Macrophages are key regulatory cells of fibrogenesis. They can have pro- or antifibrotic activity due to their plasticity and heterogeneity. Some studies have shown the antifibrotic effect of macrophages on dermal fibroblasts, but the effect of macrophages on the lung fibroblast functions remains unexplored. Therefore, the purpose of this study was to examine the influence of conditioned media of human macrophage differentiated by M-CSF/GM-CSF and further dexamethasone polarized/unpolarized on the TGF-β-induced lung fibroblast differentiation. Macrophages were derived from peripheral blood monocytes of healthy donors. Monocytes were differentiated by M-CSF or GM-CSF for 7 days. On day 5, dexamethasone was added to generation of polarized macrophages M-M(Dex) and GM-M(Dex). Polarized macrophages were compared with non-polarized M-M0 and GM-M0, to which dexamethasone was not added. Next, the conditioned medium of these macrophage subtypes was collected and tested for inhibition the lung fibroblast differentiation (HLF210 cell line). To do this, TGF-β (inducing differentiation factor) and conditioned macrophage medium were added to fibroblast cultures. Effectiveness of differentiation was estimated by the expression of the myofibroblast marker, α-smooth muscle actin (α-SMA), and the production of extracellular matrix protein, collagen I. The expression of α-SMA was determined using flow cytometry. The concentration of collagen I was measured by ELISA. Since our data indicates that spontaneous activation of fibroblasts occurs during standard cultivation, the α-SMA expression was investigated in 3D culture of fibroblasts. Notably, the content of α-SMA-positive cells in 3D cultures was significantly reduced, indicating more physiological growth cells. Regardless of the differentiation stimulus, the conditioned media of dexamethasone-polarized macrophages do not affect the level of collagen I production or the α-SMA expression. On the contrary, M-M0 showed a strong inhibitory effect that reduced the amount of collagen I in the fibroblast cultures and the expression of marker myofibroblasts by fibroblasts. Interesting, GM-M0 had no such effect and did not prevent lung fibroblast differentiation like polarized cells. Taken together, the findings suggest that M-M0 macrophages may have antifibrotic properties. Furthermore, the lack of this effect in GM-M0 macrophages indicates that the differentiation factor plays a significant role in the development of the antifibrotic macrophage phenotype.

Macrophages are involved in the regulation of fibrogenesis and turnover of the extracellular matrix. One way to perform this function is through the production of profibrotic and fibrolytic factors including fibronectin, laminin, collagen, and extracellular matrix proteases. The production of most of them has been well studied in experimental models; however, much remains unclear regarding human macrophages. Therefore, the aim of this study was to study the content of extracellular matrix proteases (MMP-2 and MMP-9, cathepsin L), their inhibitors (TIMP-1), and collagen (type I) in supernatants of differently activated human macrophages. We compared macrophages differentiated by M-CSF or GM-CSF and further polarized in M1 with lipopolysaccharide, in M2a with IL-4, and in M2c with dexamethasone. Macrophages was obtained from peripheral blood monocytes. The content of MMPs, TIMP, cathepsin, and collagen was determined using appropriate ELISA kits. The results obtained demonstrate that differentiation factors are more important for the production of the above factors compared to polarizing stimuli (lipopolysaccharide, IL-4, dexamethasone). Moreover, macrophages differentiated by M-CSF showed predominantly antifibrotic activity because of pronounced MMPs production, while GM-CSF-induced cultures, on the contrary, were characterized by profibrotic properties due to the high level of TIMP-1 and type I collagen. M1, M2a, and M2c, induced by M-CSF, differed only in MMP-2 production, and M2a produced this metalloproteinase more than other subtypes. In the case of GM-CSF-differentiated cells, a higher level of production of TIMP-1 and, to a lesser extent, type I collagen was characteristic of M1, whereas M2c have minimal concentration of them among GM-CSF-induced macrophage subtypes. Concerning the level of cathepsin L production was relatively constant and did not depend on the generation conditions (differentiation and polarizing signals). Thus, the data obtained help to identify macrophage subtypes with anti- or profibrotic potential and may be useful for the development of cell therapy for diseases associated with fibrogenesis dysregulation.

During pregnancy, the maternal immune system must maintain tolerance to paternal antigens, at the same time being able to eliminate pathogens, which is achieved by the weakening of adoptive immunity and the activation of innate immunity, in particular, monocytes. However, the question about the functional phenotype of monocytes, having not only pro-inflammatory, but also anti-inflammatory activity, remains open. In the given work, we have investigated the expression of M2-associated suppressive markers Arg1 and MerTK in monocyte subpopulations during uncomplicated pregnancy. Fifty-three pregnant women with uncomplicated gestation were recruited, including 14 pregnant in the 1st trimester, 20 – in the 2nd and 19 – in the third pregnancy trimester. The comparison group consisted of 15 fertile unpregnant women without aggravated somatic anamnesis, with a history of at least one childbirth. The findings showed that in the unpregnant group circulating Mo express Arg1 and MerTK, and the most relative number of Arg1+ and MerTK+ cells is concentrated in intermediate and nonclassic monocytes. During pregnancy the expression of researched molecules in monocytes reliably increases. An increase in MerTK expression is manifested by a simultaneous increase in the number of MerTK+ cells and the mean fluorescence intensity of this marker; it is observed in the 1st and 2nd trimesters and registered in all three monocyte subpopulations. At the same time, an increase in Arg1 expression is manifested either by an enhancement of Arg1+ cells, or an increase in receptor density; it is registered throughout pregnancy, including the 3rd trimester, and is maximally expressed in classic monocytes. There is a direct correlation between the number of Arg1+ and MerTK+ cells in intermediate Mo, which increases with the progression of pregnancy, and in the 3rd trimester is also detected in classical and non-classical Mo. In general, the revealed increase in the expression of Arg1 and MerTK by monocytes indicates an increase in the anti-inflammatory potential of monocytes during pregnancy, and the involvement of monocytes in the regulation of the inflammatory process at the system level. Moreover, the features of Arg1 and MerTK expression in various monocyte subpopulations during pregnancy suggest that monocytes expressing Arg1 and MerTK can mediate different mechanisms of immune adaptation during pregnancy.

GM-CSF and M-CSF, the hematopoietic colony-stimulating factors, induce various phenotypic changes in macrophage lineage populations and promote cell differentiation, respectively, into M1- and M2-like macrophages. The pro- and anti-inflammatory properties of macrophages generated by these colony-stimulating factors are well described, but the contribution of differentiation and polarization signals to the fibromodulatory activity of macrophages remains unexplored. To clarify the differences in the fibrogenesis regulation mechanisms inherent in differently activated macrophages, we studied the effects of macrophage-conditioned media on proliferation and differentiation of dermal fibroblasts. In this study, the human macrophages generated from peripheral blood monocytes were investigated. They were induced for differentiation by M-CSF or GM-CSF, being further polarized in the M1 direction with lipopolysaccharide and, in the M2 direction, with IL-4 or dexamethasone. Proliferative response of the fibroblasts was determined radiometrically by [3H]-thymidine incorporation. Differentiation into myofibroblasts was determined with flow cytometry technique, as expression of a specific marker α-smooth muscle actin (α-SMA). The level of macrophage TGF-β1 production was assessed using an appropriate ELISA kit. The data obtained indicate that the macrophages differentiated under the influence of “homeostatic” M-CSF are characterized by a moderate stimulating effect upon fibroblast proliferation, and the effects of M2 (IL-4) and M2 (Dex) macrophages exceed that of M1 (LPS), but do not differ significantly from each other. The M-CSF-induced M1 (LPS) and M2 (IL-4) macrophages, but not M2 (Dex), enhance the fibroblast differentiation and show similar level of stimulation. In contrast to M-CSF, the macrophages induced by “pro-inflammatory” GM-CSF exhibit a pronounced stimulatory effect on fibroblast proliferation, and the effects of M2 macrophages exceed those of M1 cells, being most pronounced for M2 (Dex). At the same time, only GM-CSF-induced M2 (IL-4) macrophages enhance fibroblast differentiation. Dexamethasone-polarized macrophages do not significantly affect fibroblast differentiation regardless of the CSF used (M-CSF or GM-CSF). The content of TGF-β1 in the supernatants of differently activated macrophages does not correlate with the level of stimulating effect of macrophage-conditioned media upon fibroblast differentiation. In general, the data obtained suggest the involvement of differentiation and polarization signals into modulation of pro- and anti-fibrogenic properties of macrophages.

We studied the effect of conditioned media of GM-CSF-differentiated human macrophages polarized in M1(LPS), M2a(IL-4), M2c(dexamethasone), and M2(low serum) phenotypes on proliferation, differentiation, and collagen-producing activity of dermal fibroblasts. It was found that M1(LPS) and M2a(IL-4) were characterized by moderate influence on functional activity of fibroblasts. At the same time, soluble factors of M2c(dexamethasone) significantly enhanced the proliferative response of fibroblasts, but not their differentiation and type I collagen production. On the contrary, M2(low serum) generated under conditions of growth factors deficiency had a pronounced stimulating effect on the differentiation of fibroblasts and production of type I collagen by these cells, but moderately stimulated the fibroblast proliferation. Thus, the secretory activity of various functional phenotypes of macrophages is an important mechanism of fibrogenesis regulation.

We studied the expression of arginase-1 (Arg1) and tyrosine kinase Mer (MerTK) in GMCSF-differentiated human macrophage populations М0, М1(IFNγ), М2а(IL-4), and М2(low serum) generated under conditions of growth/serum factor deficiency. The maximum relative content of Arg1+ and MerTK+ cells was found in М2 macrophage populations: М2а(IL-4) and М2(low serum). As the uptake of apoptotic cells is the key mechanism of M2 polarization during M2(low serum) generation, we performed a special series of experiments and showed that incubation with allogeneic apoptotic neutrophils significantly increased the percentages of CD206+ macrophages co-expressing Arg1 and MerTK.

Macrophages play the key role in the regulation of neuroregeneration. For evaluation of the neuroregenerative potential of M2 macrophages, we studied the effect of macrophages polarized with IL-4 (M2a (IL-4)) and by efferocytosis under conditions of serum deprivation (LS, Low Serum; M2(LS)) on proliferative activity and apoptosis of SH-SY5Y cells under conditions of deficiency of growth/serum factors. Conditioned media of both M2(LS) and M2a(IL-4) stimulated proliferation of SH-SY5Y cells. Moreover, soluble factors of M2(LS) and M2a(IL-4) reduced the degree of early apoptosis of SH-SY5Y cells and the protective effect of M2(LS) was observed at earlier terms of culturing. Our findings suggest that M2 macrophages have high neuroregenerative potential that is mediated through soluble factors and manifests itself both in stimulation of proliferation and inhibition of apoptosis of SH-SY5Y cells.

The study investigated the effect of conditioned media of M1 and M2 macrophages on the phenotype and proliferation of the human neuroblastoma cell line SH-SY5Y. It has been established that conditioned media of M2 macrophages, generated in the presence of GM-CSF under defi ciency of growth factors, have a pronounced stimulating effect on the SH-SY5Y cell proliferation. The expression of the low-affinity nerve growth factor receptor, CD271, correlates with cell morphology: in cultures with a predominance of N-type cells, the number of CD271+ cells is signifi cantly higher compared to cultures dominated by S-type cells.

Peripheral blood monocytes are heterogeneous CD14+ cell population, some of which also express CD16 molecule. Differences in phenotype between monocyte subpopulations can affect their functional activity, as well as the ability to further differentiate into dendritic cells (DCs). DCs are professional antigen-presenting cells which induce the immune response or, conversely, maintain the immunological tolerance. The aim of the present study was to analyze the relationship between monocyte subpopulations and the functional activity of monocyte-derived DCs, as well as DC sensitivity to the tolerogenic effect of dexamethasone. DCs were generated by cultivating enriched fractions of CD14+ monocytes with or without CD16+ cell depletion (CD16-Mo-DCs or CD16+Mo-DCs, respectively) in the presence of IFNα and GM-CSF. Monocyte subpopulations were obtained by immunomagnetic negative selection. CD16+Mo-DCs were characterized by lower ability to take up FITC-dextran and higher allostimulatory activity compared to CD16-Mo-DCs. In addition, CD16+Mo-DCs showed higher apoptosis-inducing activity against autologous CD4+T lymphocytes and allogeneic CD8+T lymphocytes, but were similar to CD16-Mo-DCs in their ability to induce apoptosis in allogeneic CD4+T lymphocytes. TNFa production level, similar for both types of DCs, was negatively correlated with CD16-Mo-DC allostimulatory activity and directly correlated with apoptosis-inducing activity of CD16+Mo-DCs towards allogeneic CD4+T cells. CD16-Mo-DCs and CD16+Mo-DCs were similar by their IL-10 production, which was inversely related to allostimulatory activity of both types of DCs. Dexamethasone increased endocytic activity, decreased the ability to stimulate autologous and allogeneic T cells, inhibited TNFα production of CD16-Mo-DCs and CD16+Mo-DCs. However, CD16+Mo-DCs demonstrated a more pronounced increase in endocytic activity and more dramatic decrease in their ability to stimulate the proliferation of CD4+T cells in auto-MLR. Also, addition of dexamethasone into CD16+Mo-DCs cultures led to the increase in DC pro-apoptogenic activity against autologous CD8+T lymphocytes. Thus, the presence of CD16+ cells among monocyte population affects the properties of IFNα-induced monocyte-derived DCs and DC sensitivity to the immunomodulatory effects of dexamethasone.

Macrophages (Mφ) play a key role in regulation of fibrogenesis, including proliferation of fibroblasts and myofibroblasts, differentiation of progenitor cells into myofibroblasts, as well as synthesis and secretion of the extracellular matrix, mainly collagen. The direction of the Mφ effects (stimulation or suppression) is determined by a number of factors, including the stage of the fibrotic process and the Mφ functional phenotype dependent on the signals of microenvironment. One of the feasible ways of the fibrogenesis regulating is the secretion of pro- or antifibrotic factors such as matrix metalloproteinases, inhibitors of metalloproteinases and some cytokines. However, existing data on ability to secrete these factors by various subpopulations of human Mφ are rare and controversial. The aim of this study was to characterize the ability of human M1, M2a, and M2c Mφ differentiating in the presence of GM-CSF to produce matrix metalloproteinases (MMP-9) and their tissue inhibitors (TIMP-1), as well as some cytokines and growth factors. As compared to M2 macrophages, the M1 macrophages polarized by lipopolysaccharide produced significantly more TNFα, IL-6 and IL-2 that have pro-inflammatory activity and are able to initiate a fibrotic process. In turn, M2a Mφ stimulated by IL-4 were characterized by a high level of VEGF production and, at the same time, low levels of TNFα and IL-6, which may determine the important role of these cells at the proliferative stage of fibrosis and stimulation of extracellular matrix deposition. Finally, M2c Mφ polarized by dexamethasone, exhibited the М2а-like cytokine profile, i.e., VEGF was actively produced against the background of low TNFα and IL-6 synthesis. Moreover, all three Mφ subpopulations did actively secrete MMP-9 and TIMP-1, without significant difference in production of these factors. However, M2c Mφ differed by a significantly higher MMP-9/TIMP-1 ratio index compared to M1 and M2a Mφ, and it is crucial at the rearrangement stage of the fibrotic process. Thus, the production of MMP-9 and TIMP-1, together with other pleiotropic cytokines and growth factors by various Mφ subtypes may reflect their role in regulation of fibrotic process at various stages.

The paper presents a comparative characterization of the MMP-9 and TIMP-1 production by various subsets of macrophages (Mφ) differentiated in the presence of GM-CSF and polarized into M1, M2a and M2c cells. It was shown that all the studied Mφ subtypes produced both MMP-9 and TIMP-1. At the same time, the MMP-9 / TIMP-1 ratio was signifi cantly higher in M2c Mφ compared to M1 and M2a, which may indicate the important role of M2c macrophages during tissue remodeling and restriction of fibrosis.

The aim of the study was to analyze the relationship between monocyte subpopulations and phenotype/ functions of monocyte-derived dendritic cells (DCs), as well as DC sensitivity to the tolerogenic effect of dexamethasone. Materials and methods. The study included 15 healthy donors. DCs were generated by cultivating enriched fractions of CD14+ monocytes with or without CD16+cell depletion (CD16-Mo-DCs or CD16+Mo-DCs, respectively) in the presence of interferon alpha (IFNα) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Monocyte subpopulations were obtained by immunomagnetic negative selection. Results. CD16+Mo-DCs were characterized by higher percentage of mature (CD83+CD14-) and lower number of semi-mature (CD14+CD83+) cells, but were similar to CD16-Mo-DCs by HLA-DR and CD86 expression, involved in the presentation of antigens and activation of naive T-cells. and also to co-inhibitory/ tolerogenic molecules B7-H1 and TLR-2. CD16+Mo-DCs displayed higher allostimulatory activity, which was positively correlated with CD86 expression ( rS = 0.69; p = 0.027) and negatively – with TLR-2 expression ( rS = -0.72; p = 0.1). Allostimulatory activity of CD16-Mo-DCs was positively correlated with the number of mature CD14-CD83+DCs and semi-mature CD14+CD83+DCs. Addition of dexamethasone (10-6 M) into CD16-Mo-DCs and CD16+Mo-DCs cultures led to the delay of DC maturation, the decrease of CD86 and the increase of TLR-2 expression, as well as the increase of cells with co-inhibitory CD86- B7-H1+ phenotype that was positively correlated with the reduction of DC allostimulatory activity. The decrease of CD86+/TLR-2+ index in CD16+Mo-DC population was due to the reduction of CD86+DCs and in CD16-Mo-DC population – to the increase of TLR-2+cells. Dexamethasone possessed higher inhibitory effect on DC maturation in the CD16+Mo-DC cultures. Conclusion. CD14+ monocytes, both contained and depleted by CD16+ cells, can differentiate into DCs when cultured with IFNα. The presence of CD16+ cells in whole blood monocyte pool is associated with generation of DCs showed a more mature phenotype and higher allostimulatory activity. Both CD16- and CD16+ monocyte-derived DCs are sensitive to suppressive effect of dexamethasone. However, dexamethasone tolerogenic effect involves different mechanisms in CD16-Mo-DCs and CD16+Mo-DCs.

We studied the effect of apoptotic neutrophils on the production of erythropoietin, MMP-9, and TIMP-1 by GM-CSF-induced human macrophages. GM-CSF-induced macrophages spontaneously produce erythropoietin and secrete MMP-9 and TIMP-1. Polarization of these macrophages towards the M2-like phenotype after exposure to apoptotic neutrophils considerably increased the production of erythropoietin; the MMP-9/TIMP-1 ratio tended to increase under these conditions due to a decrease in TIMP-1.

The functional phenotype of macrophages (Mφ) is determined by both differentiation factors and polarization stimuli. In mouse Mφ could be easily divided into the distinct Mφ subtypes. However, the identification of human M1 and M2 cells is much more difficult due to the lack of M1- or M2-specific markers. We assumed that the Mφ capacity to induce T cell proliferation in mixed leukocyte culture, or allostimulatory activity, may be a marker of Mφ functional phenotype. We compared the allostimulatory activity of Mφ differentiated with GM-CSF or M-CSF and polarized into M1, M2a, M2c subtypes using appropriate stimuli. GM-CSF-differentiated M1 Mφ showed pronounced allostimulatory activity whereas the polarization into M2a and M2c of GM-CSF-differentiated Mφ was associated with decreased allostimulatory activity. M-CSF-differentiated M1 Mφ demonstrated the moderate increasing of allostimulatory activity but its level has never reached that of GM-CSF-activated M1. The level of allostimulatory activity of M2a and M2c M-CSF-induced Mφ was comparable to that of GM-CSF-induced M2a and M2c Mφ. Thus, low allostimulatory activity is a common property of human M2a and M2c macrophages regardless of the differentiating factor and a polarizing stimulus and can be used to distinguish between M1 and M2 phenotypes.

Objective. Mesenchymal stromal cells (MSCs) promote the differentiation of unprimed macrophages (Mр) or classically activated M1 cells towards alternatively activated, M2 macrophages. The aim of the work was to study the ability of MSC to induce M1→M2 switching by comparing the MSC effects on polarized M1 macrophages and monocytes stimulated by granulocyte-macrophage colony-stimulating factor to M1 differentiation.Material and мethods. MSC were co-cultured with monocytes for 7 days or M1 macrophages for 48 hours in Transwell system to prevent direct cell-to-cell contacts. To characterize generated Mр, classical M2 marker CD206, allostimulatory activity in a mixed lymphocyte culture (MLC), and the ability to secrete pro-/antiinflammatory mediators were analyzed.Results. Co-cultivation of MSCs and M1 macrophages led to the appearance of phenotypic (increased expression of CD206) and functional (decrease in allostimulatory activity) features of M2 phenotype. When MSCs were cultured with monocytes in the M1-inducing medium, generated Mр elicited a pronounced stimulating activity in MLC similar to that of M1 (stimulation index 3.45 and 3.4, p = 0.46) and significantly higher than allostimulatory activity of M2 cells (3.45 vs 2.2, p = 0.03). In addition, MSCs did not influence the expression of CD206, as well as the production of pro- (IL-1β, TNF-α, IL-6, IL-12) and anti-inflammatory (IL1-ra, IL-4, IL-10) cytokines, immunoregulatory cytokines (IFN-γ, IL-17) and chemokines (IP-10, MCP-1, MIP-1b, Rantes, Eotaxin).Conclusions: The ability of MSC to induce the M2 phenotype depends on the stage of differentiation of monocyte/macrophages. MSCs promote M1→M2 switching in cultures of polarized M1 macrophages. In contrast, when MSCs interacted with monocytes in M1-inducing medium, a population of M1-like macrophages is formed with high allostimulatory activity and typical for M1 spectrum of produced cytokines and chemokines.

The aim of present study was to evaluate safety and clinical efficacy of inhalatory immunotherapy based on intranasal delivery of bioactive factors produced by M2 macrophages applied for treatment of patients with organic brain syndrome (OBS).Materials and methods. The study under the NCT02957123 protocol (www.ClinicalTrails.gov) included thirty patients with OBS of various genesis (10 men and 20 women aged 18 to 81; Me, 62.5 years). Neurological assessment and the levels of 32 cytokines in the blood serum of patients were evaluated before and 2-3 days after completion of inhalation immunotherapy.Intranasal inhalations of cell-free culture medium of M2 macrophages (2 mL, once a day for 28-30 days) were safe and well tolerated. None of 30 treated patients had severe adverse events and serious treatmentrelated side reactions. One month after starting the inhalations, a positive dynamics in neurological status was noted in all the patients. A marked clinical response was documented in twenty out of thirty patients (67%), which manifested as improvement, according to all scales and questionnaires. The neurological improvement was not reversed over 6 months of follow-up period. In other ten patients (33%), a moderate clinical response was shown as improvement of individual scores. The positive changes were as follows: 1) a 43% decrease in anxiety and depression scores (according to HADS scale, pU = 0.0008); 2) an increase of total motor activity (stability and gait) by 25%, pU = 0.0001); 3) correction of cognitive functions (MoCa test, pU = 0.007); 4) reduced number and intensity of the disease symptoms by 52% (pU = 0.0001). This marked clinical response to immunotherapy is shown to be associated with correction/normalization of serum hepatocyte growth factor (HGF) level.Conclusion. Inhalation immunotherapy based on intranasal delivery of bioactive factors produced by M2 macrophages can improve neurological and functional recovery in patients with organic brain syndrome.

The engulfment of apoptotic cells by monocytes and unprimed macrophages results in M2 polarization. In the current study, we investigated whether apoptotic cells influence the phenotypic and functional characteristics of GM-CSF-differentiated human macrophages (GM-Mφ). Our results demonstrate that GM-Mφ preincubated with apoptotic neutrophils (GM-MφNeu) show significantly increased expression of CD206 and FasL and decreased capacity to stimulate allogeneic T-cell proliferation thus adopting M2 features. The 27-plex analysis demonstrates the down-regulation of 24 cytokines (including IL-10) in GM-MφNeu cultures. In contrast, apoptotic neutrophils enhance PGE2 synthesis by GM-Mφ, and blocking PGE2 production with indomethacin restores an allostimulatory activity of GM-MφNeu. These data provide evidence that GM-Mφ following exposure to apoptotic cells acquire features of M2 cells. Given the global suppression of cytokine secretion, GM-MφNeu resemble deactivated (M2c) macrophages, and their capacity to inhibit allogeneic T-cell proliferation appears to be mediated by an enhanced synthesis of PGE2 but not IL-10.

The effects of anti-CD208 antibodies (mannose receptor) on functional characteristics of peritoneal macrophages were studied in intact mice and mice with lipidemia induced by poloxamer-407. Lipidemia was associated with suppression of phagocytosis and increase in spontaneous proliferative potential and NO production by macrophages. Anti-CD206 antibodies suppressed NO production by macrophages in mice with lipidemia.

The phenotypic and functional features of human M2 macrophages, in particular, their immunosuppressive activity, can considerably vary depending on M2 polarizing stimulus. This study was aimed at the investigation of cytokine production and pro‐apoptogenic/inhibitory molecule expression in macrophages generated with GM ‐ CSF using either standard conditions (M1) or deficiency of serum/growth factors (M2‐ LS cells). In contrast to M1, M2‐ LS cells were characterized by an enhanced content of CD 206 + , B7‐H1 + , FasL + and TRAIL + cells along with a decreased production of IFN ‐ γ , IL ‐5, IL ‐6, IL ‐13, TNF ‐ α , IL ‐17 and MCP ‐1. In addition, M2‐ LS exhibited a lower T cell stimulatory activity in MLC that was associated with the higher numbers of apoptotic and the lower numbers of proliferating T cells. B7‐H1 plays a key role in M2‐ LS ‐mediated cytotoxic effects as the neutralization of B7‐H1 reduces the apoptosis‐inducing activity of M2‐ LS , while the blocking of CD 206 and TRAIL reduces the cytostatic activity of M2 macrophages.