine patterns, it has been proposed that this functional diversity originates from distinct iNKT subpopulations. In this study, we report that human CD161(+) iNKT cells are intrinsically endowed with the capacity to generate IL-17, but require TGF-ß, IL-1ß, and IL-23 to carry out this potential. IL-17-producing iNKT cells are already present in cord blood but, in contrast to peripheral blood iNKT cells, they cannot generate IFN-γ. These IL-17 producers respond to aryl hydrocarbon receptor stimulation and express IL-23 receptor and retinoic acid-related orphan receptor C, similar to conventional T helper 17 cells, from which they differ by their restricted ability to coproduce IL-22. In conclusion, IL-17 production by human iNKT cells depends on two critical parameters, namely an intrinsic program and a proinflammatory environment.

Treatment with the TLR7 agonist R848 induces regulatory T-cell-mediated suppression of established asthma symptoms.

The evolution of allergic asthma is tightly controlled by effector and regulatory cells, as well as cytokines such as IL-10 and/or TGF-ß, and it is widely acknowledged that environmental exposure to allergens and infectious agents can influence these processes. In this context, the recognition of pathogen-associated motifs, which trigger TLR activation pathways, plays a critical role with important consequences for disease progression and outcome. We addressed the question whether the TLR7 ligand resiquimod (R848), which has been shown to be protective in several experimental allergic asthma protocols, can also suppress typical asthma symptoms once the disease is established. To this end, we used an OVA-induced experimental model of murine allergic asthma in which R848 was injected after a series of challenges with aerosolized OVA. We found that the treatment attenuated allergic symptoms through a mechanism that required Tregs, as assessed by the expansion of this population in the lungs of mice having received R848, and the loss of R848-mediated suppression of allergic responses after in vivo Treg depletion. IL-10 provided only a minor contribution to this suppressive effect that was largely mediated through a TGF-ß-dependent pathway, a finding that opens new therapeutic opportunities for the pharmacological targeting of Tregs.

A natural protective function of invariant NKT cells in a mouse model of innate-cell-driven lung inflammation.

Activation of invariant natural killer T (iNKT) cells by treatment with their α-galactosyl ceramide ligand provides therapeutic benefits in several immune inflammatory settings. Given the artificial nature of this stimulation, the natural regulatory functions of iNKT remain uncertain. Addressing this issue in a mouse model of innate-cell-driven lung inflammation induced by the cytokine/alarmin IL-33 that targets iNKT cells, we found that eosinophil and neutrophil recruitment was markedly increased in treated iNKT cell-deficient (Jα18 KO) mice, as was the local production of eotaxin and keratinocyte chemoattractant chemokines. By contrast, lung inflammation decreased after adoptive transfer of iNKT cells, which restored the WT inflammatory response in Jα18 KO mice. Finally, we established that this natural anti-inflammatory function of iNKT cells depends on their IFN-γ production and on endogenous IL-12. Our study provides the first evidence of a protective role of iNKT cells during lung inflammation that does not require pharmacological TCR engagement.

Downregulation of basophil-derived IL-4 and in vivo T(H)2 IgE responses by serotonin and other organic cation transporter 3 ligands.

BACKGROUND: Murine basophils can contribute to the T(H)2 polarization of the immune response by providing rapidly large amounts of IL-4, which suggests that pharmacologic downregulation of this cytokine might provide a strategy to attenuate pathologies associated with excessive production. OBJECTIVE: We examined a number of physiological and pharmacologic ligands of the organic cation transporter 3 (OCT3), a membrane carrier of biogenic amines, for their inhibitory effect on IL-4 production by basophils, selecting the most efficient compounds for in vivo evaluation in basophil-dependent experimental models. METHODS: IL-4 production by basophils isolated ex vivo or from bone marrow cultures was assessed in response to various stimuli with or without biogenic monoamines or pharmacologic analogs. Selected compounds were administered in vivo to examine their effect on levels of circulating IgE generated during a basophil-dependent T(H)2 response and on basophil activation in mice receiving IL-33. RESULTS: We found a drastic decrease in IL-4 production by stimulated basophils on exposure to serotonin (5-hydroxytryptamine [5-HT]) that is taken up by basophils through the specific high-affinity transporters serotonin transporter and the polyspecific, high-capacity organic cation transporter 3 (OCT3; or Slc22a3) but inhibits their function exclusively through the latter. This downregulation is likewise observed in vivo in response to 5-HT and other OCT3 ligands, as well as in human basophils sorted from PMBCs of nonatopic donors. CONCLUSIONS: We provide evidence for a new means of downregulating IL-4 production by basophils, both in vitro and in vivo, through OCT3 targeted by 5-HT and pharmacologic ligands.

Organic cation transporter 3 modulates murine basophil functions by controlling intracellular histamine levels.

In this study, we identify the bidirectional organic cation transporter 3 (OCT3/Slc22a3) as the molecule responsible for histamine uptake by murine basophils. We demonstrate that OCT3 participates in the control of basophil functions because exogenous histamine can inhibit its own synthesis--and that of interleukin (IL)-4, IL-6, and IL-13--through this means of transport. Furthermore, ligands of H3/H4 histamine receptors or OCT3 inhibit histamine uptake, and outward transport of newly synthesized histamine. By doing so, they increase the histamine content of basophils, which explains why they mimic the effect of exogenous histamine. These drugs were no longer effective in histamine-free histidine decarboxylase (HDC)-deficient mice, in contrast with histamine itself. Histamine was not taken up and lost its inhibitory effect in mice deficient for OCT3, which proved its specific involvement. Intracellular histamine levels were increased strongly in IL-3-induced OCT3-/- bone marrow basophils, and explained why they generated fewer cytokines than their wild-type counterpart. Their production was enhanced when histamine synthesis was blocked by the specific HDC inhibitor alpha-fluoro-methyl histidine, and underscored the determinant role of histamine in the inhibitory effect. We postulate that pharmacologic modulation of histamine transport might become instrumental in the control of basophil functions during allergic diseases.

IL-33 activates unprimed murine basophils directly in vitro and induces their in vivo expansion indirectly by promoting hematopoietic growth factor production.

IL-33, a new member of the IL-1 family, has been described as an important inducer of Th2 cytokines and mediator of inflammatory responses. In this study, we demonstrate that murine basophils sorted directly from the bone marrow, without prior exposure to IL-3 or Fc(epsilon)R cross-linking, respond to IL-33 alone by producing substantial amounts of histamine, IL-4, and IL-6. These cells express ST2 constitutively and generate a cytokine profile that differs from their IL-3-induced counterpart by a preferential production of IL-6. In vivo, IL-33 promotes basophil expansion in the bone marrow (BM) through an indirect mechanism of action depending on signaling through the beta(c) chain shared by receptors for IL-3, GM-CSF, and IL-5. IL-3 can still signal through its specific beta(IL-3) chain in these mutant mice, which implies that it is not the unique growth-promoting mediator in this setup, but requires IL-5 and/or GMCSF. Our results support a major role of the latter growth factor, which is readily generated by total BM cells as well as sorted basophils in response to IL-33 along with low amounts of IL-3. Furthermore, GM-CSF amplifies IL-3-induced differentiation of basophils from BM cells, whereas IL-5 that is also generated in vivo, affects neither their functions nor their growth in vitro or in vivo. In conclusion, our data provide the first evidence that IL-33 not only activates unprimed basophils directly, but also promotes their expansion in vivo through induction of GM-CSF and IL-3.

Cutting edge: histamine receptor H4 activation positively regulates in vivo IL-4 and IFN-gamma production by invariant NKT cells.

Histamine (HA) is a biogenic amine with multiple activities in the immune system. In this study we demonstrate that histamine-free histidine decarboxylase-deficient (HDC(-/-)) mice present a numerical and functional deficit in invariant NK T (iNKT) cells as evidenced by a drastic decrease of IL-4 and IFN-gamma production. This deficiency was established both by measuring cytokine levels in the serum and intracellularly among gated iNKT cells. It resulted from the lack of HA, because a single injection of this amine into HDC(-/-) mice sufficed to restore normal IL-4 and IFN-gamma production. HA-induced functional recovery was mediated mainly through the H4 histamine receptor (H4R), as assessed by its abrogation after a single injection of a selective H4R antagonist and the demonstration of a similar iNKT cell deficit in H4R(-/-) mice. Our findings identify a novel function of HA through its H4R and suggest that it might become instrumental in modulating iNKT cell functions.

Critical role of ROR-γt in a new thymic pathway leading to IL-17-producing invariant NKT cell differentiation.

Invariant natural killer T (iNKT) cells constitute a subpopulation of T cells that recognize glycolipids presented by CD1d molecules. They are characterized by their prompt production of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma), which enables them to modulate diverse immune responses. Recently, we enlarged this concept by identifying a distinct IL-17-producing iNKT cell subset, named iNKT17 cells. The mechanisms leading to the acquisition of this new iNKT cell activity are unknown. Herein we show that IL-17-producing iNKT cells are already present in the thymus, predominantly among a subset regarded so far as an immature stage of thymic iNKT cell development, the CD1d tetramer(pos)CD44(pos)NK1.1(neg)CD4(neg) cells. Using EGFP reporter mice, we demonstrate that the transcription factor ROR-gammat is critical for the thymic differentiation of this subset because only ROR-gammat(pos) iNKT cells are capable of massively secreting IL-17. Moreover, IL-17-producing CD1d tetramer(pos)CD44(pos)NK1.1(neg)CD4(neg) thymic iNKT cells have reached a mature differentiation stage because they fail to generate other cell subsets in fetal thymic organ culture. Conversely, thymic ROR-gammat(neg) iNKT cell precursors give rise to progeny, but acquire neither ROR-gammat expression nor the ability to secrete IL-17. In conclusion, our findings demonstrate an alternative thymic pathway leading to the development of iNKT17 cells that requires ROR-gammat expression.

Major T cell progenitor activity in bone marrow-derived spleen colonies.

Common lymphoid progenitors (CLP) are generated in adult bone marrow (BM), but the intermediate steps leading to T cell commitment are unknown, and so is the site at which this commitment occurs. Here, we show that colonies arising in the spleen 12 days after BM injection harbor T cell precursors that are undetectable in BM. These precursors did not generate myeloid cells in vivo but repopulated the thymus and the peripheral T cell compartment much faster than did CLP. Two lineage negative (Lin(-)) subpopulations were distinguished, namely CD44(+) Thy1(-) cells still capable of natural killer generation and transient low-level B cell generation, and T cell-restricted CD44(-) Thy1(+) cells. At a molecular level, frequency of CD3epsilon and preTalpha mRNA was very different in each subset. Furthermore, only the CD44(-) Thy1(+) subset have initiated rearrangements in the T cell receptor beta locus. Thus, this study identifies extramedullary T cell progenitors and will allow easy approach to T cell commitment studies.

The pro-Th2 cytokine IL-33 directly interacts with invariant NKT and NK cells to induce IFN-gamma production.

IL-33 has recently been identified as a cytokine endowed with pro-Th2 functions, raising the question of its effect on invariant natural killer T cell (iNKT), which are potent IL-4 producers. Here, we report a two-fold increase of iNKT-cell counts in spleen and liver after a 7-day treatment of mice with IL-33, which results from a direct effect, given that purified iNKT cells express the T1/ST2 receptor constitutively and respond to IL-33 by in vitro expansion and functional activation. Conversely to the expected pro-Th2 effect, IL-33 induced a preferential increase in IFN-gamma rather than IL-4 production upon TCR engagement that depended on endogenous IL-12. Moreover, in combination with the pro-inflammatory cytokine IL-12, IL-33 enhanced IFN-gamma production by both iNKT and NK cells. Taken together these data support the conclusion that IL-33 can contribute as a co-stimulatory factor to innate cellular immune responses.

Role of GM-CSF in tolerance induction by mobilized hematopoietic progenitors.

Mechanisms of protection against autoimmune diseases by transplantation of autologous hematopoietic progenitors remain poorly defined. We recently demonstrated that, unlike medullary hematopoietic stem cells (HSCs), mobilized hematopoietic progenitors (HPCs) stimulate peripheral Foxp3(+) regulatory T cell (Treg)-expansion through cell-contact activation of Notch signaling and through as yet undetermined soluble factor(s), distinct from TGF-beta1. Herein we identified one such soluble factor as granulocyte macrophage-colony stimulating factor (GM-CSF), which is produced at higher levels by HPCs than HSCs and whose neutralization significantly reduces the growth-promoting effect of HPCs on Treg. Treg express a functional GM-CSF receptor alpha-chain CD116 and proliferate in response to this cytokine independently from IL2. GM-CSF-expanded Treg-like HPC-expanded Treg-display enhanced suppressive capacity relative to control Treg. Hence, mobilized progenitors stimulate Treg expansion both by cell-contact dependent mechanisms and by their production of GM-CSF.

Adhesion of renal carcinoma cells to endothelial cells depends on PKCmu.

BACKGROUND: The formation of metastases includes the separation of tumor cells from the primary tumor, cell migration into subendothelial tissue and cell proliferation in secondary organ. In this process, cell adhesion of tumor cells to the endothelium is an essential requirement for formation of metastases. Protein kinase C (PKC) regulates adhesion and proliferation. To identify a relation between PKC isoforms and tumor progression in renal cell carcinoma (RCC), the influence of PKC isoforms on cell adhesion and proliferation, and possible influences of integrins were analyzed in RCC cells. METHODS: The experiments were performed in the RCC cell lines CCF-RC1 and CCF-RC2 after pre-incubation (16 h) with the PKC inhibitors GF109203X (inhibits PKCalpha, betaI, betaII, gamma, delta and epsilon), GO6976 (inhibits PKCalpha, betaI and mu), RO31-8220 (inhibits PKCalpha, betaI, betaII, gamma and epsilon) and rottlerin (inhibits PKCdelta). Cell adhesion was assessed through adherence of RCC cells to an endothelial monolayer. Cell proliferation was analyzed by a BrdU incorporation assay. The expression of beta1 integrins was analyzed by flow cytometry. RESULTS: In CCF-RC1 cells, cell adhesion was significantly reduced by GO6976 to 55% and by RO31-8220 to 45% of control. In CCF-RC2 cells, only GO6976 induced a significant reduction of cell adhesion to 50% of control levels. Proliferation of both cell lines was reduced by rottlerin to 39% and 45% of control, respectively. The beta1 integrin expression on the cell surface of CCF-RC1 and CCR-RC2 cells was decreased by RO31-8220 to 8% and 7% of control, respectively. beta2 and beta3 integrins were undetectable in both cell lines. CONCLUSIONS: The combination of the PKC inhibitors leads to the assumption that PKCmu influences cell adhesion in CCF-RC1 and CCF-RC2 cells, whereas in CCF-RC1 cells PKCepsilon also seems to be involved in this process. The expression of beta1 integrins appears to be regulated in particular by PKCepsilon. Cell proliferation was inhibited by rottlerin, so that PKCdelta might be involved in cell proliferation in these cells.

Histamine, immune cells and autoimmunity.

Histamine is one ofthe most versatile biogenic amines with multiple roles during the immune response and in allergic disorders. With four distinct G protein-coupled receptors (H1R, HER, H3R and H4R), intracellular histamine binding sites (most likely members of the cytochrome P450 family) as well as a membrane transporter (Organic Cation Transporter; OCT3) expressed in various immunocompetent cells, it can entertain a complex network of interactions. These signaling pathways are expressed differentially, depending on the stage of differentiation or activation of target cells, thus adding a further degree of complexity to the system. For this reason, published data are sometimes conflicting and varying according to the particular cell type or responses analyzed and the experimental approaches used. On the other hand, histamine is generated by several cells during the immune response, not only through release of intracellular stores in mast cells or basophils in response to IgE-dependent or -independent stimuli, but also through neosynthesis catalyzed by histidine decarboxylase (HDC) in a number ofhematopoietic cells that secrete the amine immediately without prior storage. These features enable histamine to tune the fine balance between immunity and tolerance by affecting dendritic cells, immunoregulatory cells, T-cell polarization and cytokine production, making the way for new pharmacological strategies to control immune reactivity during immune disorders, such as autoimmunity.

Human bone marrow adipocytes block granulopoiesis through neuropilin-1-induced granulocyte colony-stimulating factor inhibition.

Adipocytes are part of hematopoietic microenvironment, even though up to now in humans, their role in hematopoiesis is still questioned. We have previously shown that accumulation of fat cells in femoral bone marrow (BM) coincides with increased expression of neuropilin-1 (NP-1), while it is weakly expressed in hematopoietic iliac crest BM. Starting from this observation, we postulated that adipocytes might exert a negative effect on hematopoiesis mediated through NP-1. To test this hypothesis, we set up BM adipocytes differentiated into fibroblast-like fat cells (FLFC), which share the major characteristics of primitive unilocular fat cells, as an experimental model. As expected, FLFCs constitutively produced macrophage colony stimulating factor and induced CD34(+) differentiation into macrophages independently of cell-to-cell contact. By contrast, granulopoiesis was hampered by cell-to-cell contact but could be restored in transwell culture conditions, together with granulocyte colony stimulating factor production. Both functions were also recovered when FLFCs cultured in contact with CD34(+) cells were treated with an antibody neutralizing NP-1, which proved its critical implication in contact inhibition. An inflammatory cytokine such as interleukin-1 beta or dexamethasone modulates FLFC properties to restore granulopoiesis. Our data provide the first evidence that primary adipocytes exert regulatory functions during hematopoiesis that might be implicated in some pathological processes. Disclosure of potential conflicts of interest is found at the end of this article.