Macrophage migration inhibitory factor plays a critical role in mediating protection against the helminth parasite Taenia crassiceps

Macrophage Migration Inhibitory Factor (MIF) is a Key Player in Dry Eye Disease

PURPOSE

To explore the role of the proinflammatory cytokine, macrophage migration inhibitory factor (MIF), in a murine model of dry eye disease (DED).

METHODS

The role of MIF on DED was determined using genetically MIF deficient mice and pharmacological inhibition of MIF. DED was induced with 0.5 mg of scopolamine via subcutaneous injection in wild type (WT) and mice lacking MIF (Mif-/-), three times a day for 21 days. DED signs, tear volume, ferning pattern and cytology impression were evaluated. Also, eye tissues were collected to determine transcripts of key inflammatory mediators and histopathological damage. In a second set of experiments, we neutralized MIF with ISO-1, an isozaxiline-derivative MIF tautomerase activity-inhibiting small molecule in WT mice, following an acute DED model for 10 days. ISO-1 was given starting on day 3 after DED induction and signs were evaluated, including a recovery phase in both experimental approaches.

RESULTS

When compared to WT, Mif-/- mice showed attenuated signs of DED like preserved mucin pattern and increased tear volume. Also, Mif-/- mice maintained conjunctival epithelial cells and less corneal damage, associated with lower levels of TNFα and IL-1β. At recovery phase, Mif-/- mice presented improved signs. Interestingly, in cornea and conjunctiva the absence of MIF selectively downregulated the transcription of inflammatory enzymes like inos and nox4 whereas displayed enhanced transcripts of il-4, il-13, tgfβ and cox2. Finally, pharmacological inhibition of MIF using ISO-1, replicated the above findings in the mouse model.

CONCLUSION

MIF is a central positive mediator of the inflammatory process in experimental DED, thus, targeting MIF could be used as a novel therapy in ocular surface inflammatory pathologies.

Differential Protein Expression of Taenia crassiceps ORF Strain in the Murine Cysticercosis Model Using Resistant (C57BL/6) Mice

A cysticercosis model of Taenia crassiceps ORF strain in susceptible BALB/c mice revealed a Th2 response after 4 weeks, allowing for the growth of the parasite, whereas resistant C57BL/6 mice developed a sustained Th1 response, limiting parasitic growth. However, little is known about how cysticerci respond to an immunological environment in resistant mice. Here, we show that the Th1 response, during infection in resistant C57BL/6 mice, lasted up to 8 weeks and kept parasitemia low. Proteomics analysis of parasites during this Th1 environment showed an average of 128 expressed proteins; we chose 15 proteins whose differential expression varied between 70 and 100%. A total of 11 proteins were identified that formed a group whose expression increased at 4 weeks and decreased at 8 weeks, and another group with proteins whose expression was high at 2 weeks and decreased at 8 weeks. These identified proteins participate in tissue repair, immunoregulation and parasite establishment. This suggests that T. crassiceps cysticerci in mice resistant under the Th1 environment express proteins that control damage and help to establish a parasite in the host. These proteins could be targets for drugs or vaccine development.

Macrophage migration inhibitory factor contributes to immunopathogenesis during Plasmodium yoelii 17XL infection

Macrophage migration inhibitory factor (MIF) is a cytokine recognized regulator of the inflammatory immune response associated with several immune cells that produce inflammatory cytokines such as IL-1β, IL-6, IL-12, IL-18, and TNF-α. This study aimed to understand the effect of MIF on the immune response and pathogenesis during Plasmodium infection. Wild-type (Wt) and MIF knockout (Mif ^-/-) mice were intravenously infected with 1×10³ Plasmodium yoelii (Py) 17XL-parasitized red blood cells. Our data showed that Py17XL-infected Wt mice died 11 days postinfection, while Mif ^-/- mice showed reduced parasitemia and an increase in their survival at day 11 up to 58%, importantly they succumb up to day 21 postinfection. The increased survival rate in Mif ^-/- mice was associated with less severe cachexia and anemia as a result of a mixed Th1/Th2 cytokine profile, high levels of IL-12, IL-17/IL-4, and IL-10 in serum; and high levels of IL-4 and IL-10, and low levels of IFN-γ in spleen cells compared to Py17XL infected Wt mice. Moreover, macrophages (Mφs) from Mif ^-/- mice exhibited higher concentrations of IL-10 and IL-12 and reduced levels of TNF-α and nitric oxide (NO) compared to Py17XL-infected Wt mice. These results demonstrate that MIF has an important role in regulating the immune response associated with host pathogenesis and lethality, which is relevant to consider in preventing/reducing complications in Plasmodium infections.

The IL-25-dependent tuft cell circuit driven by intestinal helminths requires macrophage migration inhibitory factor (MIF)

Macrophage migration inhibitory factor (MIF) is a key innate immune mediator with chemokine- and cytokine-like properties in the inflammatory pathway. While its actions on macrophages are well-studied, its effects on other cell types are less understood. Here we report that MIF is required for expansion of intestinal tuft cells during infection with the helminth Nippostrongylus brasiliensis. MIF-deficient mice show defective innate responses following infection, lacking intestinal epithelial tuft cell hyperplasia or upregulation of goblet cell RELMβ, and fail to expand eosinophil, type 2 innate lymphoid cell (ILC2) and macrophage (M2) populations. Similar effects were observed in MIF-sufficient wild-type mice given the MIF inhibitor 4-IPP. MIF had no direct effect on epithelial cells in organoid cultures, and MIF-deficient intestinal stem cells could generate tuft cells in vitro in the presence of type 2 cytokines. In vivo the lack of MIF could be fully compensated by administration of IL-25, restoring tuft cell differentiation and goblet cell expression of RELM-β, demonstrating its requirement upstream of the ILC2-tuft cell circuit. Both ILC2s and macrophages expressed the MIF receptor CXCR4, indicating that MIF may act as an essential co-factor on both cell types to activate responses to IL-25 in helminth infection.

Inhibition of Macrophage Migration Inhibitory Factor Activity Attenuates Haemorrhagic Shock-Induced Multiple Organ Dysfunction in Rats

Objective

The aim of this study was to investigate (a) macrophage migration inhibitory factor (MIF) levels in polytrauma patients and rats after haemorrhagic shock (HS), (b) the potential of the MIF inhibitor ISO-1 to reduce multiple organ dysfunction syndrome (MODS) in acute (short-term and long-term follow-up) HS rat models and (c) whether treatment with ISO-1 attenuates NF-κB and NLRP3 activation in HS.

Background

The MODS caused by an excessive systemic inflammatory response following trauma is associated with a high morbidity and mortality. MIF is a pleiotropic cytokine which can modulate the inflammatory response, however, its role in trauma is unknown.

Methods

The MIF levels in plasma of polytrauma patients and serum of rats with HS were measured by ELISA. Acute HS rat models were performed to determine the influence of ISO-1 on MODS. The activation of NF-κB and NLRP3 pathways were analysed by western blot in the kidney and liver.

Results

We demonstrated that (a) MIF levels are increased in polytrauma patients on arrival to the emergency room and in rats after HS, (b) HS caused organ injury and/or dysfunction and hypotension (post-resuscitation) in rats, while (c) treatment of HS-rats with ISO-1 attenuated the organ injury and dysfunction in acute HS models and (d) reduced the activation of NF-κB and NLRP3 pathways in the kidney and liver.

Conclusion

Our results point to a role of MIF in the pathophysiology of trauma-induced organ injury and dysfunction and indicate that MIF inhibitors may be used as a potential therapeutic approach for MODS after trauma and/or haemorrhage.

The Role of MIF on Eosinophil Biology and Eosinophilic Inflammation

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine that participates in innate and adaptive immune responses. MIF contributes to the resistance against infection agents, but also to the cellular and tissue damage in infectious, autoimmune, and allergic diseases. In the past years, several studies demonstrated a critical role for MIF in the pathogenesis of type-2-mediated inflammation, including allergy and helminth infection. Atopic patients have increased MIF amounts in affected tissues, mainly produced by immune cells such as macrophages, Th2 cells, and eosinophils. Increased MIF mRNA and protein are found in activated Th2 cells, while eosinophils stock pre-formed MIF protein and secrete high amounts of MIF upon stimulation. In mouse models of allergic asthma, the lack of MIF causes an almost complete abrogation of the cardinal signs of the disease including mucus secretion, eosinophilic inflammation, and airway hyper-responsiveness. Additionally, blocking the expression of MIF in animal models leads to significant reduction of pathological signs of eosinophilic inflammation such as rhinitis, atopic dermatitis, eosinophilic esophagitis and helminth infection. A number of studies indicate that MIF is important in the effector phase of type-2 immune responses, while its contribution to Th2 differentiation and IgE production is not consensual. MIF has been found to intervene in different aspects of eosinophil physiology including differentiation, survival, activation, and migration. CD4+ T cells and eosinophils express CD74 and CXCR4, receptors able to signal upon MIF binding. Blockage of these receptors with neutralizing antibodies or small molecule antagonists also succeeds in reducing the signals of inflammation in experimental allergic models. Together, these studies demonstrate an important contribution of MIF on eosinophil biology and in the pathogenesis of allergic diseases and helminth infection.

Immune modulation by the macrophage migration inhibitory factor (MIF) family: D-dopachrome tautomerase (DDT) is not (always) a backup system

Human macrophage migration inhibition factor (MIF) is a protein with cytokine and chemokine properties that regulates a diverse range of physiological functions related to innate immunity and inflammation. Most research has focused on the role of MIF in different inflammatory diseases. D-dopachrome tautomerase (DDT), a different molecule with structural similarities to MIF, which shares receptors and biological functions, has recently been reported, but little is known about its roles and mechanisms. In this review, we sought to understand the similarities and differences between these molecules by summarizing what is known about their different structures, receptors and mechanisms regulating their expression and biological activities with an emphasis on immunological aspects.

Macrophage Activation and Functions during Helminth Infection: Recent Advances from the Laboratory Mouse

Macrophages are highly plastic innate immune cells that adopt an important diversity of phenotypes in response to environmental cues. Helminth infections induce strong type 2 cell-mediated immune responses, characterized among other things by production of high levels of interleukin- (IL-) 4 and IL-13. Alternative activation of macrophages by IL-4 in vitro was described as an opposite phenotype of classically activated macrophages, but the in vivo reality is much more complex. Their exact activation state as well as the role of these cells and associated molecules in type 2 immune responses remains to be fully understood. We can take advantage of a variety of helminth models available, each of which have their own feature including life cycle, site of infection, or pathological mechanisms influencing macrophage biology. Here, we reviewed the recent advances from the laboratory mouse about macrophage origin, polarization, activation, and effector functions during parasitic helminth infection.

EXPERIMENTAL SUBCUTANEOUS CYSTICERCOSIS BY Taenia crassiceps IN BALB/c AND C57BL/6 MICE

Human cysticercosis is one of the most severe parasitic infections affecting tissues. Experimental models are needed to understand the host-parasite dynamics involved throughout the course of the infection. The subcutaneous experimental model is the closest to what is observed in human cysticercosis that does not affect the central nervous system. The aim of this study was to evaluate macroscopically and microscopically the experimental subcutaneous cysticercosis caused by Taenia crassiceps cysticerci in BALB/c and C57BL/6 mice. Animals were inoculated in the dorsal subcutaneous region and macroscopic and microscopic aspects of the inflammatory process in the host-parasite interface were evaluated until 90 days after the inoculation (DAI). All the infected animals presented vesicles containing cysticerci in the inoculation site, which was translucent at 7 DAI and then remained opaque throughout the experimental days. The microscopic analysis showed granulation tissue in BALB/c mice since the acute phase of infection evolving to chronicity without cure, presenting 80% of larval stage cysticerci at 90 DAI. While C57BL/6 mice presented 67% of final stage cysticerci at 90 DAI, the parasites were surrounded by neutrophils evolving to the infection control. It is possible to conclude that the genetic features of susceptibility (BALB/c) or resistance (C57BL/6) were confirmed in an experimental subcutaneous model of cysticercosis.

Macrophage migration inhibitory factor deficiency enhances immune response to Nippostrongylus brasiliensis

Infections with helminth parasites are endemic in the developing world and are a target for intervention with new therapies. Macrophage migration inhibitory factor (MIF) is a cytokine with pleiotropic effects in inflammation and immune responses. We investigated the role of MIF in a naturally cleared model of helminth infection in rodents, Nippostrongylus brasiliensis. At day 7 postinfection, MIF-deficient (MIF^-/-) mice had reduced parasite burden and mounted an enhanced type 2 immune response (Th2), including increased Gata3 expression and interleukin-13 (IL-13) production in the mesenteric lymph nodes (MLNs). Bone marrow reconstitution demonstrated that MIF produced from hematopoietic cells was crucial and Rag1^-/- reconstitution provided direct evidence that MIF^-/- CD4⁺ T cells were responsible for the augmented parasite clearance. MIF^-/- CD4⁺ T cells produced less IL-6 postinfection, which correlated with enhanced Th2 responses. MIF^-/- CD4⁺ T cells exhibited lower nuclear factor-κB activation, potentially explaining the reduction in IL-6. Finally, we demonstrated enhanced clearance of the parasite and Th2 response in wild-type mice treated with the MIF tautomerase inhibitor, sulforaphane, a compound found naturally found in cruciferous vegetables. These results are the first to describe the importance of the tautomerase enzyme activity in MIF function in N. brasiliensis infection.

Association of Macrophage Migration Inhibitory Factor Polymorphisms with Total Plasma IgE Levels in Patients with Atopic Dermatitis in Korea

The macrophage migration inhibitory factor (MIF) gene is located on human chromosome 22q11.2 and is linked to atopic phenotypes. Plasma MIF and log [total IgE] levels are significantly elevated in atopic dermatitis (AD) patients. The aim of this study was to evaluate the relationship between two MIF polymorphisms, −173 G to C and −794 CATT_5–8, and total plasma IgE levels in AD patients in Korea. We performed PCR-RFLP analysis in 178 AD patients and 80 control subjects to determine whether MIF SNPs are associated with susceptibility to AD. Plasma total IgE and MIF levels were determined, and then logistic regression analyses were performed to determine the associations between a SNP or haplotype and plasma total IgE or MIF levels. The −173 G/C polymorphism, located in the MIF promoter, was significantly associated with AD; the odds ratios (ORs) for the CC homozygotes and GC heterozygotes were 9.3 and 2.5, respectively. The MIF C/5-CATT and the MIF C/7-CATT haplotypes were significantly associated with AD; the ORs for the MIF C/5-CATT and MIF C/7-CATT haplotypes were 9.7 and 4.5, respectively. Log [total IgE] levels were highly associated with the MIF −794 7-CATT polymorphism. Notably, the MIF C/7-CATT haplotype was associated with a decrease in plasma log [total IgE] levels in a gene dose-dependent manner. Although log [MIF] levels were not associated with the MIF polymorphisms, the frequencies of the MIF C/5-CATT haplotype-containing genotypes decreased in order of MIF levels. Our results demonstrate that MIF promoter polymorphisms in the −173 C allele and the MIF C/5-CATT and C/7-CATT haplotypes were significantly associated with an increased risk for AD. In particular, the −794 7-CATT locus and the MIF C/7-CATT haplotype were significantly associated with decreased total IgE levels in the plasma, suggesting that these polymorphisms might be a marker for intrinsic AD rather than extrinsic AD that shows high total IgE levels and presence of allergen-specific IgE.

Macrophage migration inhibitory factor promotes eosinophil accumulation and tissue remodeling in eosinophilic esophagitis

Macrophage migration inhibitory factor (MIF) is involved in eosinophil biology and in type 2 inflammation, contributing to allergic and helminthic diseases. We hypothesized that MIF participates in the pathogenesis of eosinophilic esophagitis (EoE), an allergic condition characterized by esophageal eosinophilic inflammation. MIF is highly expressed in esophageal mucosa of patients with EoE, compared with gastro-esophageal reflux disease and control patients, where it co-localizes predominantly with eosinophils. In vitro, recombinant MIF promotes human eosinophil chemotaxis, while MIF antagonist and CXCR4 antagonist, AMD3100, revert this effect. In a model of EoE induced by ovalbumin, Mif-deficient mice have reduced inflammation and collagen deposition compared with wild-type (WT) mice. Importantly, treatment of WT mice with anti-MIF or with AMD3100 during the challenge phase prevents accumulation of eosinophils and tissue remodeling. Conversely, recombinant MIF promoted tissue eosinophil inflammation in allergic mice. Together, these results implicate MIF in the pathogenesis of esophageal inflammation and suggest that targeting MIF might represent a novel therapy for EoE.

E-cadherin expression in macrophages dampens their inflammatory responsiveness in vitro, but does not modulate M2-regulated pathologies in vivo

IL-4/IL-13-induced alternatively activated macrophages (M(IL-4/IL-13), AAMs or M2) are known to express E-cadherin, enabling them to engage in heterotypic cellular interactions and IL-4-driven macrophage fusion in vitro. Here we show that E-cadherin overexpression in Raw 264.7 macrophages inhibits their inflammatory response to LPS stimulation, as demonstrated by a reduced secretion of inflammatory mediators like interleukin (IL)-6, tumor necrosis factor (TNF) and nitric oxide (NO). To study the function of E-cadherin in M(IL-4/IL-13) macrophages in vivo, we generated macrophage-specific E-cadherin-deficient C57BL/6 mice. Using this new tool, we analyzed immunological parameters during two typical AAM-associated Th2-driven diseases and assessed Th2-associated granuloma formation. Although E-cadherin is strongly induced in AAMs during Taenia crassiceps helminth infections and allergic airway inflammation, its deletion in macrophages does not affect the course of both Th2 cytokine-driven diseases. Moreover, macrophage E-cadherin expression is largely redundant for granuloma formation around Schistosoma mansoni ova. Overall, we conclude that E-cadherin is a valuable AAM marker which suppresses the inflammatory response when overexpressed. Yet E-cadherin deletion in macrophages does not affect M(LPS+IFNγ) and M(IL-4) polarization in vitro, nor in vivo macrophage function, at least in the conditions tested.

Epigenetic pathways in macrophages emerge as novel targets in atherosclerosis

Atherosclerosis is a lipid-driven chronic inflammatory disorder. Monocytes and macrophages are key immune cells in the development of disease and clinical outcome. It is becoming increasingly clear that epigenetic pathways govern many aspects of monocyte and macrophage differentiation and activation. The dynamic regulation of epigenetic patterns provides opportunities to alter disease-associated epigenetic states. Therefore, pharmaceutical companies have embraced the targeting of epigenetic processes as new approaches for interventions. Particularly histone deacetylase (Hdac) inhibitors and DNA-methyltransferase inhibitors have long received attention and several of them have been approved for clinical use in relation to hematological malignancies. The key focus is still on oncology, but Alzheimer's disease, Huntington's disease and inflammatory disorders are coming in focus as well. These developments raise opportunities for the epigenetic targeting in cardiovascular disease (CVD). In this review we discuss the epigenetic regulation of the inflammatory pathways in relation to atherosclerosis with a specific attention to monocyte- and macrophage-related processes. What are the opportunities for future therapy of atherosclerosis by epigenetic interventions?

Pilot study: elevated circulating levels of the proinflammatory cytokine macrophage migration inhibitory factor in patients with chronic spinal cord injury

OBJECTIVE

To test the hypothesis that the proinflammatory cytokine macrophage migration inhibitory factor (MIF) is elevated in the circulation of patients with chronic spinal cord injury (SCI) relative to uninjured subjects, and secondarily to identify additional immune mediators that are elevated in subjects with chronic SCI.

DESIGN

Prospective, observational pilot study.

SETTING

Outpatient clinic of a department of physical medicine and rehabilitation and research institute in an academic medical center.

PARTICIPANTS

Individuals with chronic (>1y from initial injury) SCI (n=22) and age- and sex-matched uninjured subjects (n=19).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Plasma levels of MIF, as determined by a commercially available multiplex suspension immunoassay. The relationship between MIF levels and clinical/demographic variables was also examined. As a secondary outcome, we evaluated other cytokines, chemokines, and growth factors.

RESULTS

Plasma MIF levels were significantly higher in subjects with chronic SCI than in control subjects (P<.001). Elevated MIF levels were not correlated significantly with any one clinical or demographic characteristic. Subjects with SCI also exhibited significantly higher plasma levels of monokine induced by interferon-gamma/chemokine C-X-C motif ligand 9 (P<.03), macrophage colony stimulating factor (P<.035), interleukin-3 (P<.044), and stem cell growth factor beta (SCGF-β) (P<.016). Among subjects with SCI, the levels of SCGF-β increased with the time from initial injury.

CONCLUSIONS

These data confirm the hypothesis that MIF is elevated in subjects with chronic SCI and identify additional novel immune mediators that are also elevated in these subjects. This study suggests the importance of examining the potential functional roles of MIF and other immune factors in subjects with chronic SCI.

Development of the S3Pvac vaccine against murine Taenia crassiceps cysticercosis: a historical review

Our work of the last 25 yr was concerned with the development of a vaccine aimed to prevent porcine Taenia solium cysticercosis and was based on cross-reacting Taenia crassiceps antigens that had proved protective against experimental intraperitoneal murine T. crassiceps cysticercosis (EIMTcC). In recent times the efficacy of the vaccine has been considered in need of confirmation, and the use of EIMTcC has been questioned as a valid tool in screening for vaccine candidates among the many antigens possibly involved. A review of our work divided in 2 parts is presented at this point, the first dealing with EIMTcC and the second with porcine T. solium cysticercosis (presented in this issue). Herein, we revise our results using EIMTcC as a measure of the protective capacity of T. crassiceps complex antigen mixtures, of purified native antigens, and of S3Pvac anti-cysticercosis vaccine composed by 3 protective peptides: GK-1, KETc1, and KETc12 either synthetic or recombinantly expressed and collectively or separately, by diverse delivery systems when administered at different doses and by different routes. Statistical analyses of the data lead confidently to the strong inference that S3Pvac is indeed an effective vaccine against EIMTcC via specific and non-specific mechanisms of protection.

Macrophage migration inhibitory factor deficiency is associated with impaired killing of gram-negative bacteria by macrophages and increased susceptibility to Klebsiella pneumoniae sepsis

The cytokine macrophage migration inhibitory factor (MIF) is an important component of the early proinflammatory response of the innate immune system. However, the antimicrobial defense mechanisms mediated by MIF remain fairly mysterious. In the present study, we examined whether MIF controls bacterial uptake and clearance by professional phagocytes, using wild-type and MIF-deficient macrophages. MIF deficiency did not affect bacterial phagocytosis, but it strongly impaired the killing of gram-negative bacteria by macrophages and host defenses against gram-negative bacterial infection, as shown by increased mortality in a Klebsiella pneumonia model. Consistent with MIF's regulatory role of Toll-like 4 expression in macrophages, MIF-deficient cells stimulated with lipopolysaccharide or Escherichia coli exhibited reduced nuclear factor κB activity and tumor necrosis factor (TNF) production. Addition of recombinant MIF or TNF corrected the killing defect of MIF-deficient macrophages. Together, these data show that MIF is a key mediator of host responses against gram-negative bacteria, acting in part via a modulation of bacterial killing by macrophages.

Novel anti-inflammatory activity of epoxyazadiradione against macrophage migration inhibitory factor: inhibition of tautomerase and proinflammatory activities of macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is responsible for proinflammatory reactions in various infectious and non-infectious diseases. We have investigated the mechanism of anti-inflammatory activity of epoxyazadiradione, a limonoid purified from neem (Azadirachta indica) fruits, against MIF. Epoxyazadiradione inhibited the tautomerase activity of MIF of both human (huMIF) and malaria parasites (Plasmodium falciparum (PfMIF) and Plasmodium yoelii (PyMIF)) non-competitively in a reversible fashion (K(i), 2.11-5.23 μm). Epoxyazadiradione also significantly inhibited MIF (huMIF, PyMIF, and PfMIF)-mediated proinflammatory activities in RAW 264.7 cells. It prevented MIF-induced macrophage chemotactic migration, NF-κB translocation to the nucleus, up-regulation of inducible nitric-oxide synthase, and nitric oxide production in RAW 264.7 cells. Epoxyazadiradione not only exhibited anti-inflammatory activity in vitro but also in vivo. We tested the anti-inflammatory activity of epoxyazadiradione in vivo after co-administering LPS and MIF in mice to mimic the disease state of sepsis or bacterial infection. Epoxyazadiradione prevented the release of proinflammatory cytokines such as IL-1α, IL-1β, IL-6, and TNF-α when LPS and PyMIF were co-administered to BALB/c mice. The molecular basis of interaction of epoxyazadiradione with MIFs was explored with the help of computational chemistry tools and a biological knowledgebase. Docking simulation indicated that the binding was highly specific and allosteric in nature. The well known MIF inhibitor (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) inhibited huMIF but not MIF of parasitic origin. In contrast, epoxyazadiradione inhibited both huMIF and plasmodial MIF, thus bearing an immense therapeutic potential against proinflammatory reactions induced by MIF of both malaria parasites and human.

TLR2 mediates immunity to experimental cysticercosis

Information concerning TLR-mediated antigen recognition and regulation of immune responses during helminth infections is scarce. TLR2 is a key molecule required for innate immunity and is involved in the recognition of a wide range of viruses, bacteria, fungi and parasites. Here, we evaluated the role of TLR2 in a Taenia crassiceps cysticercosis model. We compared the course of T. crassiceps infection in C57BL/6 TLR2 knockout mice (TLR2^-/-) with that in wild type C57BL/6 (TLR2^+/+) mice. In addition, we assessed serum antibody and cytokine profiles, splenic cellular responses and cytokine profiles and the recruitment of alternatively activated macrophages (AAMφs) to the site of the infection. Unlike wild type mice, TLR2^-/- mice failed to produce significant levels of inflammatory cytokines in either the serum or the spleen during the first two weeks of Taenia infection. TLR2^-/- mice developed a Th2-dominant immune response, whereas TLR2^+/+ mice developed a Th1-dominant immune response after Taenia infection. The insufficient production of inflammatory cytokines at early time points and the lack of Th1-dominant adaptive immunity in TLR2^-/- mice were associated with significantly elevated parasite burdens; in contrast, TLR2^+/+ mice were resistant to infection. Furthermore, increased recruitment of AAMφs expressing PD-L1, PD-L2, OX40L and mannose receptor was observed in TLR2^-/- mice. Collectively, these findings indicate that TLR2-dependent signaling pathways are involved in the recognition of T. crassiceps and in the subsequent activation of the innate immune system and production of inflammatory cytokines, which appear to be essential to limit infection during experimental cysticercosis.

Effect of macrophage migration inhibitory factor (MIF) in human placental explants infected with Toxoplasma gondii depends on gestational age

Because macrophage migration inhibitory factor (MIF) is a key cytokine in pregnancy and has a role in inflammatory response and pathogen defense, the objective of the present study was to investigate the effects of MIF in first- and third-trimester human placental explants infected with Toxoplasma gondii. Explants were treated with recombinant MIF, IL-12, interferon-γ, transforming growth factor-β1, or IL-10, followed by infection with T. gondii RH strain tachyzoites. Supernatants of cultured explants were assessed for MIF production. Explants were processed for morphologic analysis, immunohistochemistry, and real-time PCR analysis. Comparison of infected and stimulated explants versus noninfected control explants demonstrated a significant increase in MIF release in first-trimester but not third-trimester explants. Tissue parasitism was higher in third- than in first-trimester explants. Moreover, T. gondii DNA content was lower in first-trimester explants treated with MIF compared with untreated explants. However, in third-trimester explants, MIF stimulus decreased T. gondii DNA content only at the highest concentration of the cytokine. In addition, high expression of MIF receptor was observed in first-trimester placental explants, whereas MIF receptor expression was low in third-trimester explants. In conclusion, MIF was up-regulated and demonstrated to be important for control of T. gondii infection in first-trimester explants, whereas lack of MIF up-regulation in third-trimester placentas may be involved in higher susceptibility to infection at this gestational age.

Macrophage migration inhibitory factor: a downregulator of early T cell-dependent IFN-gamma responses in Plasmodium chabaudi adami (556 KA)-infected mice

Neutralization of macrophage migration inhibitory factor (MIF) increases anti-tumor cytotoxic T cell responses in vivo and IFN-γ responses in vitro, suggesting a plausible regulatory role for MIF in T cell activation. Considering that IFN-γ production by CD4(+) T cells is pivotal to resolve murine malaria and that secretion of MIF is induced by Plasmodium chabaudi adami parasites, we investigated the effect of MIF deficiency on the infection with this pathogen. Infections with P. c. adami 556 KA parasites were more efficiently controlled in MIF-neutralized and MIF-deficient (knockout [KO]) BALB/c mice. The reduction in parasitemia was associated with reduced production of IL-4 by non-T/non-B cells throughout patent infection. At day 4 postinfection, higher numbers of activated CD4(+) cells were measured in MIF KO mice, which secreted more IFN-γ, less IL-4, and less IL-10 than did CD4(+) T cells from wild-type mice. Enhanced IFN-γ and decreased IL-4 responses also were measured in MIF KO CD4(+) T cells stimulated with or without IL-12 and anti-IL-4 blocking Ab to induce Th1 polarization. However, MIF KO CD4(+) T cells efficiently acquired a Th2 phenotype when stimulated in the presence of IL-4 and anti-IL-12 Ab, indicating normal responsiveness to IL-4/STAT6 signaling. These results suggest that by promoting IL-4 responses in cells other than T/B cells during early P. c. adami infection, MIF decreases IFN-γ secretion in CD4(+) T cells and, additionally, has the intrinsic ability to render CD4(+) T cells less capable of acquiring a robust Th1 phenotype when stimulated in the presence of IL-12.

A role for macrophage migration inhibitory factor in protective immunity against Aspergillus fumigatus

Inflammation plays an important role in protective immunity against fungi, including the opportunistic pathogen, Aspergillus fumigatus. The balance between pro-inflammatory and anti-inflammatory cytokines is a key determinant of infection outcome. Since macrophage migration inhibitory factor (MIF) is an upstream regulator of many cytokines, we analyzed herein the role of endogenous MIF in the host control of hematogenously disseminated aspergillosis using MIF⁻/⁻ mice. As revealed by their mortality rate, MIF⁻/⁻ mice were more susceptible to disseminated infection than WT mice. Moreover, pharmacologic inhibition of MIF with (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester, (ISO-1) increased the susceptibility of WT mice to lethal infection. The higher tissue fungal burden early in sublethal infection indicated increased susceptibility of MIF⁻/⁻ mice to sublethal infection as well. Substantial down-regulation of innate and acquired antifungal responses, characterized by decreased production of IL-1β, IL-6, TNF-α, IFN-γ and IL-17 in the spleen was noted in sublethally infected MIF⁻/⁻ mice. In contrast, IL-4 was higher in MIF⁻/⁻ than in WT mice. Taken together, our findings show that MIF contributes to host resistance against progressive invasive A. fumigatus infection by controlling downstream pro-inflammatory versus anti-inflammatory cytokine production thus determining the outcome of infection.

A small-molecule inhibitor of macrophage migration inhibitory factor for the treatment of inflammatory disease

Multiple sclerosis (MS) is a chronic, debilitating disease of the central nervous system (CNS) characterized by demyelination and axon loss. The proinflammatory cytokine macrophage migration inhibitory factor (MIF) has been shown to be elevated in the cerebrospinal fluid of patients during relapses. The purpose of this study was to evaluate a new small-molecule inhibitor of MIF and its ability to reduce the severity of an animal model of MS, experimental autoimmune encephalomyelitis (EAE). We utilized 2 structurally related isoxazolines, which show in vitro inhibition of MIF tautomerase activity. We found that administration of an inhibitor of MIF to mice with established EAE immediately reduced the severity of clinical signs and expanded a population of regulatory T lymphocytes. We also noted that the inhibitor reduced relapses of disease in a relapsing/remitting model of EAE. An analysis of leukocyte migration into the brain revealed that administration of inhibitor reduced entry of these cells. No effects on inflammatory cytokine production or T-cell activation in the periphery were noted. From these studies, we conclude that a small-molecule inhibitor of MIF reduces the severity of EAE and prevents access of immune cells into the CNS, which could be of therapeutic relevance to MS.

Cross-talk between macrophage migration inhibitory factor and eotaxin in allergic eosinophil activation forms leukotriene C₄-synthesizing lipid bodies

Recent studies have demonstrated an essential and nonredundant role for macrophage migration inhibitory factor (MIF) in asthma pathogenesis. Here we investigate the mechanisms involved in MIF-induced eosinophil activation. By using a model of allergic pulmonary inflammation, we observed that allergen challenge-elicited eosinophil influx, lipid body (also known as lipid droplets) biogenesis, and leukotriene (LT) C₄ synthesis are markedly reduced in Mif(-/-) compared with wild-type mice. Likewise, in vivo administration of MIF induced formation of new lipid bodies within eosinophils recruited to the inflammatory reaction site that corresponded to the intracellular compartment of increased LTC₄ synthesis. MIF-mediated eosinophil activation was at least in part due to a direct effect on eosinophils, because MIF was able to elicit lipid body assembly within human eosinophils in vitro, a phenomenon that was blocked by neutralization of the MIF receptor, CD74. MIF-induced eosinophil lipid body biogenesis, both in vivo and in vitro, was dependent on the cooperation of MIF and eotaxin acting in a positive-feedback loop, because anti-eotaxin and anti-CCR3 antibodies inhibit MIF-elicited lipid body formation, whereas eotaxin-induced lipid body formation is affected by anti-CD74 and MIF expression deficiency. Therefore, allergy-elicited inflammatory MIF acts in concert with eotaxin as a key activator of eosinophils to form LTC₄-synthesizing lipid bodies via cross-talk between CD74 and CCR3. Due to the effect of MIF on eosinophils, strategies that inhibit MIF activity might be of therapeutic value in controlling allergic inflammation.

Toxoplasma gondii: impaired maturation and pro-inflammatory response of dendritic cells in MIF-deficient mice favors susceptibility to infection

Macrophage migration inhibitory factor (MIF) has been found to be involved in host resistance to several parasitic infections. To determine the mechanisms of MIF-dependent responses to Toxoplasma gondii, we investigated host resistance in MIF-/- mice (BALB/c background) during natural oral infection. We focused on the potential involvement of MIF in Dendritic Cell (DC) maturation and IL-12 production. Following oral T. gondii infection, wild type mice developed a strong IL-12 response with an adequate maturation of their draining mesenteric lymph node DC (MLNDC) population and were resistant to challenge with either 40 or 100 cysts (ME49 strain). In contrast, similarly infected MIF-/- mice mounted a weak IL-12 response, displayed immature MLNDCs in the early phases of infection and rapidly succumbed to both type of challenges. Lack of maturation and IL-12 production of DCs in response to T. gondii antigens was confirmed by in vitro studies, and these effects were reversed following treatment with recombinant MIF. These findings demonstrate that MIF-induced early DC maturation and IL-12 production mediate resistance to T. gondii infection.

The unexpected role for the aryl hydrocarbon receptor on susceptibility to experimental toxoplasmosis

The aryl hydrocarbon receptor (AhR) is part of a signaling system that is mainly triggered by xenobiotic agents. Increasing evidence suggests that AhR may regulate immunity to infections. To determine the role of AhR in the outcome of toxoplasmosis, we used AhR−/− and wild-type (WT) mice. Following an intraperitoneal infection with Toxoplasma gondii (T. gondii), AhR−/− mice succumbed significantly faster than WT mice and displayed greater liver damage as well as higher serum levels of tumor necrosis factor (TNF)-α, nitric oxide (NO), and IgE but lower IL-10 secretion. Interestingly, lower numbers of cysts were found in their brains. Increased mortality was associated with reduced expression of GATA-3, IL-10, and 5-LOX mRNA in spleen cells but higher expression of IFN-γ mRNA. Additionally, peritoneal exudate cells from AhR−/− mice produced higher levels of IL-12 and IFN-γ but lower TLR2 expression than WT mice. These findings suggest a role for AhR in limiting the inflammatory response during toxoplasmosis.

Early removal of alternatively activated macrophages leads to Taenia crassiceps cysticercosis clearance in vivo

To determine the role of alternatively activated macrophages in modulating the outcome of experimental cysticercosis caused by Taenia crassiceps, we investigated the effect of removal of alternatively activated macrophage by injecting clodronate-loaded liposomes into susceptible BALB/c mice. Following T. crassiceps infection, mice receiving PBS-loaded liposomes developed a dominant Th2-type response associated with the presence of alternatively activated macrophages together with antigen-specific hyporesponsiveness and high parasite burden. In contrast, similarly infected mice treated with clodronate-loaded liposomes mounted a mixed Th1/Th2-type response, reversed antigen-specific hyporesponsiveness and did not carry notable alternatively activated macrophage populations. These factors were associated with increased resistance to T. crassiceps cysticercosis. Interestingly, early AAM phi depletion was enough to limit parasite growth. However, if macrophages were depleted late in the infection, no effect on parasite burden was observed. These findings demonstrate that alternatively activated macrophages play a critical role in mediating susceptibility to experimental cysticercosis in which their early recruitment may favor parasite survival.

Structural and functional comparison of MIF ortholog from Plasmodium yoelii with MIF from its rodent host

Host-derived macrophage migration inhibitory factor (MIF) has been implicated in the pathogenesis of malaria infection, especially in malarial anemia. Although two Plasmodium parasite-derived MIF orthologs, Plasmodium falciparum MIF and P. berghei MIF were identified recently, the crystal structure and the precise roles of Plasmodium-derived MIFs, particularly in combination with the host MIF, remain unknown. In this study, we identified another MIF ortholog from a rodent-specific P. yoelii (PyMIF). This molecule shares a conserved three-dimensional structure with murine MIF (MmMIF), but with a different substrate binding pattern and much lower tautomerase activity. It could activate host cells via several signaling pathways in vitro, and inhibiting macrophage apoptosis, also similarly to MmMIF. However, we found that PyMIF and MmMIF acted synergistically to activate the MAPK-ERK1/2 signaling pathway at very low concentration but acted antagonistically at higher concentration. Furthermore, we detected PyMIF in the sera of infected mice and found that injection of recombinant PyMIF (rPyMIF) during infection could up-regulate several pro-inflammatory cytokines in vivo and slightly delay the death of infected mice. These data suggest that PyMIF modulates host immune responses together with host MIF and has potential to prolong parasitemia or the chronicity of malaria infection.

Taenia crassiceps cysticercosis: variations in its parasite growth permissiveness that encounter with local immune features in BALB/c substrains

This study describes the first days of Taenia crassiceps infection in BALB/c substrains, BALB/cAnN and BALB/cJ, using two stocks of the same strains which were kept in different animal facilities, conventional and pathogen-free conditions, respectively. This study shows that parasite growth restriction shown by conventional BALB/cJ mice changed to parasite growth permissiveness when pathogen-free BALB/cJ mice were used. In addition, the higher number of macrophages, NK cells and intraperitoneal level of IFN-gamma found in the conventional restrictive BALB/cJ substrain vanished when the permissiveness to the parasite growth increased. No differences were found in DNA sequences of parasites collected before and after the change in the permissiveness to parasite growth which favors the possibility that the observed modifications could be due to changes in the murine strains and/or their maintenance conditions.

Alternative activation of macrophages: an immunologic functional perspective

Macrophages are innate immune cells with well-established roles in the primary response to pathogens, but also in tissue homeostasis, coordination of the adaptive immune response, inflammation, resolution, and repair. These cells recognize danger signals through receptors capable of inducing specialized activation programs. The classically known macrophage activation is induced by IFN-gamma, which triggers a harsh proinflammatory response that is required to kill intracellular pathogens. Macrophages also undergo alternative activation by IL-4 and IL-13, which trigger a different phenotype that is important for the immune response to parasites. Here we review the cellular sources of these cytokines, receptor signaling pathways, and induced markers and gene signatures. We draw attention to discrepancies found between mouse and human models of alternative activation. The evidence for in vivo alternative activation of macrophages is also analyzed, with nematode infection as prototypic disease. Finally, we revisit the concept of macrophage activation in the context of the immune response.

Analysis of macrophage migration inhibitory factor (MIF) in patients with idiopathic pulmonary fibrosis

By proteomic approach we previously characterised bronchoalveolar lavage (BAL) protein profiles of patients with idiopathic pulmonary fibrosis (IPF), sarcoidosis and systemic sclerosis. Among differently expressed proteins we identified macrophage migration inhibitory factor (MIF), a multi-function pleiotropic cytokine. This study was performed to validate our findings by a further proteomic approach and ELISA in a larger population of patients and controls. MIF expression in lung tissue was also evaluated by immunohistochemistry. MIF was identified in all 2-DE gels of IPF patients and it was significantly increased compared to controls (p<0.05). This result was confirmed by ELISA: MIF concentrations were significantly higher in IPF patients than controls (p<0.001) and were directly correlated with neutrophil percentages (p=0.0095). Immunohistochemical analysis revealed enhanced expression in bronchiolar epithelium, alveolar epithelium, and fibroblastic foci. In conclusion, MIF is a pleiotropic cytokine that could be involved in the pathogenesis of IPF, being particularly abundant in BAL of these patients and mainly expressed in the areas of active fibrosis.

MIF homologues from a filarial nematode parasite synergize with IL-4 to induce alternative activation of host macrophages

Macrophage migration inhibitory factor (MIF) is a highly conserved cytokine considered to exert wide-ranging, proinflammatory effects on the immune system. Recently, members of this gene family have been discovered in a number of invertebrate species, including parasitic helminths. However, chronic helminth infections are typically associated with a Th2-dominated, counter-inflammatory phenotype, in which alternatively activated macrophages (AAMs) are prominent. To resolve this apparent paradox, we have analyzed the activity of two helminth MIF homologues from the filarial nematode Brugia malayi, in comparison with the canonical MIF from the mouse. We report that murine MIF (mMIF) and Brugia MIF proteins induce broadly similar effects on bone marrow-derived mouse macrophages, eliciting a measured release of proinflammatory cytokines. In parallel, MIF was found to induce up-regulation of IL-4R on macrophages, which when treated in vitro with MIF in combination with IL-4, expressed markers of alternative activation [arginase, resistin-like molecule alpha (RELM-alpha) or found in inflammatory zone 1, Ym-1, murine macrophage mannose receptor] and differentiated into functional AAMs with in vitro-suppressive ability. Consistent with this finding, repeated in vivo administration of Brugia MIF induced expression of alternative macrophage activation markers. As mMIF did not induce RELM-alpha or Ym-1 in vivo, alternative activation may require components of the adaptive immune response to Brugia MIF, such as the production of IL-4. Hence, MIF may accentuate macrophage activation according to the polarity of the environment, thus promoting AAM differentiation in the presence of IL-4-inducing parasitic helminths.

Structures of Leishmania major orthologues of macrophage migration inhibitory factor

Leishmania major, an intracellular parasitic protozoon that infects, differentiates and replicates within macrophages, expresses two closely related MIF-like proteins. To ascertain the roles and potential differences of these two Leishmania proteins, recombinant L. major MIF1 and MIF2 have been produced and the structures resolved by X-ray crystallography. Each has a trimeric ring architecture similar to mammalian MIF, but with some structurally distinct features. LmjMIF1, but not LmjMIF2, has tautomerase activity. LmjMIF2 is found in all life cycle stages whereas LmjMIF1 is found exclusively in amastigotes, the intracellular stage responsible for mammalian disease. The findings are consistent with parasite MIFs modulating or circumventing the host macrophage response, thereby promoting parasite survival, but suggest the LmjMIFs have potentially different biological roles. Analysis of the Leishmania braziliensis genome showed that this species lacks both MIF genes. Thus MIF is not a virulence factor in all species of Leishmania.

Macrophage migration inhibitory factor is critical to interleukin-5-driven eosinophilopoiesis and tissue eosinophilia triggered by Schistosoma mansoni infection

Macrophage migration inhibitory factor (MIF) participates in the pathogenesis of inflammatory diseases, including asthma, in which it enhances airway hypersensitivity and tissue eosinophilia. Herein, we investigated the role of MIF in eosinophilopoiesis and tissue eosinophilia using Schistosoma mansoni infection. MIF-deficient (Mif(-/-)) mice had similar numbers of adult worms, eggs, and granulomas compared to wild-type mice, but the size of granulomas was strikingly reduced due to smaller numbers of eosinophils. MIF did not affect the acquired response to infection, as Mif(-/-) mice produced normal amounts of Th2 cytokines and IgE. Nevertheless, recombinant MIF (rMIF) behaved as a chemoattractant for eosinophils, what could partially explain the reduced eosinophilia in infected Mif(-/-) mice. Moreover, the percentage of eosinophils was reduced in bone marrows of Mif(-/-) mice chronically infected with S. mansoni compared to wild type. Mif(-/-) had impaired eosinophilopoiesis in response to interleukin (IL)-5 and addition of rMIF to bone marrow cultures from IL-5 transgenic mice enhanced the generation of eosinophils. In the absence of MIF, eosinophil precursors were unable to survive the IL-5-supplemented cell culture, and were ingested by macrophages. Treatment with pancaspase inhibitor z-VAD or rMIF promoted the survival of eosinophil progenitors. Together, these results indicate that MIF participates in IL-5-driven maturation of eosinophils and in tissue eosinophilia associated with S. mansoni infection.

The role of macrophage migration inhibitory factor on glucose metabolism and diabetes

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine involved in many inflammatory reactions and disorders, and it has become evident that it also affects glucose homeostasis. The protein is produced by pancreatic beta cells and can promote the release of insulin. It also modulates glucose uptake, glycolysis and insulin resistance in insulin target cells such as the adipocyte, myocyte and cardiomyocyte. Possessing both immunological and endocrinological properties, MIF has been associated with the development of type 1 and type 2 diabetes, and it may be important in the setting of islet transplantation. The present review summarises our current knowledge, based on clinical and research data, on the impact of MIF on both physiological and pathological aspects of glucose metabolism.

Macrophage migration inhibitory factor (MIF) is critical for the host resistance against Toxoplasma gondii

Macrophage migration inhibitory factor (MIF) exerts either a protective or a deleterious role in the immune response to different pathogens. We analyzed herein the role of MIF in the host control of toxoplasmosis using MIF(-/-) mice backcrossed to either the BALB/c or the C57BL/6 genetic backgrounds. Both, wild-type (WT) BALB/c and MIF(-/-) BALB/c mice were susceptible to infection with highly virulent RH as well as moderately virulent ME49 strains of T. gondii. MIF(-/-) mice, however, showed greater liver damage and more brain cysts, produced less proinflammatory cytokines, and succumbed significantly faster than WT mice. Bone marrow-derived dendritic cells (BMDCs) from MIF(-/-) mice produced less interleukin-1beta, interleukin-12, and tumor necrosis factor-alpha than WT BMDCs after stimulation with soluble Toxoplasma antigen (STAg). Similar observations were made in CD11c(+) low-density cells isolated from the spleens of MIF(-/-) mice challenged with STAg. MIF(-/-) C57BL/6 mice succumbed to ME49 infection faster than their WT counterparts. C57BL/6 mice that succumbed to infection with the ME49 strain produced less MIF than resistant BALB/c mice similarly infected. Interestingly, an analysis of brains from patients with cerebral toxoplasmosis showed low levels of MIF expression. Together, these findings demonstrate that MIF plays a critical role in mediating host resistance against T. gondii.

Orthologs of macrophage migration inhibitory factor from parasitic nematodes

Chronic helminth infections are associated with modulation of host cellular immune responses, presumably to prolong parasite survival within the mammalian host. This phenomenon is attributed, at least in part, to the elaboration of parasite molecules, including orthologs of host cytokines and receptors, at the host-parasite interface. This review describes recent progress in the characterization of macrophage migration inhibitory factor (MIF) orthologs from parasitic nematodes. The roles of these molecules in parasite developmental biology and pathogenesis are discussed. Further knowledge of the species-specific activities and three-dimensional structures of human and parasitic nematode MIF molecules should make them ideal targets for drug- and/or vaccine-based strategies aimed at nematode disease control.

GABA (A) receptor subunits RNA expression in mice peritoneal macrophages modulate their IL-6/IL-12 production

The expression and functionality of the gamma aminobutyric acid A receptor (GABA(A)R) in mice macrophages was explored. Reverse Transcriptase-Polymerase Chain Reaction showed that macrophages express the GABA(A)R RNA for the alpha1, alpha2, beta3 and delta subunits, but not for the alpha5, beta1, beta2 and gamma3 subunits. The expression of alpha1 subunit was also revealed by confocal microscopy. LPS-stimulated macrophages significantly reduced their in vitro production of IL-6 and IL-12 after GABA adding to the culture medium. These results showed that BALB/c mice peritoneal macrophages express a functional subset of GABA(A)R subunits.

Structural and functional characterization of a secreted hookworm Macrophage Migration Inhibitory Factor (MIF) that interacts with the human MIF receptor CD74

Hookworms, parasitic nematodes that infect nearly one billion people worldwide, are a major cause of anemia and malnutrition. We hypothesize that hookworms actively manipulate the host immune response through the production of specific molecules designed to facilitate infection by larval stages and adult worm survival within the intestine. A full-length cDNA encoding a secreted orthologue of the human cytokine, Macrophage Migration Inhibitory Factor (MIF) has been cloned from the hookworm Ancylostoma ceylanicum. Elucidation of the three-dimensional crystal structure of recombinant AceMIF (rAceMIF) revealed an overall structural homology with significant differences in the tautomerase sites of the human and hookworm proteins. The relative bioactivities of human and hookworm MIF proteins were compared using in vitro assays of tautomerase activity, macrophage migration, and binding to MIF receptor CD74. The activity of rAceMIF was not inhibited by the ligand ISO-1, which was previously determined to be an inhibitor of the catalytic site of human MIF. These data define unique immunological, structural, and functional characteristics of AceMIF, thereby establishing the potential for selectively inhibiting the hookworm cytokine as a means of reducing parasite survival and disease pathogenesis.

Macrophage migration inhibitory factor is essential for allergic asthma but not for Th2 differentiation

Macrophage migration inhibitory factor (MIF) is increased in asthmatic patients and plays a critical role in the pathogenesis of asthma. We show here that mice lacking MIF failed to develop airway hyper-responsiveness (AHR), tissue eosinophilia, and mucus metaplasia. Analysis of the bronchoalveolar fluids revealed a substantial reduction of IL-13, eotaxin and cysteinyl-leukotrienes. The lack of these cardinal features of asthma in MIF(-/-) mice occurs regardless of high concentrations of IL-4 in the lung and OVA-specific IgE in the serum. Antigen-specific lymphocyte proliferation and IL-13 production were similarly increased in the draining lymph nodes of OVA-immunized and challenged MIF(-/-) mice compared to WT, but were reduced in the spleen of MIF(-/-), thus indicating differential roles of MIF in these compartments. Stimulation of naive CD4(+) cells with anti-CD3 antibody demonstrated that MIF(-/-) cells produced increased amounts of IFN-gamma and IL-4 compared to WT CD4(+) cells. Finally, treatment of sensitized BALB/c mice with neutralizing anti-MIF antibody abrogated the development of ARH and airway inflammation without affecting the production of Th2 cytokines or IgE. The present study demonstrates that MIF is required for allergic inflammation, adding important elements to our knowledge of asthma pathogenesis and suggesting that neutralization of MIF might be of therapeutic value in asthma.

Functional Characterization of the Plasmodium falciparum and P. berghei Homologues of Macrophage Migration Inhibitory Factor

Macrophage migration inhibitory factor (MIF) is a mammalian cytokine that participates in innate and adaptive immune responses. Homologues of mammalian MIF have been discovered in parasite species infecting mammalian hosts (nematodes and malaria parasites), which suggests that the parasites express MIF to modulate the host immune response upon infection. Here we report the first biochemical and genetic characterization of a Plasmodium MIF ( P MIF). Like human MIF, histidine-tagged purified recombinant P MIF shows tautomerase and oxidoreductase activities (although the activities are reduced compared to those of histidine-tagged human MIF) and efficiently inhibits AP-1 activity in human embryonic kidney cells. Furthermore, we found that Plasmodium berghei MIF is expressed in both a mammalian host and a mosquito vector and that, in blood stages, it is secreted into the infected erythrocytes and released upon schizont rupture. Mutant P. berghei parasites lacking P MIF were able to complete the entire life cycle and exhibited no significant changes in growth characteristics or virulence features during blood stage infection. However, rodent hosts infected with knockout parasites had significantly higher numbers of circulating reticulocytes. Our results suggest that P MIF is produced by the parasite to influence host immune responses and the course of anemia upon infection.

Nitric oxide contributes to host resistance against experimental Taenia crassiceps cysticercosis

The immune mechanisms that underlie resistance and susceptibility to cysticercosis are not completely understood. In this paper, using susceptible BALB/c mice and resistant STAT6-/-BALB/c mice, we have analyzed the role of nitric oxide (NO) in determining the outcome of murine cysticercosis caused by the cestode Taenia crassiceps. After T. crassiceps infection, wild-type BALB/c mice developed a strong Th2-like response, produced high levels of IgG1, IgE, IL-5, IL-4, and discrete levels of NO, and remained susceptible to T. crassiceps infection. In contrast, similarly infected BALB/c mice treated with N(omega)-nitro-L-arginine methyl ester (L-NAME, an inhibitor of NO synthase) mounted a similar immune response but with lower levels of NO and harbored nearly 100% more parasites than N(omega)-nitro-D-arginine methyl ester (D-NAME, inactive enantiomer)-treated mice. To further analyze the role of NO in murine cysticercosis, we treated STAT6-/-male mice (known to be highly resistant to T. crassiceps) with L-NAME during 8 weeks of infection. As expected, STAT6-/-mice mounted a strong Th1-like response, produced high levels of IgG2a, IFN-gamma, and IL-17, whereas their macrophages displayed increased transcripts of tumor necrosis factor (TNF)-alpha as well as inducible nitric oxide synthase (iNOS) and efficiently controlled T. crassiceps infection. However, STAT6-/-male mice receiving L-NAME mounted a similar immune response but with lower iNOS transcripts concomitantly with decreased levels of NO in sera and displayed significantly higher parasite burdens. These findings suggest that macrophage activation and NO production are effector mechanisms that importantly contribute in host resistance to T. crassiceps infection. The immune mechanisms that underlie resistance and susceptibility to cysticercosis are not completely understood. In this paper, using susceptible BALB/c mice and resistant STAT6-/-BALB/c mice, we have analyzed the role of nitric oxide (NO) in determining the outcome of murine cysticercosis caused by the cestode Taenia crassiceps. After T. crassiceps infection, wild-type BALB/c mice developed a strong Th2-like response, produced high levels of IgG1, IgE, IL-5, IL-4, and discrete levels of NO, and remained susceptible to T. crassiceps infection. In contrast, similarly infected BALB/c mice treated with N(omega)-nitro-L-arginine methyl ester (L-NAME, an inhibitor of NO synthase) mounted a similar immune response but with lower levels of NO and harbored nearly 100% more parasites than N(omega)-nitro-d-arginine methyl ester (D-NAME, inactive enantiomer)-treated mice. To further analyze the role of NO in murine cysticercosis, we treated STAT6-/-male mice (known to be highly resistant to T. crassiceps) with L-NAME during 8 weeks of infection. As expected, STAT6-/-mice mounted a strong Th1-like response, produced high levels of IgG2a, IFN-gamma, and IL-17, whereas their macrophages displayed increased transcripts of tumor necrosis factor (TNF)-alpha as well as inducible nitric oxide synthase (iNOS) and efficiently controlled T. crassiceps infection. However, STAT6-/-male mice receiving L-NAME mounted a similar immune response but with lower iNOS transcripts concomitantly with decreased levels of NO in sera and displayed significantly higher parasite burdens. These findings suggest that macrophage activation and NO production are effector mechanisms that importantly contribute in host resistance to T. crassiceps infection.

The role of macrophage migration inhibitory factor in lethal Listeria monocytogenes infection in mice

Macrophage migration inhibitory factor (MIF) has been characterized as a proinflammatory cytokine. Previous studies have indicated that MIF may play a beneficial role or a detrimental role in microbial infections, depending on pathogens. In this study, we investigated the role of MIF in Listeria monocytogenes infection. The MIF titers increased 6h after lethal L. monocytogenes infection but not in the sublethal infection. The elimination of bacteria from the spleens and livers was not affected by anti-MIF antibody (Ab) injection in the sublethal infection, whereas anti-MIF Ab treatment rescued mice from the lethal infection, suggesting that MIF plays a deteriorating role in lethal L. monocytogenes infection. Anti-MIF Ab treatment significantly augmented interleukin (IL)-10 production in the spleens and livers 24h after infection, suggesting that MIF might down-regulate IL-10 production. Although the administration of anti-IL-10 monoclonal Ab showed no significant effect on the bacterial growth in the organs, the bacterial infection was deteriorated by the combined administration of Abs against MIF and IL-10. On the other hand, anti-MIF Ab treatment also increased in the serum cortisol titer 6h after infection compared with the control immunoglobulin G-injected group. Depletion of endogenous IL-10 decreased serum cortisol titers. These results suggested that IL-10 and cortisol might be involved in the deteriorating effect of MIF on lethal L. monocytogenes infection.

Macrophage migration inhibitory factor contributes to host defense against acute Trypanosoma cruzi infection

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that is involved in the host defense against several pathogens. Here we used MIF-/- mice to determine the role of endogenous MIF in the regulation of the host immune response against Trypanosoma cruzi infection. MIF-/- mice displayed high levels of blood and tissue parasitemia, developed severe heart and skeletal muscle immunopathology, and succumbed to T. cruzi infection faster than MIF+/+ mice. The enhanced susceptibility of MIF-/- mice to T. cruzi was associated with reduced levels of proinflammatory cytokines, such as tumor necrosis factor alpha, interleukin-12 (IL-12), IL-18, gamma interferon (IFN-gamma), and IL-1beta, in their sera and reduced production of IL-12, IFN-gamma, and IL-4 by spleen cells during the early phase of infection. At all time points, antigen-stimulated splenocytes from MIF+/+ and MIF-/- mice produced comparable levels of IL-10. MIF-/- mice also produced significantly less Th1-associated antigen-specific immunoglobulin G2a (IgG2a) throughout the infection, but both groups produced comparable levels of Th2-associated IgG1. Lastly, inflamed hearts from T. cruzi-infected MIF-/- mice expressed increased transcripts for IFN-gamma, but fewer for IL-12 p35, IL-12 p40, IL-23, and inducible nitric oxide synthase, compared to MIF+/+ mice. Taken together, our findings show that MIF plays a role in controlling acute T. cruzi infection.

Macrophage migration inhibitory factor and glucocorticoid sensitivity

Glucocorticoids (GCs) are widely used in the treatment of inflammatory diseases including rheumatoid arthritis (RA). Treatment with GC is associated with significant dose-dependent side-effects. The pro-inflammatory cytokine macrophage migration inhibitory factor (MIF) has emerged in recent years as a candidate factor which could regulate GC sensitivity. MIF is induced by GC, and is able to override anti-inflammatory actions of GCs. In this review, we summarize the pro-inflammatory actions of MIF with respect to RA, describe the interactions between MIF and GC and examine new evidence, which identifies MIF as a specific target for steroid sparing.

Decreased circulating macrophage migration inhibitory factor (MIF) protein and blood mononuclear cell MIF transcripts in children with Plasmodium falciparum malaria

Plasmodium falciparum malaria remains one of the most frequently lethal diseases affecting children in sub-Saharan Africa, yet the immune mediators that regulate pathogenesis are only partially defined. Since macrophage migration inhibitory factor (MIF) is important for regulating innate immunity in bacterial and parasitic infections, circulating MIF and peripheral blood mononuclear cell (PBMC) MIF transcripts were investigated in children with acute falciparum malaria. Peripheral blood levels of MIF-regulatory cytokines and effector molecules, including interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, interleukin (IL)-12, IL-10, transforming growth factor (TGF)-beta1, bicyclo-prostaglandin (PG) E2, and nitric oxide synthase activity were also determined. Circulating MIF and PBMC MIF mRNA were significantly lower in children with acute malaria relative to healthy, malaria-exposed children. Peripheral blood MIF levels showed no association with either parasitemia or hemoglobin concentrations. Circulating MIF was, however, significantly associated with IL-12 and TGF-beta1. Multiple regression analyses revealed that IFN-gamma was the most significant predictor of peripheral blood MIF concentrations. These findings suggest that reduced MIF production may promote enhanced disease severity in children with falciparum malaria.

Role for macrophage migration inhibitory factor in asthma

Macrophage migration inhibitory factor (MIF) is an immunologic regulator that is expressed in inflammatory and autoimmune disorders. We investigated MIF's role in asthma using genetic approaches in a mouse model and in a cohort of asthma patients. Mice genetically deficient in MIF that were primed and aerosol-challenged with ovalbumin showed less pulmonary inflammation and lower airway hyperresponsiveness than genetically matched, wild-type controls. MIF deficiency also resulted in lower titers of specific IgE, IgG(1), and IgG(2a), and decreased pulmonary, T(H)2 cytokine levels. IL-5 concentrations were lower and corresponded to decreased eosinophil numbers in bronchoalveolar lavage fluid. T cell studies also showed a lower level of antigen-specific responses in MIF-KO versus wild-type mice. In an analysis of 151 white patients with mild, moderate, or severe asthma (Global Initiative for Asthma criteria), a significant association was found between mild asthma and the low-expression, 5-CATT MIF allele. Pharmacologic inhibition of MIF may be beneficial and could be guided by the MIF genotype of affected individuals.