Miriam Rodriguez-Sosa

Chronic Helminth Infection Induces Alternatively Activated Macrophages Expressing High Levels of CCR5 with Low Interleukin-12 Production and Th2-Biasing Ability

ABSTRACT Helminth infections induce Th2-type biased immune responses. Although the mechanisms involved in this phenomenon are not yet clearly defined, antigen-presenting cells (APC) could play an important role in this process. Here, we have used peritoneal macrophages (F4/80+) recruited at different times after challenge with Taenia crassiceps as APC and tested their ability to regulate Th1/Th2 differentiation. Macrophages from acute infections produced high levels of interleukin-12 (IL-12) and nitric oxide (NO), paralleled with low levels of IL-6 and prostaglandin E2 (PGE2) and with the ability to induce strong antigen-specific CD4+ T-cell proliferation in response to nonrelated antigens. In contrast, macrophages from chronic infections produced higher levels of IL-6 and PGE2 and had suppressed production of IL-12 and NO, associated with a poor ability to induce antigen-specific proliferation in CD4+ T cells. Failure to induce proliferation was not due to a deficient expression of accessory molecules, since major histocompatibility complex class II, CD40, and B7-2 were up-regulated, together with CD23 and CCR5 as infection progressed. These macrophages from chronic infections were able to bias CD4+ T cells to produce IL-4 but not gamma interferon (IFN-γ), contrary to macrophages from acute infections. Blockade of B7-2 and IL-6 and inhibition of PGE2 failed to restore the proliferative response in CD4+ T cells. Furthermore, studies using STAT6−/− mice revealed that STAT6-mediated signaling was essential for the expansion of these alternatively activated macrophages. These data demonstrate that helminth infections can induce different macrophage populations that have Th2-biasing properties.

Genetically Resistant Mice Lacking IL-18 Gene Develop Th1 Response and Control Cutaneous Leishmania major Infection

IL-18 has been shown to play a critical role in the development of a Th1 response and immunity against intracellular pathogens. To determine the role of IL-18 in the development of protective immunity against Leishmania major, we have analyzed the course of cutaneous L. major in IL-18-deficient C57BL/6 mice (IL-18−/−) compared with similarly infected wild-type mice (IL-18+/+). After L. major infection, IL-18−/− mice may develop larger lesions during early phase of infection but eventually will resolve them as efficiently as IL-18+/+ mice. By 2 wk after infection, although Ag-stimulated lymph node cells from L. major-infected IL-18+/+ and IL-18−/− mice produced similar levels of IFN-γ, those from IL-18−/− mice produced significantly more IL-12 and IL-4. By 10 wk after infection, both IL-18+/+ and IL-18−/− mice had resolved L. major infection. At this time, lymph node cells from both IL-18+/+ and IL-18−/− mice produced IL-12 and IFN-γ but no IL-4. Furthermore, administration of anti-IFN-γ Abs to IL-18−/− mice rendered them susceptible to L. major. These results indicate that despite the role IL-18 may play in early control of cutaneous L. major lesion growth, this cytokine is not critical for development of protective Th1 response and resolution of L. major infection.

Macrophage Migration Inhibitory Factor Plays a Critical Role in Mediating Protection against the Helminth Parasite Taenia crassiceps

ABSTRACT To determine the role of endogenous migration inhibitory factor (MIF) in regulation of immune response during murine cysticercosis caused by the helminth parasite Taenia crassiceps, we analyzed the course of T. crassiceps infection in MIF−/− BALB/c mice. MIF−/− mice were highly susceptible to T. crassiceps and developed significantly higher parasite loads compared to similarly infected MIF+/+ mice. Throughout the course of infection, Taenia crassiceps soluble antigen-stimulated spleen cells from both MIF+/+ and MIF−/− mice produced significant and comparable levels of interleukin-4 (IL-4), but those from MIF−/− mice produced significantly more IL-13, as well as gamma interferon (IFN-γ), suggesting that the susceptibility of MIF−/− mice to T. crassiceps was not due to the lack of IFN-γ production. Interestingly, low levels of both total and specific immunoglobulin G2a were observed in MIF−/− cysticercotic mice despite the high IFN-γ levels; in addition, peritoneal macrophages obtained from T. crassiceps-infected MIF−/− mice at different time points failed to respond efficiently to stimulation in vitro with lipopolysaccharide plus IFN-γ and produced significantly lower levels of IL-12, tumor necrosis factor alpha, and NO compared to those from MIF+/+ mice. These findings demonstrate that MIF plays a critical role in mediating protection against T. crassiceps in vivo. Moreover, these findings also suggest that impaired macrophage function rather than the lack of Th1 development may be responsible for mediating susceptibility to T. crassiceps.

Cutting Edge: Susceptibility to the Larval Stage of the Helminth Parasite Taenia crassiceps Is Mediated by Th2 Response Induced Via STAT6 Signaling

Using STAT6−/− BALB/c mice, we analyzed the role of STAT6-induced Th2 response in determining the outcome of murine cysticercosis caused by the helminth parasite Taenia crassiceps. After T. crassiceps infection, wild-type BALB/c mice developed a strong Th2-like response; produced high levels of IgG1, IgE, IL-4, as well as IL-13; and remained susceptible to T. crassiceps. In contrast, similarly infected STAT6−/− mice mounted a strong Th1-like response; produced high levels of IgG2a, IL-12, IFN-γ, as well as nitric oxide; and efficiently controlled T. crassiceps infection. These findings demonstrate that Th2-like response induced via STAT6-mediated signaling pathway mediates susceptibility to T. crassiceps and, furthermore, that unlike the case in most helminths, immunity against T. crassiceps is mediated by a Th1-like rather than Th2-like response.

Macrophage Migration Inhibitory Factor Contributes to Host Defense against Acute Trypanosoma cruzi Infection

ABSTRACT 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-γ), and IL-1β, in their sera and reduced production of IL-12, IFN-γ, 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-γ, 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.

Intact glycans from cestode antigens are involved in innate activation of myeloid suppressor cells

During helminthic infections, strong Th2 type‐biased responses concomitant with impaired cell‐proliferative responses to parasitic and unrelated antigens are major immunological hallmarks. Parasite glycan structures have been proposed to play a role in modulating these responses. To understand early events related to immune modulation during cestode infection, we have examined the role of intact glycans of antigens from Taenia crassiceps in the recruitment of innate cells. Soluble antigens from this cestode contained higher levels of carbohydrates than proteins. Intraperitoneal injection of the antigens rapidly recruited a cell population expressing F4/80+/Gr‐1+surface markers, which adoptively suppressed naïve T‐cell proliferation in vitro in response to anti‐CD3/CD28 MAb stimulation in a cell‐contact dependent manner. Soluble antigens with altered glycans by treatment with sodium periodate significantly reduced the recruitment of F4/80+/Gr1+cells, concomitantly their suppressive activity was abrogated, indicating that glycans have a role in the early activation of these suppressor cells. Using C3H/HeJ and STAT6‐KO mice, we found that expansion and suppressive activity of F4/80+Gr1+cells induced by T. crassiceps intact antigens was TLR4 and Th2‐type cytokine independent. Together with previous studies on nematode and trematode parasites, our data support the hypothesis that glycans can be involved on a similar pathway in the immunoregulation by helminths.

Over‐production of IFN‐γ and IL‐12 in AhR‐null mice

The aryl hydrocarbon receptor (AhR) is a ligand‐activated transcription factor that mediates toxicity of environmental pollutants such as 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin. The exposure to AhR agonists results in profound suppression of cellular and humoral immune responses and compromises host to infectious disease. Therefore, to define the role of AhR in the immune response, spleen cells from ovalbumin (OVA)‐immunized and naïve mice were removed and stimulated in vitro with either OVA or mitogen concanavalin‐A (Con A), respectively. Proliferation, CD19+, F4/80+, CD4+ and CD8+ T cells expansion and cytokines production were measured in C57BL/6‐AhR−/− mice (AhR−/−) and compared with immune response in similarly immunized age‐matched wild type (AhR+/+) mice. In response to OVA immunization, AhR−/− mice had similar levels of serum OVA‐specific IgG2a, IgG1, and IgG2b compared with AhR+/+ animals. However, AhR−/− mice showed splenomegalia and an increase in B cells. No changes were observed on proliferation and IL‐4 secretion, although AhR−/− cells produced more IFN‐γ and IL‐12 than AhR+/+ cells. Similar results were observed with Con A stimulation, a decrease on IL‐5 and no change on IL‐2 secretion were observed on AhR−/− cells compared with AhR+/+ cells in response to Con A stimulation. High levels of IFN‐γ mRNA were detected in AhR−/− lymphocytes, but IL‐4 mRNA levels in AhR−/− cells were similar to those in AhR+/+ mice. These data suggest that AhR may play an important role in the normal development and function of immune system by down‐regulating IFN‐γ and IL‐12 expression.

A STAT4-dependent Th1 response is required for resistance to the helminth parasite Taenia crassiceps

ABSTRACT To determine the role of STAT4-dependent Th1 responses in the regulation of immunity to the helminth parasite Taenia crassiceps, we monitored infections with this parasite in resistant mice lacking the STAT4 gene. While T. crassiceps-infected STAT4+/+ mice rapidly resolved the infection, STAT4−/− mice were highly susceptible to infection and displayed large parasite loads. Moreover, the inability of STAT4−/− mice to control the infection was associated with the induction of an antigen-specific Th2-type response characterized by significantly higher levels of Th2-associated immunoglobulin G1 (IgG1) and total IgE as well as interleukin-4 (IL-4), IL-10, and IL-13 than those in STAT4+/+ mice, who produced significantly more gamma interferon. Furthermore, early after infection, macrophages from STAT4−/− mice produced lower levels of the pro-inflammatory cytokines IL-12, tumor necrosis factor alpha, IL-1β, and nitric oxide (NO) than those from STAT4+/+ mice, suggesting a pivotal role for macrophages in mediating protection against cysticercosis. These findings demonstrate a critical role for the STAT4 signaling pathway in the development of a Th1-type immune response that is essential for mediating protection against the larval stage of T. crassiceps infection.

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‐1β, interleukin‐12, and tumor necrosis factor‐α 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.—Flores, M., Saavedra, R., Bautista, R., Viedma, R., Tenorio, E. P., Leng, L., Sánchez, Y., Juárez, I., Satoskar, A. A., Shenoy, A. S., Terrazas, L. I., Bucala, R., Barbi J., Satoskar, A. R., Rodriguez‐Sosa, M. Macrophage migration inhibitory factor (MIF) is critical for the host resistance against Toxoplasma gondii. FASEB J. 22, 3661–3671 (2008)

Macrophage migration inhibitory factor is a therapeutic target in treatment of non-insulin-dependent diabetes mellitus

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine involved in the pathogenesis of a variety of autoimmune inflammatory diseases. Here, we investigated the role of MIF in the pathogenesis of non‐insulin‐dependent diabetes mellitus (NIDDM) using MIF−/− mice and a mouse model of streptozotocin (STZ)‐induced NIDDM. Following single injection of STZ, MIF+/+ BALB/c mice showed a significant increase in blood glucose levels, developed polyuria, and succumbed to disease. In contrast, no such increase in blood glucose was observed in MIF −/− BALB/c mice treated with STZ. These mice produced significantly less inflammatory cytokines and resistin as compared with MIF+/+ mice and failed to develop clinical disease. Finally, oral administration of a smallmolecule MIF antagonist, CPSI‐1306, to outbred ICR mice following induction of NIDDM significantly lowered blood glucose levels in the majority of animals, which was also associated with a significant reduction in the levels of the proinflammatory cytokines IL‐6 and TNF‐α in the sera. Taken together, these results demonstrate that MIF is involved in the pathogenesis of NIDDM and is a therapeutic target to treat this disease.—Sanchez‐Zamora, Y., Terrazas, L. I., Vilches‐Flores, A, Leal, E., Jua´rez, I., Whitacre, C, Kithcart, A., Pruitt, J., Sielecki, T., Satoskar, A. R, Rodriguez‐Sosa, M. Macrophage migration inhibitory factor is a therapeutic target in treatment of non‐insulin‐dependent diabetes mellitus. FASEB J. 24, 2583–2590 (2010). www.fasebj.org