Schistosoma japonicum infection induces macrophage polarization

The role of macrophages （MФ） as the first line of host defense is well accepted. These cells play a central role in orchestrating crucial functions during schistosomal infection. Thus, understanding the functional diversity of these cells in the process of infection as well as the mechanisms underlying these events is crucial for developing disease control strategies. In this study, we adopted a Mqb polarization recognition system. M1 macrophage was characterized by expressing CD16/32, IL-12 and iNOS. M2 macrophage was characterized by expressing CD206, IL-10 and arg-1. In vivo （mouse peritoneal macrophages of different infection stages were obtained） and in vitro （different S. japonicum antigens were used to stimulate RAW264.7） were characterized by using the above mentioned system. NCA and ACA stimulated RAW264.7 express significantly higher levels of IL-12 while significantly higher levels of IL-10 were detected after soluble egg antigen （SEA） stimulation. The results showed that dramatic changes of antigen in the microenvironment before and after egg production led to macrophage polarization. Furthermore, through TLR blocking experiments, the TLR4 signaling pathway was found to play a role in the process of macrophage polarization toward M1. Our data suggest that macrophage polarization during S. japonicum infection had significant effects on host immune responses to S. japonicum.     

Heme Oxygenase-1 expression in M-CSF-polarized M2 macrophages contributes to LPS-induced IL-10 release

The shift between pro-inflammatory (M1) and anti-inflammatory (M2) states of macrophage polarization allows the resolution of inflammatory processes as well as the maintenance of a basal anti-inflammatory environment in tissues continuously exposed to harmless antigens (e.g., lung and gut). To identify markers for the anti-inflammatory state of macrophages, expression profiling was performed on human macrophages polarized by either GM-CSF or M-CSF, which lead to the generation of TNF-α and IL-12p40-producing pro-inflammatory macrophages [M1 (GM-CSF)] or IL-10-producing anti-inflammatory macrophages [M2 (M-CSF)] upon exposure to LPS, respectively. A different iron metabolism gene signature was detected in both macrophage types, with the heme regulatory molecules CD163 and Heme Oxygenase-1 (HO-1) being preferentially expressed by M2 (M-CSF) macrophages. M1-polarizing cytokines (GM-CSF, IFNγ) inhibited, while IL-4 enhanced, the M-CSF-driven HO-1 expression. In agreement with this in vitro data, HO-1 expression in metastatic melanoma was primarily detected in CD163⁺ tumor-associated macrophages, which are known to exhibit an M2-skewed polarization phenotype. In contrast to the HO-1 inhibitor tin protoporphyrin (SnPP), the administration of cobalt protoporphyrin (CoPP), a potent inducer of HO-1 resulted in increased LPS-triggered IL-10 release from M2 (M-CSF) macrophages. The data suggests that HO-1 is important for the anti-inflammatory activities of M-CSF-polarized M2 macrophages. Moreover, since M2 (M-CSF) macrophages also express higher levels of the CD163 scavenger receptor, the CD163/HO-1/IL-10 axis appears to contribute to the generation of an immunosuppressive environment within the tumor stroma.     

Toll-Like Receptor 2-Dependent Extracellular Signal-Regulated Kinase Signaling in Mycobacterium tuberculosis-Infected Macrophages Drives Anti-Inflammatory Responses and Inhibits Th1 Polarization of Responding T Cells

Mycobacterium tuberculosis survives within macrophages and employs immune evasion mechanisms to persist in the host. Protective T helper type 1 (Th1) responses are induced, and the immune response in most individuals is sufficient to restrict M. tuberculosis to latent infection, but most infections are not completely resolved. As T cells and macrophages respond, a balance is established between protective Th1-associated and other proinflammatory cytokines, such as interleukin-12 (IL-12), interferon gamma (IFN-γ), and tumor necrosis factor alpha, and anti-inflammatory cytokines, such as IL-10. The mechanisms by which M. tuberculosis modulates host responses to promote its survival remain unclear. In these studies, we demonstrate that M. tuberculosis induction of IL-10, suppression of IL-12, and inhibition of class II major histocompatibility complex (MHC-II) molecules in infected macrophages are all driven by Toll-like receptor 2 (TLR2)-dependent activation of the extracellular signal-regulated kinases (ERK). Elimination of ERK signaling downstream of TLR2 by pharmacologic inhibition with U0126 or genetic deletion of Tpl2 blocks IL-10 secretion and enhances IL-12 p70 secretion. We demonstrate that M. tuberculosis regulation of these pathways in macrophages affects T cell responses to infected macrophages. Thus, genetic blockade of the ERK pathway in Tpl2^−/− macrophages enhances Th1 polarization and IFN-γ production by antigen-specific CD4⁺ T cells responding to M. tuberculosis infection. These data indicate that M. tuberculosis and its potent TLR2 ligands activate ERK signaling in macrophages to promote anti-inflammatory macrophage responses and blunt Th1 responses against the pathogen.     

Haemophilus ducreyi Infection Causes Basal Keratinocyte Cytotoxicity and Elicits a Unique Cytokine Induction Pattern in an In Vitro Human Skin Model

Haemophilus ducreyi is the etiologic agent of the sexually transmitted genital ulcer disease chancroid. Predominantly a cutaneous pathogen, H. ducreyi is present in chancroid ulcers that are characterized by extensive neutrophil accumulation in intraepidermal lesions accompanied by a mononuclear infiltrate in the dermis. We used an in vitro human skin model composed of foreskin fibroblasts and keratinocytes to examine host skin cell interactions with H. ducreyi 35000. Bacteria replicated and persisted in artificial skin for at least 14 days. We observed H. ducreyi inside suprabasal keratinocytes using transmission electron microscopy. Although no bacteria were seen in the basal keratinocyte region, these cells were disrupted in infected cocultures. H. ducreyi infection stimulated increased secretion of interleukin-6 (IL-6) and IL-8 by skin cells. Conversely, tumor necrosis factor alpha and IL-1α levels were not elevated. IL-8 produced in response to H. ducreyi infection may be involved in recruiting polymorphonuclear leukocytes and other inflammatory cells, thereby contributing to the tissue necrosis and ulcer formation characteristic of chancroid.     

Replication of Salmonella enterica Serovar Typhimurium in Human Monocyte-Derived Macrophages

Salmonella enterica serovar Typhimurium is a common cause of food-borne gastrointestinal illness, but additionally it causes potentially fatal bacteremia in some immunocompromised patients. In mice, systemic spread and replication of the bacteria depend upon infection of and replication within macrophages, but replication in human macrophages is not widely reported or well studied. In order to assess the ability of Salmonella Typhimurium to replicate in human macrophages, we infected primary monocyte-derived macrophages (MDM) that had been differentiated under conditions known to generate different phenotypes. We found that replication in MDM depends greatly upon the phenotype of the cells, as M1-skewed macrophages did not allow replication, while M2a macrophages and macrophages differentiated with macrophage colony-stimulating factor (M-CSF) alone (termed M0) did. We describe how additional conditions that alter the macrophage phenotype or the gene expression of the bacteria affect the outcome of infection. In M0 MDM, the temporal expression of representative genes from Salmonella pathogenicity islands 1 and 2 (SPI1 and SPI2) and the importance of the PhoP/Q two-component regulatory system are similar to what has been shown in mouse macrophages. However, in contrast to mouse macrophages, where replication is SPI2 dependent, we observed early SPI2-independent replication in addition to later SPI2-dependent replication in M0 macrophages. Only SPI2-dependent replication was associated with death of the host cell at later time points. Altogether, our results reveal a very nuanced interaction between Salmonella and human macrophages.     

Liposomes of phosphatidylcholine and cholesterol induce an M2-like macrophage phenotype reprogrammable to M1 pattern with the involvement of B-1 cells

Macrophages respond to endogenous and non-self stimuli acquiring the M1 or M2 phenotypes, corresponding to classical or alternative activation, respectively. The role of B-1 cells in the regulation of macrophage polarization through the secretion of interleukin (IL)-10 has been demonstrated. However, the influence of B-1 cells on macrophage phenotype induction by an immunogen that suppress their ability to secrete IL-10 has not been explored. Here, we studied the peritoneal macrophage pattern induced by liposomes comprised of dipalmitoylphosphatidylcholine (DPPC) and cholesterol (Chol) carrying ovalbumin (OVA) (Lp DPPC/OVA), and the involvement of B-1 cells in macrophage polarization. Peritoneal cells from BALB/c, B-1 cells-deficient BALB/xid and C57BL/6 mice immunized with Lp DPPC/OVA and OVA in soluble form (PBS/OVA) were analyzed and stimulated or not in vitro with lipopolysaccharide (LPS). Peritoneal macrophages from BALB/c and C57BL/6 mice immunized with Lp DPPC/OVA showed an M2-like phenotype as evidenced by their high arginase activity without LPS stimulation. Upon stimulation, these macrophages were reprogrammable toward the M1 phenotype with the upregulation of nitric oxide (NO) and a decrease in IL-10 secretion. In addition, high IFN-γ levels were detected in the culture supernatant of peritoneal cells from BALB/c and C57BL/6 mice immunized with Lp DPPC/OVA. Nevertheless, still high levels of arginase activity and undetectable levels of IL-12 were found, indicating that the switch to a classical activation state was not complete. In the peritoneal cells from liposomes-immunized BALB/xid mice, levels of arginase activity, NO, and IL-6 were below those from wild type animals, but the last two products were restored upon adoptive transfer of B-1 cells, together with an increase in IFN-γ secretion. Summarizing, we have demonstrated that Lp DPPC/OVA induce an M2-like pattern in peritoneal macrophages reprogrammable to M1 phenotype after LPS stimulation, with the involvement of B-1 cells.     

Short ragweed pollen promotes M2 macrophage polarization via TSLP/TSLPR/OX40L signaling in allergic inflammation

This study was to explore the role and mechanism of macrophages in pollen-triggered allergic inflammation. A murine model of short ragweed (SRW) pollen-induced experimental allergic conjunctivitis (EAC), and bone marrow (BM)-macrophages cultures were used. Typical allergic manifestations and TSLP-stimulated Th2 hyperresponse were observed in ocular surface of EAC model in wild-type (WT) mice induced by SRW. The M2 phenotype markers, Arg1, Ym1 and FIZZ1, were highly expressed by conjunctiva and draining cervical lymph nodes (CLNs) of WT-EAC mice when compared with controls, as evaluated by RT-qPCR and Immunofluorescent double staining with macrophage marker F4/80. The stimulated expression of TSLPR and OX40L by macrophage was detected in conjunctiva and CLNs by RT-qPCR, double staining, and flow cytometry. M2 macrophages were found to produce TARC and MDC. In contrast, EAC model with TSLPR^−/− mice did not show allergic signs and any increase of Th2 cytokines (IL-4, IL-5 and IL-13) and M2 markers. In vitro cultures confirmed that SRW extract stimulates expression of TSLPR, OX40L, TARC, MDC, and three M2 markers by BM-macrophages from WT mice, but not from TSLPR^−/− mice. These findings demonstrate that SRW pollen primes macrophage polarization toward to M2 phenotype via TSLP/TSLPR/OX40L signaling to amplify allergic inflammation.     

CD14 Influences Host Immune Responses and Alternative Activation of Macrophages during Schistosoma mansoni Infection

Antigen-presenting cell (APC) plasticity is critical for controlling inflammation in metabolic diseases and infections. The roles that pattern recognition receptors (PRRs) play in regulating APC phenotypes are just now being defined. We evaluated the expression of PRRs on APCs in mice infected with the helminth parasite Schistosoma mansoni and observed an upregulation of CD14 expression on macrophages. Schistosome-infected Cd14^−/− mice showed significantly increased alternative activation of (M2) macrophages in the livers compared to infected wild-type (wt) mice. In addition, splenocytes from infected Cd14^−/− mice exhibited increased production of CD4⁺-specific interleukin-4 (IL-4), IL-5, and IL-13 and CD4⁺Foxp3⁺IL-10⁺ regulatory T cells compared to cells from infected wt mice. S. mansoni-infected Cd14^−/− mice also presented with smaller liver egg granulomas associated with increased collagen deposition compared to granulomas in infected wt mice. The highest expression of CD14 was found on liver macrophages in infected mice. To determine if the Cd14^−/− phenotype was in part due to increased M2 macrophages, we adoptively transferred wt macrophages into Cd14^−/− mice and normalized the M2 and CD4⁺ Th cell balance close to that observed in infected wt mice. Finally, we demonstrated that CD14 regulates STAT6 activation, as Cd14^−/− mice had increased STAT6 activation in vivo, suggesting that lack of CD14 impacts the IL-4Rα-STAT6 pathway, altering macrophage polarization during parasite infection. Collectively, these data identify a previously unrecognized role for CD14 in regulating macrophage plasticity and CD4⁺ T cell biasing during helminth infection.     

The improvement of M1 polarization in macrophages by glycopeptide derived from <Emphasis Type="Italic">Ganoderma lucidum</Emphasis>

Ganoderma lucidum (Fr.) Karst (Ganodermataceae) is a medicinal mushroom that has been extensively used in China for centuries to promote longevity and improve vigor without significant adverse effects. There is continuous interest in the bioactive properties of G. lucidum in view of its newly developed popularity in other regions besides Asia, such as Europe. Glycopeptide derived from G. lucidum (Gl-PS) is one of the main effective components isolated from this mushroom. The Gl-PS has been demonstrated pleiotropic with many bioactivities including immunomodulatory and antitumor effects. Macrophages are important cells involved in innate and adaptive immunity. Classically activated macrophages (M1) and alternatively activated macrophages (M2), with their different roles, display distinct cytokine profiles: M1 preferentially produces TNF-α, IL-6, and IL-12; conversely, M2 generates more IL-10 and arginase. Gl-PS might have the potential to promote macrophage M1 polarization by lipopolysaccharide (LPS). In this study, LPS was used to induce the M1 polarization. It was shown that the level of the TNF-α, IL-6, and IL-12 were increased and the IL-10 and arginase I were decreased in the polarized M1 macrophages after application of Gl-PS compared to the control. The results indicated the potential of Gl-PS to promote M1 polarization vs M2, with the health beneficial understanding of the bioactivities of Gl-PS.     

Chlamydia trachomatis induces anti-inflammatory effect in human macrophages by attenuation of immune mediators in Jurkat T-cells

The chronic course of Chlamydia trachomatis infection is subtle with no obvious unusual inflammatory change. The reason for this is not clear. The data reported here explain how macrophage usual inflammatory response switches to anti-inflammatory response during C. trachomatis infection of mixed culture of macrophages and Jurkat T-cells. We assessed the establishment of productive infection in individual or mixed cell culture models, determined the status of C. trachomatis in the cells by monitoring HSP-60:MOMP or the proportions of the estimated IFUs that shed HSP-60 or MOMP. Also, the specific time-course expression of IL-12, IL-10 and IFN-γ or IL-12R, IL-10R, and IFN-γ-R during infection of cell models was assessed. Finally, the early events in cytokine elaboration in circumstances of varying intracellular Ca²⁺ levels were determined. There was evidence of productive infection in all individual and mixed cell culture models. The shedding of HSP-60 was highest in THP-1/Jurkat mixed cell culture model. The proportions of IFU that shed HSP-60 was heightened in infected THP-1/Jurkat mixed culture model, while the proportion of IFU that shed MOMP was higher in infected macrophage/Jurkat mixed culture and infected macrophages only. There was profound early elaboration of IL-10, varying significantly from IL-12 and IFN-γ in all infected individual or mixed cell culture models except in the case of Jurkat; where all cytokine elaboration was downregulated. The receptor to IL-10 was upregulated in infected macrophage/Jurkat cells and THP-1/Jurkat cells compared with other models in which IL-12 and IFN-γ receptors were more expressed. There was no observed significant change in cytokine in any model following the impairment of intracellular Ca²⁺ except in the case of macrophage/Jurkat cell model in which IL-12 and IL-10 were upregulated in 1 h or 3 h, respectively. The implication of these findings is that C. trachomatis mediates a switch from inflammatory to anti-inflammatory function in macrophages due to downregulation of the regulatory cytokine, IFN-γ in Jurkat cells, culminating in C. trachomatis chronic course.     

Transient depletion of CD4+ CD25+ regulatory T cells results in multiple autoimmune diseases in wild‐type and B‐cell‐deficient NOD mice

Plasticity is a hallmark of macrophages, and in response to environmental signals these cells undergo different forms of polarized activation, the extremes of which are called classic (M1) and alternative (M2). Rapamycin (RAPA) is crucial for survival and functions of myeloid phagocytes, but its effects on macrophage polarization are not yet studied. To address this issue, human macrophages obtained from six normal blood donors were polarized to M1 or M2 in vitro by lipopolysaccharide plus interferon-γ or interleukin-4 (IL-4), respectively. The presence of RAPA (10 ng/ml) induced macrophage apoptosis in M2 but not in M1. Beyond the impact on survival in M2, RAPA reduced CXCR4, CD206 and CD209 expression and stem cell growth factor-β, CCL18 and CCL13 release. In contrast, in M1 RAPA increased CD86 and CCR7 expression and IL-6, tumour necrosis factor-α and IL-1β release but reduced CD206 and CD209 expression and IL-10, vascular endothelial growth factor and CCL18 release. In view of the in vitro data, we examined the in vivo effect of RAPA monotherapy (0·1 mg/kg/day) in 12 patients who were treated for at least 1 month before islet transplant. Cytokine release by Toll-like receptor 4-stimulated peripheral blood mononuclear cells showed a clear shift to an M1-like profile. Moreover, macrophage polarization 21 days after treatment showed a significant quantitative shift to M1. These results suggest a role of mammalian target of rapamycin (mTOR) into the molecular mechanisms of macrophage polarization and propose new therapeutic strategies for human M2-related diseases through mTOR inhibitor treatment.     

Irf5 deficiency in myeloid cells prevents necrotizing enterocolitis by inhibiting M1 macrophage polarization

Necrotizing enterocolitis (NEC) is a life-threatening inflammatory disease in newborns, but the mechanisms remain unclear. Interferon regulatory factor 5 (IRF5) is a master regulator of macrophage function and is essential for proinflammatory M1 macrophage polarization. Our previous data indicated that M1 macrophages promote NEC injury. Here, we investigated whether IRF5 is involved in the pathogenesis of NEC. First, we found that IRF5 was upregulated in infiltrated macrophages in human neonates with NEC compared to controls. We further confirmed IRF5 upregulation in macrophages in experimental murine NEC and that the infiltrated macrophages were predominantly polarized into the M1 but not the M2 phenotype. Myeloid-specific deficiency of Irf5, which was associated with reduced M1 macrophage polarization and systematic inflammation, dramatically prevented experimental NEC. Moreover, we found that the ablation of Irf5 in myeloid cells markedly suppressed intestinal epithelial cell apoptosis and further prevented intestinal barrier dysfunction in experimental NEC. Bioinformatic and chromatin immunoprecipitation analysis further showed that IRF5 binds to the promoters of the M1 macrophage-associated genes Ccl4, Ccl5, Tnf, and Il12b. Overall, our study provides evidence that IRF5 participates in the pathogenesis of NEC, while the deletion of Irf5 in myeloid cells prevents NEC via inhibiting M1 macrophage polarization.     

Kinetics of chemokine secretion in human macrophages infected with various strains of Mycobacterium tuberculosis

Background and Purpose: It has been shown that chemokine secretion upon infection with Mycobacterium tuberculosis is influenced by the virulence of the strain, and it is suggested that virulence-associated differences in chemokine secretion contribute to the failure in containing the infection due to poor granuloma formation. Materials and Methods: In this study, we used prevalent M tuberculosis clinical strains (S7 and S10) to study the chemokine secretion profile in infected THP-1 cells and monocyte-derived macrophages (MDM) and compared this with the chemokine secretion induced by laboratory strains. Results: This study showed that comparatively lower levels of IP-10 were induced by clinical strains than by laboratory strains in both differentiated THP-1 and MDMs. The secretion of MIP-1α was also depressed but only in the THP-1 cells infected with clinical strains. This depressed chemokine secretion may hinder the movement of Th-1 cells from the periphery into the infection foci to control the infection. Correlation between IP-10 and IL-12p40 showed a negative relationship in control MDMs, while there was a positive correlation in all the infected strains, indicating their cooperative role in attracting and activating Th1 cells for a protective immune response at the site. This relationship was strain dependent, with avirulent H37Ra showing higher correlation, followed by the clinical strains and the virulent H37Rv. A positive correlation of IP-10 with IFN-γ (S7 and H37Ra) and with IL-10 (H37Ra and H37Rv) suggested a definitive interplay of these molecules in infection. Conclusions: The chemokines secretion by infected THP-1 cells and MDMs was strain dependant and the lower induction by the clinical strains may indicate that the clinical strains maintain a quiescent nature to mislead the host immune system for their benefit.     

Pneumocystis infection alters the activation state of pulmonary macrophages

Recent studies show a substantial incidence of Pneumocystis jirovecii colonization and infection in patients with chronic inflammatory lung conditions. However, little is known about the impact of Pneumocystis upon the regulation of pulmonary immunity. We demonstrate here that Pneumocystis polarizes macrophages towards an alternatively activated macrophage-like phenotype. Genetically engineered mice that lack the ability to signal through IL-4 and IL-13 were used to show that Pneumocystis alternative macrophage activation is dependent upon signaling through these cytokines. To determine whether Pneumocystis-induced macrophage polarization would impact subsequent immune responses, we infected mice with Pneumocystis and then challenged them with Pseudomonas aeruginosa 14 days later. In co-infected animals, a higher proportion of macrophages in the alveolar and interstitial spaces expressed both classical and alternatively activated markers and produced the regulatory cytokines TGFβ and IL-10, as well as higher arginase levels than in mice infected with P. aeruginosa alone. Our results suggest that Pneumocystis reprograms the overall macrophage repertoire in the lung to that of a more alternatively-activated setpoint, thereby altering subsequent immune responses. These data may help to explain the association between Pneumocystis infection and decline in pulmonary function.     

Dynamic Changes of Microglia/Macrophage M1 and M2 Polarization in Theiler's Murine Encephalomyelitis

Microglia and macrophages play a central role for demyelination in Theiler's murine encephalomyelitis (TME) virus infection, a commonly used infectious model for chronic‐progressive multiple sclerosis. In order to determine the dynamic changes of microglia/macrophage polarization in TME, the spinal cord of Swiss Jim Lambert (SJL) mice was investigated by gene expression profiling and immunofluorescence. Virus persistence and demyelinating leukomyelitis were confirmed by immunohistochemistry and histology. Electron microscopy revealed continuous myelin loss together with abortive myelin repair during the late chronic infection phase indicative of incomplete remyelination. A total of 59 genes out of 151 M1‐ and M2‐related genes were differentially expressed in TME virus‐infected mice over the study period. The onset of virus‐induced demyelination was associated with a dominating M1 polarization, while mounting M2 polarization of macrophages/microglia together with sustained prominent M1‐related gene expression was present during the chronic‐progressive phase. Molecular results were confirmed by immunofluorescence, showing an increased spinal cord accumulation of CD16/32⁺ M1‐, arginase‐1⁺ M2‐ and Ym1⁺ M2‐type cells associated with progressive demyelination. The present study provides a comprehensive database of M1‐/M2‐related gene expression involved in the initiation and progression of demyelination supporting the hypothesis that perpetuating interaction between virus and macrophages/microglia induces a vicious circle with persistent inflammation and impaired myelin repair in TME.     

Serum-Mediated Activation of Macrophages Reflects TcVac2 Vaccine Efficacy against Chagas Disease

Chagas disease is endemic in Latin America and an emerging infectious disease in the United States. No effective treatments are available. The TcG1, TcG2, and TcG4 antigens are highly conserved in clinically relevant Trypanosoma cruzi isolates and are recognized by B and T cells in infected hosts. Delivery of these antigens as a DNA prime/protein boost vaccine (TcVac2) elicited lytic antibodies and type 1 CD8⁺ T cells that expanded upon challenge infection and provided >90% control of parasite burden and myocarditis in chagasic mice. Here we determined if peripheral blood can be utilized to capture the TcVac2-induced protection from Chagas disease. We evaluated the serum levels of T. cruzi kinetoplast DNA (TckDNA), T. cruzi 18S ribosomal DNA (Tc18SrDNA), and murine mitochondrial DNA (mtDNA) as indicators of parasite persistence and tissue damage and monitored the effect of sera on macrophage phenotype. Circulating TckDNA/Tc18SrDNA and mtDNA were decreased by >3- to 5-fold and 2-fold, respectively, in vaccinated infected mice compared to nonvaccinated infected mice. Macrophages incubated with sera from vaccinated infected mice exhibited M2 surface markers (CD16, CD32, CD200, and CD206), moderate proliferation, a low oxidative/nitrosative burst, and a regulatory/anti-inflammatory cytokine response (interleukin-4 [IL-4] plus IL-10 > tumor necrosis factor alpha [TNF-α]). In comparison, macrophages incubated with sera from nonvaccinated infected mice exhibited M1 surface markers, vigorous proliferation, a substantial oxidative/nitrosative burst, and a proinflammatory cytokine response (TNF-α ≫ IL-4 plus IL-10). Cardiac infiltration of macrophages and TNF-α and oxidant levels were significantly reduced in TcVac2-immunized chagasic mice. We conclude that circulating TcDNA and mtDNA levels and macrophage phenotype mediated by serum constituents reflect in vivo levels of parasite persistence, tissue damage, and inflammatory/anti-inflammatory state and have potential utility in evaluating disease severity and efficacy of vaccines and drug therapies.     

Macrophage Polarization during Murine Lyme Borreliosis

Infection of C3H mice with Borrelia burgdorferi, the causative agent of Lyme disease, reliably produces an infectious arthritis and carditis that peak around 3 weeks postinfection and then spontaneously resolve. Macrophage polarization has been suggested to drive inflammation, the clearance of bacteria, and tissue repair and resolution in a variety of infectious disease models. During Lyme disease it is clear that macrophages are capable of clearing Borrelia spirochetes and exhausted neutrophils; however, the role of macrophage phenotype in disease development or resolution has not been studied. Using classical (NOS2) and alternative (CD206) macrophage subset-specific markers, we determined the phenotype of F4/80⁺ macrophages within the joints and heart throughout the infection time course. Within the joint, CD206⁺ macrophages dominated throughout the course of infection, and NOS2⁺ macrophage numbers became elevated only during the peak of inflammation. We also found dual NOS2⁺ CD206⁺ macrophages which increased during resolution. In contrast to findings for the ankle joints, numbers of NOS2⁺ and CD206⁺ macrophages in the heart were similar at the peak of inflammation. 5-Lipoxygenase-deficient (5-LOX^−/−) mice, which display a failure of Lyme arthritis resolution, recruited fewer F4/80⁺ cells to the infected joints and heart, but macrophage subset populations were unchanged. These results highlight differences in the inflammatory infiltrates during Lyme arthritis and carditis and demonstrate the coexistence of multiple macrophage subsets within a single inflammatory site.     

Macrophage Migration Inhibitory Factor contributes to drive phenotypic and functional macrophages activation in response to Toxoplasma gondii infection

Cytokines are small molecules secreted by numerous cells. Macrophage Migration Inhibitory Factor (MIF) is a cytokine initially described due to its function of inhibiting random macrophage migration. Currently, new functions have been described for MIF, such as stimulating inflammatory functions in response to infections by microorganisms including, Toxoplasma gondii. However, the primordial MIF function related to macrophages has been little addressed. The main purpose of the study was to recapitulate MIF function on macrophages in response to T. gondii infection. To achieve this goal, peritoneal macrophages were collected from C57BL/6WT and Mif1^-/- mice after recruitment with thioglycolate. Macrophages were cultured, treated with 4-Iodo-6-phenylpyrimidine (4-IPP), and infected or not by T. gondii for 24 h. Following this, the culture supernatant was collected for cytokine, urea and nitrite analysis. In addition, macrophages were evaluated for phagocytic activity and T. gondii proliferation rates. Results demonstrated that T. gondii infection triggered an increase in MIF production in the WT group as well as an increase in the secretion of IL-10, TNF, IFN-γ, IL-6 and IL-17 in the WT and Mif1^-/- macrophages. Regarding the comparison between groups, it was detected that Mif1^-/- macrophages secreted more IL-10 compared to WT. On the other hand, the WT macrophages produced greater amounts of TNF, IFN-γ, IL-6 and IL-17. Urea production was more pronounced in Mif1^-/- macrophages while nitrite production was higher in WT macrophages. T. gondii showed a greater ability to proliferate in Mif1^-/- macrophages and these cells also presented enhanced phagocytic activity. In conclusion, T. gondii infection induces macrophage activation inciting cytokine production. In presence of MIF, T. gondii infected macrophages produce pro-inflammatory cytokines compatible with the M1 activation profile. MIF absence caused a dramatic reduction in pro-inflammatory cytokines that are balanced by increased levels of urea and anti-inflammatory cytokines. These macrophages presented increased phagocytic capacity and shared features activation with the M2 profile.