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1.
We have investigated the possibility that nitric oxide (NO) synthesis may affect the course of a trypanosome infection via T-cell responses using mice deficient in inducible NO synthase (iNOS). Parasitemia levels increased at the same rate in both iNOS-deficient homozygous and control heterozygous mice, and peak parasitemia values were the same in both groups. However, the heterozygous mice maintained higher parasitemia levels after the peak of an infection than the homozygous mice due to a decrease in the rate of clearance of parasites. In iNOS-deficient mice there was an increase in the numbers of total CD4(+) cells and activated (interleukin-2 receptor-expressing) CD4(+) cells in infected mice compared with the numbers in uninfected mice. Spleen cells from infected iNOS-deficient mice displayed increased proliferative responses and gamma interferon secretion when stimulated in vitro than those of control mice. These data suggest that NO production depresses T-helper 1-like responses generated during Trypanosoma brucei infections, thus promoting the survival of the parasite.  相似文献   

2.
Epidemiological and experimental studies have indicated that helminth infections can ameliorate autoimmune diseases. The present study investigated the amelioration effect of the Trichinella pseudospiralis infection on experimental autoimmune encephalomyelitis (EAE), a T-cell-mediated autoimmune disease of central nervous system (CNS), and expression kinetics of Th17 and Th1 cytokine which play a crucial role in the pathogenesis of EAE. The results indicated that the infection of helminth T. pseudospiralis obviously ameliorated clinical severity and greatly delayed the onset of EAE induced by myelin oligodendrocyte glycoprotein (MOG) immunization. Infection caused much lesser inflammatory infiltration and demyilination in the CNS of infected EAE mice than uninfected EAE mice. The reduced infiltration was also suggested by the expressions of the inflammation cytokines, IL-17, IL-6, IL-1β, IFN-γ, and TNF-α, which were high in the spinal cords of the uninfected EAE mice, but was nearly normal or low in the infected EAE mice. The increased production of MOG-induced IL-17 and IFN-γ and the expression of IL-6, IL-1β, TGF-β in splenocytes after restimulation with MOG was inhibited in the infected EAE mice. On the other hand, the greatly induced Th2 response was observed in the splenocytes of the infected EAE mice. The present study showed that T. pseudospiralis infection can suppresses EAE by reducing the inflammatory infiltration in CNS, likely associated with the suppression of Th17 and Th1 responses by the infection.  相似文献   

3.
During Trypanosoma brucei infections, the response against the variant surface glycoprotein (VSG) of the parasite represents a major interaction between the mammalian host immune system and the parasite surface. Since immune recognition of other parasite derived factors also occurs, we examined the humoral host response against trypanosome heat shock protein 60 (HSP60), a conserved antigen with an autoimmune character. During experimental T. brucei infection in BALB/c mice, the anti-HSP60 response was induced when parasites differentiated into stumpy forms. This response was characterized by a stage-specific immunoglobulin isotype switching as well as by the induction of an autoimmune response. Specific recognition of trypanosome HSP60 was found to occur during the entire course of infection. Immunoglobulin G2a (IgG2a) and IgG2b antibodies, induced mainly in a T-cell-independent manner, were observed during the first peak of parasitemia, whereas IgG1 and IgG3 antibodies were found at the end of the infection, due to a specific T-cell-mediated response. Comparative analysis of the kinetics of anti-HSP60, anti-invariant surface glycoprotein 70 (ISG70), and anti-VSG antibody responses indicated that the three trypanosome antigens give rise to specific and independent patterns of immunoglobulin isotype switching.  相似文献   

4.
African trypanosomiasis is accompanied by profound general immunosuppression. The experiments described here were designed to characterize the contribution of macrophages to the immune pathology of this disease. We used peptone-stimulated, uninfected mice and injected them intraperitoneally with lethally irradiated and 35S-labeled Trypanosoma brucei and parasite-specific antisera. Peritoneal macrophages were thus induced to take up in vivo a defined number of trypanosomes. After the phagocytosis of parasites, macrophages were transferred into uninfected syngeneic mice, where they mimicked some of the important immunological changes normally associated with active trypanosome infection: (i) splenic background plaque-forming cells increased nonspecifically and (ii) the specific immune response to sheep erythrocytes was either enhanced or suppressed, depending on the timing of the antigen challenge: priming simultaneously with the transfer of trypanosome-containing macrophages enhanced immune responsiveness; in contrast, if parasite-containing macrophages were transferred and recipient mice were primed 4 days later, the immune response was suppressed. A contribution of suppressor T cells was ruled out by the treatment of peritoneal exudate cells with anti-Thy 1.2 and complement before transfer into recipient mice. The results indicate that macrophages are key cells in the mediation of parasite-induced immune dysfunction.  相似文献   

5.
A procedure which results in the specific activation of primed murine T lymphocytes was adapted for the study of T lymphocyte activation by the African trypanosome: Trypanosoma brucei. The assay calls for the in vivo priming of lymphocytes by the subcutaneous administration of parasites, followed by the co-cultivation in vitro of cells taken from the regional draining lymph nodes and the parasite. This co-cultivation results in a marked proliferation of lymphoid cells. The proliferation was shown to be specific for the parasite, and to be dependent on the presence of T lymphocytes and macrophages. Both the in vivo priming and the in vitro activation were shown to require the presence of living parasites. Various factors influencing the magnitude of the proliferative response were analysed. Of special interest is the observation that the time interval between in vivo priming and in vitro culture which results in a substantial proliferative response is quite short when compared to that seen with other antigens. Although lymph node cells from mice primed with T. brucei 1 to 2 weeks previously are able to mount a secondary proliferative response upon stimulation with T. brucei, cells taken 3 weeks after priming are unresponsive to an in vitro challenge with T. brucei. This unresponsiveness may be a result of the generalized immunosuppression seen in African trypanosomiasis. Thus, this method offers the potential for the study of specific T cell responsiveness in African trypanosome infections.  相似文献   

6.
目的:观察NKT细胞在实验性自身免疫性脑脊髓炎(EAE)小鼠脾脏和肝脏中所占百分比的变化特点,探讨NKT细胞在EAE模型中的免疫调节作用.方法:以MOG35-5521肽诱导C57BL/6小鼠建立EAE模型并进行临床评分.于发病高峰期处死小鼠,分离脾脏和肝脏淋巴细胞,采用免疫荧光染色和流式细胞术(FCM)分析,观察EAE小鼠与正常小鼠脾脏和肝脏中NKT细胞在全部淋巴细胞中所占百分率的变化.结果:在EAE小鼠不同器官中,NKT细胞占淋巴细胞的百分率均较正常小鼠减少.脾脏NKT细胞百分率(%)从正常组2.22±0.14下降到EAE模型组1.94±0.07(P<0.05),肝脏NKT细胞百分率(%)从正常组5.52±2.17下降到2.67±1.41(P<0.05).结论:NKT细胞在EAE模型C57BL/6小鼠脾脏和肝脏中增殖受抑,提示EAE发病可能通过对NKT细胞数量的调节进而影响其对免疫应答的调节.  相似文献   

7.
Experimental autoimmune encephalomyelitis (EAE) is regarded as an animal model of the human autoimmune disease multiple sclerosis (MS). Autoreactive T cells are present in the peripheral T cell repertoire of healthy mice and mediate clinical autoimmune disease only after activation by immunization or pathogens and migrate into the central nervous system (CNS). Because it is not known whether autoreactive T cells are regulated differentially once entering the CNS we investigated cytokine regulation in T cells from peripheral lymphatic organs and from the inflamed CNS ex vivo obtained from SJL mice after inducing relapsing-remitting EAE with PLP peptide 139–151. We show here that during acute EAE, an interleukin-2 (IL-2) biased T cell response exists in the spleen, while an interferon-γ (IFN-γ) biased T cell response prevails in the CNS of mice with acute EAE. The IFN-γ biased phenotype was stable with optimized costimulation and even after in vitro stimulation with IL-2. After adoptive transfer into naïve syngeneic mice these T cells were only partially reversed to an IL-2 biased phenotype. These findings of our work suggest that a permanent effector phenotype of neuroantigen-specific T cells is finally acquired in the CNS in EAE.  相似文献   

8.
MS is an inflammatory CNS disorder, which typically occurs in early adulthood and rarely in children. Here we tested whether functional maturation of innate immune cells may determine susceptibility to CNS autoimmune disease in EAE. Two‐week‐old mice were resistant to active EAE, which causes fulminant paralysis in adult mice; this resistance was associated with an impaired development of Th1 and Th17 cells. Resistant, young mice had higher frequencies of myeloid‐derived suppressor cells and plasma‐cytoid DCs. Furthermore, myeloid APCs and B cells from young mice expressed lower levels of MHC class II and CD40, produced decreased amounts of proinflammatory cytokines, and released enhanced levels of anti‐inflammatory IL‐10. When used as APCs, splenocytes from 2‐week‐old mice failed to differentiate naive T cells into Th1 and Th17 cells irrespective of the T‐cell donor's age, and promoted development of Treg cells and Th2 cells instead. Adoptive transfer of adult APCs restored the ability of 2‐week‐old mice to generate encephalitogenic T cells and develop EAE. Collectively, these findings indicate that the innate immune compartment functionally matures during development, which may be a prerequisite for development of T‐cell‐mediated CNS autoimmune disease.  相似文献   

9.
The essential role of Toll-like receptors (TLR) in innate immune responses to bacterial pathogens is increasingly recognized, but very little is known about the role of TLRs in host defense against infections with eukaryotic pathogens. For the present study, we investigated whether TLRs contribute to the innate and acquired immune response to infection with the intracellular protozoan parasite Leishmania major. Our results show that TLR4 contributes to the control of parasite growth in both phases of the immune response. We also addressed the mechanism that results in killing or growth of the intracellular parasites. Control of parasite replication correlates with the early induction of inducible nitric oxide synthase in TLR4-competent mice, whereas increased parasite survival in host cells from TLR4-deficient mice correlates with a higher activity of arginase, an enzyme known to promote parasite growth. This is the first study showing that TLR4 contributes to the effective control of Leishmania infection in vivo.  相似文献   

10.
After primary immunization with myelin/oligodendrocyte glycoprotein, CD28(-/-) mice developed experimental autoimmune meningitis (EAM) rather than experimental autoimmune encephalomyelitis (EAE). Cytokine and chemokine production in EAE and EAM were compared to understand the differences in disease phenotype. T cells from the central nervous system lesions of mice with either EAE or EAM expressed intracellular TNF-alpha. Splenic T cells from mice with EAM produced TNF-alpha and IL-6 but no IL-2. Conversely, EAE-derived splenic T cells produced TNF-alpha and IL-2 but no IL-6. Altered T cell differentiation in EAM was not due to a Th1 to Th2 shift, because equivalent amounts of T cell IFN-gamma mRNA were produced in both diseases. Neutrophils also produced inflammatory mediators such as TNF-alpha and IL-6 in EAM. Autocrine production of MIP-2 mRNA was observed in neutrophils from mice with EAM but not EAE. Therefore, distinct patterns of cytokines and chemokines distinguish EAE and EAM.  相似文献   

11.
Parasitic infections frequently lead to immune deviation or suppression. However, the application of specific parasitic molecules in regulating autoimmune responses remains to be explored. Here we report on the immune modulatory function of Lacto-N-fucopentaose III (LNFPIII), a schistosome glycan, in an animal model for multiple sclerosis. We found that LNFPIII treatment significantly reduced the severity of experimental autoimmune encephalomyelitis (EAE) and CNS inflammation, and skewed peripheral immune response to a Th2 dominant profile. Inflammatory monocytes (IMCs) purified from LNFPIII-treated mice had increased expression of nitric oxide synthase 2, and mediated T cell suppression. LNFPIII treatment also significantly increased mRNA expression of arginase-1, aldehyde dehydrogenase 1 subfamily A2, indoleamine 2,3-dioxygenase and heme oxygenase 1 in splenic IMCs. Furthermore, LNFPIII treatment significantly reduced trafficking of dendritic cells across brain endothelium in vitro. In summary, our study demonstrates that LNFPIII glycan treatment suppresses EAE by modulating both innate and T cell immune response.  相似文献   

12.
There is a large body of evidence demonstrating that DCs are the most efficient and specialized APCs for T‐cell priming, both in the context of host defense against pathogens and during the development of T‐cell‐mediated autoimmune responses; however, this concept is currently being challenged by a series of conflicting observations using genetically engineered mice in which DCs are either constitutively or inducibly ablated. In this issue of the European Journal of Immunology, Isaksson et al. [Eur. J. Immunol. 2012, 42: 2555‐2563] report the use of mice in which CD11chi cells can be ablated by injecting diphtheria toxin in vivo. The authors then induced EAE and found that, surprisingly, the mice were fully susceptible to the disease; thus, challenging the dogma that DCs are a mandatory APC population for the priming of autoimmune TH cells or T‐cell‐mediated immune responses. Here, we will analyze the authors’ findings in the context of observations made by others and critically discuss whether DCs can really be dismissed as crucial APCs.  相似文献   

13.
Experimental autoimmune encephalomyelitis (EAE) is an animal model for multiple sclerosis (MS) characterized by chronic inflammatory demyelination of the central nervous system (CNS). The pathology of EAE involves autoimmune CD4(+) T(h)1 cells. There is a striking inverse correlation between the occurrence of parasitic and autoimmune diseases. We demonstrate that in mice with Schistosoma mansoni ova immunization, the severity of EAE is reduced as measured by decreased clinical scores and CNS cellular infiltrates. Disease suppression is associated with immune deviation in the periphery and the CNS, demonstrated by decreased IFN-gamma and increased IL-4, transforming growth factor-beta and IL-10 levels in the periphery, and increased frequency of IL-4 producing neuroantigen-specific T cells in the brain. S. mansoni helminth ova treatment influenced the course of EAE in wild-type mice, but not in STAT6-deficient animals. This indicates that STAT6 plays a critical role in regulating the ameliorating effect of S. mansoni ova treatment on the autoimmune response, and provides the direct link between helminth treatment, T(h)2 environment and improved EAE. As some intestinal helminthic infections induce minimal pathology, they might offer a safe and inexpensive therapy to prevent and/or ameliorate MS.  相似文献   

14.
Innate immune mechanisms essential for priming encephalitogenic T cells in autoimmune neuroinflammation are poorly understood. Experimental autoimmune encephalomyelitis (EAE) is a IL-17-producing Th (Th17) cell-mediated autoimmune disease and an animal model of multiple sclerosis. To investigate how upstream TLR signals influence autoimmune T cell responses, we studied the role of individual TLR and MyD88, the common TLR adaptor molecule, in the initiation of innate and adaptive immune responses in EAE. Wild type (WT) C57BL/6, TLR-deficient and MyD88-deficient mice were immunized with myelin oligodendrocyte glycoprotein (MOG) in CFA. MyD88(-/-) mice were completely EAE resistant. Purified splenic myeloid DC (mDC) from MyD88(-/-) mice expressed much less IL-6 and IL-23, and serum and T cell IL-17 were absent. TLR4(-/-) and TLR9(-/-) mice surprisingly exhibited more severe EAE symptoms than WT mice. IL-6 and IL-23 expression by mDC and Th17 responses were higher in TLR4(-/-) mice, suggesting a regulatory role of TLR4 in priming Th17 cells. IL-6 expression by splenocytes was higher in TLR9(-/-) mice. Our data suggest that MyD88 mediates the induction of mDC IL-6 and IL-23 responses after MOG immunization, which in turn drives IL-17-producing encephalitogenic Th17 cell activation. Importantly, we demonstrate that TLR4 and TLR9 regulate disease severity in MOG-induced EAE.  相似文献   

15.
Infection of mice with the malaria parasite Plasmodium vinckei vinckei is 100% lethal. However, after two infections followed by drug cure, BALB/c mice develop a solid immunity which is antibody independent but mediated by CD4+ T cells. To elucidate the mechanisms of this immunity, spleen cells from immune mice were challenged in vitro with lysates of P. vinckei-infected or uninfected erythrocytes. The parasite antigen induced proliferation of T cells from immune mice but not from nonimmune mice. When gamma interferon production by cells from immune mice was assayed at the single-cell level, 1 to 3 cells per 1,000 cells were found to release this cytokine when exposed to antigen. In contrast, the numbers of interleukin 4 (IL-4)-producing cells from both immune and control mice were < or = 4 per 10(6) cells, regardless of antigen exposure. Investigation in a bioassay showed that P. vinckei antigen induced the release of IL-4 from spleen cells of immune mice but not from those of control mice. Nevertheless, that IL-4 is of minor significance in this system is also suggested by the absence of elevation of immunoglobulin E levels in blood samples from these mice, in contrast to what is seen with P. chabaudi infection, in which IL-4-producing Th2 cells are of major importance for immunity during later phases of infection. Taken together, the present results indicate that immunity to P. vinckei is a Th1 response, with gamma interferon being an important protective factor. Whether or not the Th1 response, through overproduction of tumor necrosis factor alpha, is also responsible for pathology and death in this infection remains to be clarified.  相似文献   

16.
 The growth of Trypanosoma brucei parasites in chronic infections was investigated by superimposing upon chronic infections, secondary infections in which all parasites expressed the same variable antigen type (VAT). The fate of trypanosomes in secondary infections could then be monitored using the VAT as a marker to discriminate cells in primary and secondary infections and thus enable growth to be observed separately from its interactions with antigenic variation on the part of the parasite and specific immune responses of the host. Our results show that as an infection proceeds, the growth rate is progressively inhibited in mice and sheep, suggesting that inhibition is a general feature of chronic infections. Inhibition was not specific to either the stock or the VAT of the trypanosome, but the degree of inhibition did vary between stocks. Inhibition appeared to be mediated by a lowering of the rate of replication of ’slender’-form parasites rather than by an increase in either the rate of differentiation from dividing slender to non-dividing ’stumpy’ forms or the mortality caused by non-specific immune mechanisms. Evidence indicated that the development of specific immune responses to non-variant parasite antigens was also unlikely. These data constitute, we believe, the first evidence for negative regulation of growth in vivo, which may be an important determinant of the virulence of trypanosome infections. Received: 10 March 1995 / Accepted: 25 May 1995  相似文献   

17.
The immature immune system requires constant stimulation by foreign antigens during the early stages of life to develop properly and to create efficient immune responses against later infections. We have previously shown that intake of antigenic dietary protein is critical for inducing maturation of the immune system as well as for the development of T helper type 1 (Th1) immunity. In this study, we show that administration of an amino acid (aa)‐based diet during the development of the immune system subsequently resulted in inefficient control of Leishmania major infection in adult C57BL/6 mice. Compared with mice fed a control protein‐containing diet, adult aa‐fed mice showed a decreased interferon (IFN)‐γ response to parasite antigens and insufficient production of nitric oxide (NO), which is crucial to parasite death. However, no deviation towards Th2‐specific immunity to L. major was observed. Phenotypic analysis of antigen‐presenting cells (APCs) from aa‐fed mice revealed deficient levels of the costimulatory molecules CD40 and CD80, and low levels of interleukin (IL)‐12 produced by peritoneal macrophages, revealing an early stage of maturation of these cells. APCs isolated from aa‐fed mice were unable to stimulate a Th1 response in vitro. Both phenotypic features of T cells from aa‐fed mice and their ability to produce a Th1 response in the presence of mature APCs were unaffected when compared with T cells from control mice. The results presented here support the notion that regulation of Th1 immunity to infection includes environmental factors such as dietary proteins, which provide a natural source of stimulation that contributes to the process of maturation of APCs.  相似文献   

18.
Experimental autoimmune encephalomyelitis (EAE), a model for the human disease multiple sclerosis (MS), is dependent upon the activation and effector functions of autoreactive CD4 T cells. Multiple interactions between CD4 T cells and major histocompatibility class II (MHCII)+ antigen presenting cells (APCs) must occur in both the periphery and central nervous system (CNS) to elicit autoimmunity. The identity of the MHCII+ APCs involved throughout this process remains in question. We investigated which APC in the periphery and CNS mediates disease using transgenic mice with MHCII expression restricted to dendritic cells (DCs). MHCII expression restricted to DCs results in normal susceptibility to peptide-mediated EAE. Indeed, radiation-sensitive bone marrow-derived DCs were sufficient for all APC functions during peptide-induced disease. However, DCs alone were inefficient at promoting disease after immunization with the myelin protein myelin oligodendrocyte glycoprotein (MOG), even in the presence of MHCII-deficient B cells. Consistent with a defect in disease induction following protein immunization, antigen presentation by DCs alone was incapable of mediating spontaneous optic neuritis. These results indicate that DCs are capable of perpetuating CNS-targeted autoimmunity when antigens are readily available, but other APCs are required to efficiently initiate pathogenic cognate CD4 T cell responses.  相似文献   

19.
Saliva and salivary gland extract (SGE) of Ixodes ricinus ticks have suppressive effects on the innate immune response of BALB/c mice. Tick saliva prevents hemolysis of sheep red blood cells (SRBC) by the human alternative pathway of complement. The adaptive immune response is also modulated by tick antigens (saliva or SGE). When stimulated in vitro with increasing doses of tick antigens, the proliferation and IL-4 production of draining lymph node T cells of mice infested with nymphal ticks increase, peak and then decrease. These results indicate that immunostimulative and immunosuppressive molecules have competing effects in tick saliva or in SGE. I. ricinus saliva inhibits, in a dose-dependent manner, splenic T cell proliferation in response to concanavalin A (ConA). Tick SGE or saliva injected intraperitoneally to BALB/c mice simultaneously with SRBC systemically immunosuppress the anti-SRBC response as shown in vitro by the reduced responsiveness of sensitized splenic T cells to restimulation with SRBC. In brief some components of SGE or tick saliva reduce the responsiveness of draining lymph node T cells and of sensitized splenic T cells in vitro. The responsiveness of naive splenic T cells to ConA stimulation in vitro is also decreased by tick saliva. Modulation of host responses by tick antigens may facilitate tick feeding, transmission and the propagation of pathogens.  相似文献   

20.
Dendritic cells (DC) are antigen-presenting cells specialized to regulate immune responses. DC not only control immunity, but also maintain tolerance to self-antigens-two complementary functions that would ensure the integrity of the organism in an environment full of pathogens. Here we report that splenic DC that had been exposed in vitro to IFN-gamma (IFN-gamma-DC) exhibit therapeutic potential on acute experimental allergic encephalomyelitis (EAE) in Lewis rats, and on chronic-relapsing EAE in B6 and SJL/J mice. During incipient EAE [day 5 post-immunization (p.i.) in rats, day 7 p.i. in mice], IFN-gamma-DC were injected s.c. Severity of clinical signs of EAE was dramatically inhibited in animals injected with IFN-gamma-DC, showing normal magnetic resonance imaging (MRI) of the spinal cord and brain. In contrast, the EAE rats receiving PBS or naive DC had severe clinical signs with multiple and extensive MRI lesions in the spinal cord and brain. IFN-gamma-DC triggered an antigen-specific IFN-gamma production, and induced apoptosis of CD4(+) T cells possibly through DC expressing indoleamine 2,3-dioxygenase and/or an IFN-gamma-dependent pathway. As a result, infiltration of macrophages and CD4(+) T cells within the spinal cords was dramatically reduced in animals injected with IFN-gamma-DC as compared to animals injected with PBS or naive DC. This approach may represent a novel possibility of individualized immunotherapy using autologous, in vitro modified DC as a complement to conventional therapy in multiple sclerosis and other diseases with an autoimmune background.  相似文献   

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