Infection with Toxoplasma gondii reduces established and developing Th2 responses induced by Nippostrongylus brasiliensis infection

Oral infection of C57BL/6 mice with 100 cysts of the protozoan parasite Toxoplasma gondii results in the development of small intestinal Th1-type immunopathology. In contrast, infection with intestinal helminths results in the development of protective Th2-type responses. We investigated whether infection with the helminth Nippostrongylus brasiliensis influences the development of T. gondii-induced Th1 responses and immunopathology in C57BL/6 mice infected with T. gondii. Prior as well as simultaneous infection of mice with N. brasiliensis did not alter the course of infection with 100 cysts of T. gondii. Coinfected mice produced high levels of interleukin-12 (IL-12) and gamma interferon (IFN-gamma), developed small intestinal immunopathology, and died at the same time as mice infected with T. gondii. Interestingly, local and systemic N. brasiliensis-induced Th2 responses, including IL-4 and IL-5 production by mesenteric lymph node and spleen cells and numbers of intestinal goblet cells and blood eosinophils, were markedly lower in coinfected than in N. brasiliensis-infected mice. Similar effects were seen when infection with 10 T. gondii cysts was administered following infection with N. brasiliensis. Infection of C57BL/6 mice with 10 T. gondii cysts prior to coinfection with N. brasiliensis inhibited the development of helminth-induced Th2 responses and was associated with higher and prolonged N. brasiliensis egg production. In contrast, oral administration of Toxoplasma lysate prior to N. brasiliensis infection had only a minor and short-lived effect on Th2 responses. Thus, N. brasiliensis-induced Th2 responses fail to alter T. gondii-induced Th1 responses and immunopathology, most likely because Th1 responses develop unchanged in C57BL/6 mice with a prior or simultaneous infection with N. brasiliensis. Our findings contribute to the understanding of immune regulation in coinfected animals and may assist in the design of immunotherapies for human Th1 and Th2 disorders.     

T1-deficient and T1-Fc-transgenic mice develop a normal protective Th2-type immune response following infection with Nippostrongylus brasiliensis

The IL-1 receptor-related protein T1 is expressed on the surface of Th2, but not Th1 cells. Studies with anti-T1 monoclonal antibodies have suggested that T1 is critical for development of normal Th2-type responses. To elucidate the role of T1 in vivo, we generated T1-deficient mice and a T1-transgenic strain which secretes soluble T1-Fc fusion protein into the serum. These were analyzed for the Th2 immune response induced by infection with the parasitic nematode Nippostrongylus brasiliensis. Although Th2 cytokine production by lymph node cells was similar in all groups of N. brasiliensis-infected mice, a decrease in IL-5 production by lung lymphocytes was detected in both T1-deficient and T1-Fc-transgenic mice compared to control littermates. This difference in IL-5 production did not influence blood eosinophilia, but recruitment of eosinophils into lung tissue, especially in T1-Fc-transgenic mice was slightly decreased. However, induction of all other immune parameters was normal and both T1-deficient and T1-Fc-transgenic mice were able to clear the parasite infection within 12 days with kinetics similar to those in control mice. Therefore, in contrast to previous suggestions, we conclude that the T1 protein is not obligatory for normal development of Th2 immune responses.     

Chemokines and chemokine receptors in T-cell priming and Th1/Th2-mediated responses

T-cell priming occurs in the lymphoid tissue via T cell–dendritic cell interaction. Conversely, delayed-type hypersensitivity or allergic reactions can occur in any tissue, following interaction of T helper 1 (Th1) or Th2 cells with effector leukocytes. Here, Federica Sallusto and colleagues review the role played by chemokines and chemokine receptors in positioning T cells for the immune response.     

Mast cell responses in mesenteric lymph nodes to infection of rats with the nematode, Nippostrongylus brasiliensis

The number of mast cells and their distribution in rat mesentery lymph nodes were assessed after a primary infection and after several successive infections with the nematode, Nippostrongylus brasiliensis. Following primary infection with N. brasiliensis, two peaks in total mast cell counts were observed. An initial small increase was restricted to day 5 and to the region of entrance to the lymph node. During the second peak, a marked increase in the number of mast cells occurred after day 15, the majority of cells is migrating through the afferent lymphatics, and then advancing from the cortical to the medullary region. The number of cells found in the hilus always remained low, indicating that mast cells accumulate and degranulate within the lymphoid organ.

In rats infected several times with the nematode parasite, mast cell numbers were markedly increased and the distribution pattern was similar to that found on day 21 after a primary infection. The observation that the percentage of cells found in the capsule was rather low in these animals indicates that local proliferation might have contributed to the high mast cell counts.

     

Low-level infection with the nematode Nippostrongylus brasiliensis induces significant and sustained specific and non-specific IgE antibody responses in rats.

Specific and non-specific IgE antibody responses were studied in SD rats infected with between 5 and 2500 Nippostrongylus brasiliensis (NB) larvae. In rats with 2500 NB larvae, specific IgE antibody, measured by enzyme-linked immunosorbent assay (ELISA) using NB excretory/secretory substance as antigen, reached a peak at 4 weeks of infection and gradually declined. On the other hand, in rats infected with 10 or 100 NB larvae, specific IgE was induced at 4 weeks of infection and the level continued to rise until at least 8 weeks after infection. The level at 8 weeks was significantly higher in rats infected with 10 or 100 larvae than in rats infected with 2500 larvae. The results indicate that the low-level infection induced a much more sustained specific IgE response than that induced after heavy infection. However, the level of specific IgG was correlated with the dose of infection, and reached a plateau 6 weeks after infection. Total serum IgE increased significantly even in rats infected with five larvae, a dose which did not induce detectable specific IgE. The kinetics of the production of total IgE was different in rats with light and heavy infections. In rats infected with five or 10 larvae, total IgE increased slowly and reached a plateau 4 weeks after infection. On the other hand, rats infected with more than 500 larvae showed a remarkable rise in total IgE at 2 weeks of infection; this rise gradually declined thereafter. Six weeks after infection, total IgE levels were almost the same (2-3 micrograms/ml) in rats infected with 10-2500 NB larvae. These results show that low-level NB infection induces a significant and sustained specific and non-specific IgE response in rats.     

Multiple interleukin-18 injections promote both mouse Th1 and Th2 responses after sublethal Escherichia coli infection

Interleukin (IL)-18 is considered to induce exclusively the Th1 immune response but not the Th2 response in the presence of adequate IL-12 stimulation in bacterial infections. However, we demonstrate herein that multiple IL-18 injections to the mice not only enhance the early Th1 response but also stimulate the Th2 response later after viable Escherichia coli infection. Multiple IL-18 injections (three alternate-day injections) raised the serum interferon (IFN)-gamma level at 6 h and serum Th2 cytokine levels, such as IL-4, IL-10 and IL-13, at 48 h after infection, while a single IL-18 injection increased only the serum IFN-gamma level. Depletion of mouse CD4+ cells suppressed the IL-18-induced Th2 cytokines, IL-4, IL-10 and IL-13. In contrast, depletion of natural killer (NK)1.1+ cells reduced the IFN-gamma and IL-13 levels. Moreover, multiple IL-18 injections up-regulated the serum IgM level at 72 h after infection while a single IL-18 injection did not. Interestingly, neutralization of IL-4 but not IFN-gamma partially suppressed the increased serum IgM. Liver mononuclear cells (MNCs) from the mice treated with multiple IL-18 injections significantly increased more production of not only IFN-gamma but also Th2 cytokines and IgM by in vitro lipopolysaccharide (LPS) stimulation than those from the phosphate-buffered saline (PBS)-treated mice, while liver MNCs from the single IL-18-injected mice also increased IFN-gamma production but significantly suppressed IL-4 and IgM production compared to those from the PBS-treated mice. Our findings suggest that multiple injections of IL-18 up-regulate both the cellular and humoral innate immunities, thereby enhancing host defence against bacterial infections.     

Establishment of nematode infection despite increased Th2 responses and immunopathology after selective depletion of Foxp3+ cells

Here, we show that Treg limit intestinal pathology during nematode infection and that they control the onset and magnitude of the anti‐parasitic Th Th2 response. Using mice expressing the diptheria toxin receptor under the control of the foxp3 locus, we removed Foxp3⁺ Treg during the early phase of infection with Heligmosomoides polygyrus bakeri. Depletion of Treg in infected animals did not affect adult worm burden, but led to increased pathology at the site of infection. Infected, depleted mice displayed higher frequencies of activated CD4⁺ T cells and increased levels of the Th2 cytokines IL‐4 and IL‐13. The stronger parasite‐specific Th2 response was accompanied by higher levels of IL‐10. Only a moderate change in Th1 (IFN‐γ) reactivity was detected in worm‐infected, Treg‐depleted mice. Furthermore, we detected an accelerated onset of parasite‐specific Th2 and IL‐10 responses in the transient absence of Foxp3⁺ Treg. However, adult worm burdens were not affected by the increased Th2‐reactivity in Treg‐depleted mice. Hence, our data show that Treg restrict the onset and strength of Th2 responses during intestinal worm infection, while increasing primary Th2 responses does not necessarily lead to killing of larvae or accelerated expulsion of adult worms.     

Adoptive transfer of total and parasite-specific IgE responses in rats infected with Nippostrongylus brasiliensis.

Infection of rats with Nippostrongylus brasiliensis has both a parasite-specific and non-specific IgE stimulating effect. Both these responses can be adoptively transferred with thoracic duct lymphocytes (TDL) from infected rats. The character of the IgE response in the recipient rats was related to the stage after infection of the cell donors. TDL from hyperimmune rats adoptively transferred high serum titres of parasite-specific IgE to infected recipient rats and substantially increased the levels of total IgE. However, adoptive immunization with TDL from donors infected 10 days previously did not stimulate parasite-specific IgE and only slightly increased total IgE levels. After cell fractionation the sIg- cells from day 10 TDL increased the level of total IgE but not parasite-specific IgE whereas sIg- cells from hyperimmune TDL did not induce any IgE response unless given with sIg+ cells. The possible reasons for this are discussed.     

Differential expression of T-bet, a T-box transcription factor required for Th1 T-cell development, in peripheral T-cell lymphomas

We studied T-bet expression in 91 cases of peripheral T-cell lymphoma (PTCL) by immunostaining and found expression in 42 cases (46%), including all 5 lymphoepithelioid lymphoma cases and 12 (86%) of 14 angioimmunoblastic lymphoma cases, but only 9 (25%) of 36 anaplastic large cell lymphoma cases. Expression of T-bet in PTCL correlates with expression of other markers of Th1 T-cell differentiation, including CXCR3 (P < .0001), CD69 (P = .0013), LEF-1 (P = .0007), and OX40/CD134 (P = .005), and absence of expression of markers of Th2 T-cell differentiation, including CD30 (P = .0001) and CXCR4 (P = .0144). Of 22 cases of PTCL immunoreactive for all Th1-associated markers previously studied and nonreactive for Th2-associated markers, 20 (91%) were immunoreactive for T-bet. Of 22 PTCL cases immunoreactive for Th2-associated markers studied and nonreactive for all Th1-associated markers studied, 4 (18%) were immunoreactive for T-bet. The remaining 47 PTCL cases (52%) exhibited incomplete or mixed staining for Th1- and Th2-associated markers, with 18 (38%) of 47 immunoreactive for T-bet. T-bet is a new marker that may contribute to the diagnosis and subtyping of PTCLs. T-bet expression in these neoplasms provides further support for a model of PTCL in which tumor subsets express markers of, and may be derived from, Th1- or Th2-committed T cells.     

Tumour necrosis factor, IL-1 and IL-6 in bronchoalveolar washings and their in vitro production during Nippostrongylus brasiliensis infection.

Bronchoalveolar washings (BAW) were obtained from rats primarily infected with N. brasiliensis during the early infection stage that coincides with the lung passage of the parasite and the recruitment of inflammatory cells. BAW were tested for IL-1, IL-6 and tumour necrosis factor (TNF) activities. We found that IL-1 production occurred only on day 1 post infection and ceased thereafter. IL-6 activity was present as from day 1 with a maximum on day 3 post infection and then returned to its normal levels on day 5 post infection. TNF activity was not recovered in BAW at any time of the early infection. Results obtained from the in vitro culture of BAW-adherent cells demonstrated that on day 1 post infection IL-1, but also large amounts of TNF were produced spontaneously, whereas IL-6 was continuously released. Bacterial lipopolysaccharide (LPS) stimulation of the cell culture resulted in an amplification of the cytokine production. Our results suggest that pulmonary cytokines detected in BAW were at least in part produced by alveolar macrophages. Furthermore, the kinetics of IL-1, TNF and IL-6 production show that these monokines are induced at different times during the course of infection, suggesting that cytokine production may follow different regulation patterns during the early phase of N. brasiliensis infection.     

Cytokine responses during mycobacterial and schistosomal antigen-induced pulmonary granuloma formation. Production of Th1 and Th2 cytokines and relative contribution of tumor necrosis factor.

Synchronized pulmonary granulomas (GRs) were induced in presensitized mice by intravenous embolization of polymer beads bound with purified protein derivative (PPD) of Mycobacteria tuberculosis or soluble antigens derived from Schistosoma mansoni eggs (SEA). Uncoated beads served as a foreign body control (CON). Antigen-coated beads elicited GRs with characteristic epithelioid macrophages and multinucleate giant cells by 4 days after embolization. Unlike PPD GR, SEA bead lesions contained eosinophils, whereas CON beads elicited only a limited mononuclear infiltrate. GRs and draining lymph nodes (LN) were assessed on days 2, 4, and 8 for Th1-(interleukin-2 [IL-2], interferon-gamma[IFN] and Th2-type (IL-4, IL-5, and IL-10) cytokines. CON GR produced only a small amount of IFN-gamma on day 2 and failed to induce a significant response in draining LN. In contrast, both PPD and SEA antigen-coated beads induced reactive lymphoid hyperplasia but differed greatly in local and regional cytokine profiles. PPD GR produced IFN-gamma on day 2 and the draining LN produced predominantly Th1 cytokines on days 2 and 4. In contrast, SEA beads GRs were dominated by Th2 cytokines. The corresponding LN produced IL-2 and IL-4 on day 2; IL-2, IL-4, IFN-gamma, and IL-10 on day 4; then IL-2, IFN-gamma, and IL-4 on day 8, probably reflecting maturational changes of T cells. Macrophages (MP) from bead GR also showed different patterns of IL-6 and tumor necrosis factor (TNF) production. Compared with CON GR, MPs from PPD GR were weak sources of IL-6, whereas those of SEA GR showed enhanced and accelerated production. In contrast, MP of PPD GR had augmented TNF-producing capacity, whereas those of SEA GR showed delayed TNF production. In vivo depletion of TNF, respectively, caused 40 and 10% decreases in PPD GR and SEA GR but had no effect on CON GR area, indicating that TNF contributed to a greater degree to the PPD response. These data show that depending on the inciting agent, GR can be mediated by different cytokines. Characterization of inflammatory lesions by cytokine profiles should allow design of more rational therapeutic interventions.     

Leishmania donovani infection of a susceptible host results in CD4+ T-cell apoptosis and decreased Th1 cytokine production

The disease visceral leishmaniasis is caused by a protozoan parasite, Leishmania donovani and is characterized by depressed cell-mediated immunity (CMI) and unhindered parasite growth in a susceptible host. The opposite trend is observed in a resistant host. However, the mechanism of this loss of CMI during the progressive disease is unknown as yet. In this report, we demonstrate that more than 40% of CD4+ T cells from a susceptible host undergo apoptosis resulting in a significant decrease in interleukin (IL)-2 and interferon (IFN)-gamma secretion, leaving IL-4 secretion unaffected. These changes are not apparent in the case of CD4+ T cells derived from a resistant host. The data reported here suggest that experimental Leishmania donovani infection leads to selective deletion of the IL-2 and IFN-gamma-secreting cells but not Th2-like cells in a susceptible but not a resistant host.     

BALB/c小鼠感染弓形虫后Thl/Th2免疫漂移的实验研究

目的:动态分析BALB/c小鼠感染弓形虫后Thl/Th2免疫失衡及免疫漂移特点,并探讨转录因子T-bet和GA.TA-3在此过程中的改变及其意义.方法:90只BALB/c小鼠随机分为正常对照组30只,弓形虫感染组60只.于感染后奇数天每天处死感染组小鼠2只,对照组小鼠1只,采用ELISA法动态检测各组小鼠血清中IFN-γ和IL-4的水平,同时应用荧光定量PCR方法检测小鼠脾细胞中T-bet和GATA-3 mRNA的表达情况.结果:感染组小鼠中,血清IFN-γ于感染后第4天开始显著升高,第5~7天维持在高峰值,从第8天开始下降,第9天降至正常水平;IL-4于感染后第8天开始显著升高,第9天升至峰值,从第14天开始下降,第15天降至正常水平;脾细胞T-bet mRNA的表达在感染后第3天升高,第5天达高峰后于第9天降至正常水平;脾细胞GATA-3 mRNA的表达在感染后第7天升高,第11天达高峰,于第13天降至正常水平.正常对照组小鼠在实验期内IFN-γ、IL-4水平没有明显变化,维持在正常的较低水平.结论:BALB/c小鼠感染弓形虫后诱导的免疫应答在感染急性期(第1-8天)以Th1应答为主,第9至13天,宿主免疫应答以Th2细胞应答为主,之后Thl/Th2应答基本恢复平衡.Thl应答向Th2应答的漂移与T-bet和GATA-3 mRNA的表达相关并受其调控,Thl/Th2型免疫应答的发生时相和效应强度可能影响弓形虫感染的最终结局.     

Th2 responses predominate during the early phases of infection in patients with localized cutaneous leishmaniasis and precede the development of Th1 responses

Intralesional Th2 responses preceded the development of Th1 responses in localized cutaneous leishmaniasis due to Leishmania guyanensis. Although the number of parasites increased in Th2 lesions, no correlation was found between the levels of cytokine expression and the number of parasites. In contrast, the decreased number of parasites in Th1 lesions is negatively correlated to gamma interferon expression.     

TREM-1 amplifies corneal inflammation after Pseudomonas aeruginosa infection by modulating Toll-like receptor signaling and Th1/Th2-type immune responses

As a novel family of cell surface receptors, triggering receptors expressed on myeloid cells (TREMs) play an important role in inflammatory responses. However, the role of TREMs in the ocular immune system remains unknown. In this study, we examined the expression and function of TREM-1 in Pseudomonas aeruginosa keratitis, one of the most common sight-threatening ocular diseases. TREM-1 was significantly increased in human corneas after P. aeruginosa infection. Consistent with TREM-1 expression at the human ocular surface, TREM-1 levels (mRNA and protein) were also elevated in the infected corneas of C57BL/6 (B6) mice at 1, 3, and 5 days postinfection. To determine whether TREM-1 dictates the outcome of P. aeruginosa keratitis in susceptible mice, TREM-1 signaling in B6 mice was blocked with a soluble mTREM-1/Fc fusion protein. The results indicated that blockade of TREM-1 reduced the severity of corneal disease, polymorphonuclear neutrophil infiltration, Th1/proinflammatory cytokine expression and Toll-like receptor (TLR) activation but enhanced the production of Th2 cytokines, murine β-defensin 2 (mBD2), single Ig interleukin-1R-related molecule (SIGIRR), and ST2. Furthermore, we also used agonistic anti-mTREM-1 antibody to activate TREM-1 signaling in B6 mice and found that TREM-1 activation resulted in worsened disease and earlier corneal perforation in infected B6 mouse corneas and elevated production of proinflammatory cytokines and TLR signaling molecules but reduced expression of mBD2, SIGIRR, and ST2. To the best of our knowledge, this study provides the first evidence that TREM-1 functions as an inflammatory amplifier in P. aeruginosa keratitis by modulating TLR signaling and Th1/Th2 responses.