Differential CD86 and CD40 co-stimulatory molecules and cytokine expression pattern induced by Trypanosoma cruzi in APCs from resistant or susceptible mice

Differential aspects of the host immune response generated by Trypanosoma cruzi infection were examined in two different mouse strains, BALB/c (haplotype H2-Kd) which does not overcome the acute phase of the infection and C57BL/6 (haplotype H2-Kb) which survives to the acute phase. After infection an increase in CD3+ T cells was observed in both mouse strains in the peritoneal cavity. However, while the CD3+ T cells from the BALB/c mice showed an increase in the IL-4 cytokine expression level, the same type of cells from the C57BL/6 mice showed an increase in IFN-gamma expression. In addition, only the macrophages from the C57BL/6 mice were activated secreting IL-12 and TNF-alpha and producing, moreover, high levels of nitrites. It was observed that also after parasite infection the expression of macrophage and dendritic cells CD40 and CD86 co-stimulation molecules from the spleen were diminished in BALB/c but not in C57BL/6 mice. In correlation with this observation the macrophages from the spleen of infected BALB/c mice secreted lower concentrations of nitrites than the C57BL/6 mouse cells. Also, the spleen dendritic cells from infected BALB/c mice had a small potential to present alloantigens in contrast to that observed in the infected C57BL/6 mouse cells.     

Immune responses to Yersinia enterocolitica in susceptible BALB/c and resistant C57BL/6 mice: an essential role for gamma interferon.

Susceptibility of mice to infection with Yersinia enterocolitica has been shown to be related to neither the Ity locus encoding for resistance to Salmonella typhimurium and other pathogens nor the H-2 locus. Recent studies in our laboratory have demonstrated that T-cell-mediated immune responses are required for overcoming primary Yersinia infection. In the present study, we investigated the course of infection with Y. enterocolitica and the resulting immune responses in Yersinia-susceptible BALB/c and Yersinia-resistant C57BL/6 mice. In the early phase of infection, the clearance of the pathogen was comparable in both strains of mice, suggesting similar mechanisms of innate resistance. Splenic T cells from Yersinia-infected C57BL/6 mice exhibited marked proliferative responses and produced gamma interferon (IFN-gamma) upon exposure to heat-killed yersiniae. By contrast, the Yersinia-specific T-cell response in BALB/c mice was weak, and IFN-gamma production could not be detected before day 21 postinfection. T cells isolated from C57BL/6 mice 7 days after infection mediated immunity to Y. enterocolitica but those from BALB/c mice did not, while at 21 days postinfection T cells from both strains mediated protection. Neutralization of IFN-gamma abrogated resistance to yersiniae in C57BL/6 mice but to a far smaller extent in BALB/c mice. Administration of recombinant IFN-gamma or anti-interleukin-4 antibodies rendered BALB/c mice resistant to yersiniae, whereas this treatment did not significantly affect the course of the infection in C57BL/6 mice. These results indicate that the cellular immune response, in particular the production of IFN-gamma by Yersinia-specific T cells, is associated with resistance of mice to Y. enterocolitica.     

Role of IFN-γ in the establishment of anterior chamber-associated immune deviation (ACAID)-induced CD8+ T regulatory cells

Introduction of alloantigens into the AC induces a form of immune tolerance known as ACAID, which induces antigen-specific CD8+ Tregs, contributing to ocular immune privilege by down-regulating immune responses. Recent evidence suggests IFN-γ is needed for the suppressive function of CD8+ ACAID Tregs. This study tested the hypothesis that IFN-γ is needed for alloantigen-specific ACAID CD8+ Tregs to execute their suppressive function but is not required for the establishment of ACAID CD8+ Tregs. To address this hypothesis, ACAID was induced by injecting BALB/c spleen cells into the AC of WT C57BL/6 mice, IFN-γ(-/-) C57BL/6 mice, or anti-IFN-γ-treated WT C57BL/6 mice. LAT assays using C57BL/6 APCs as stimulators, CD4+ T cells from C57BL/6 mice previously immunized toward BALB/c alloantigens as effector cells, and IFN-γ-competent, IFN-γ(-/-), or IFN-γR(-/-) CD8+ Tregs were used to evaluate the suppressive function of CD8+ ACAID Tregs in response to IFN-γ. IFN-γ(-/-) mice or mice treated with anti-IFN-γ antibody prior to AC injection of alloantigen failed to develop ACAID. The suppressive function of IFN-γ(-/-) ACAID CD8+ Tregs was restored through the administration of exogenous IFN-γ. This suppressive responsiveness toward IFN-γ was CD8+ Treg-intrinsic, as CD8+ Tregs from IFN-γR(-/-) mice, which were primed in the AC with alloantigens, were not able to suppress alloantigen-specific DTH responses. These results indicate that IFN-γ is not needed for the induction of CD8+ ACAID Tregs but is required for ACAID Tregs to exert the suppression of allospecific DTH responses.     

Immune alterations in three mouse strains following 2-deoxy-D-glucose administration

Using 2-deoxy-D-glucose (2-DG)-induced stress, our laboratory has developed studies to define stress effects on immune responses. Here, we report effects of increasing doses of 2-DG on the immune response of BALB/c, C57BL/6 and BDF(1) mice 2 h after three injections of 0 to 2000 mg/kg of 2-DG. Female 4- to 5-week-old mice were euthanized and blood and spleens were collected. A suspension of partially purified mature T splenocytes was obtained by negative selection using J11.d2 antibodies. Glucose and corticosterone levels were measured in the plasma of each mouse. Splenocyte and mature T splenocyte suspensions were tested in in vitro proliferation assays with or without concanavalin A. Splenocytes were analyzed for the following cell-surface markers: CD3, TCR alpha/beta, CD4, CD8 and major histocompatibility complex (MHC) Class II. Significant increases in blood glucose levels were observed in C57BL/6 and BALB/c strains with the highest 2-DG dose (p<0.05). Corticosterone levels were higher in BDF(1) mice and C57BL/6 mice following the administration of 1000 and 2000 mg/kg of 2-DG, respectively (p<0.01). In vitro proliferation of mature T splenocytes in the presence of concanavalin A was decreased in BDF(1) (p<0.05) but not in BALB/c and C57BL/6 mice. In addition, in BDF(1) mice the decrease was highly correlated with an increase of CD3+ and TCR alpha/beta+ cells in the spleen. These results demonstrated high variability in the response of different mouse strains to 2-DG-induced stress.     

Genetically determined disparate innate and adaptive cell-mediated immune responses to pulmonary Mycobacterium bovis BCG infection in C57BL/6 and BALB/c mice

The current study was designed to investigate the impact of genetic heterogeneity on host immune responses to pulmonary intracellular infection by using two mouse strains of distinct genetic background, C57BL/6 and BALB/c mice, and a model intracellular pathogen, Mycobacterium bovis BCG. Upon infection, compared to C57BL/6 mice, BALB/c mice developed an earlier response of interleukin 12 (IL-12), gamma interferon (IFN-gamma), tumor necrosis factor alpha, and macrophage chemoattractive protein 1, and greater neutrophilic influx to the lung by days 7 and 14. However, the level of these cytokines at days 27, 43, and 71 was much lower in BALB/c mice than in C57BL/6 mice. The magnitude of cellular responses was also much lower in the lung of BALB/c mice around day 27. Histologically, while C57BL/6 mice developed lymphocytic granulomas, BALB/c mice displayed atypical granulomas in the lung. Of importance, the level of type 2 cytokines IL-4 and IL-10 remained low and similar in the lung of both C57BL/6 and BALB/c mice throughout. Furthermore, lymphocytes isolated from systemic and local lymphoid tissues of infected BALB/c mice demonstrated a markedly lower antigen-specific IFN-gamma recall response. While the number of mycobacterial bacilli recovered from both the lung and spleen of BALB/c mice was similar to that in C57BL/6 mice at day 14, it was higher than that in C57BL/6 mice at day 43. However, it was eventually leveled off to that in C57BL/6 counterparts later. These results suggest the following: (i) genetic heterogeneity can lead to differential innate and adaptive cell-mediated immune responses to primary pulmonary mycobacterial infection; (ii) it is the level of adaptive, but not innate, immune response that is critical to host resistance; and (iii) a lower type 1 immune response in BALB/c mice is not accompanied by a heightened type 2 response during pulmonary mycobacterial infection.     

人乳头瘤病毒18型E6、E7蛋白T细胞表位筛选

目的 筛选人乳头瘤病毒18型E6、E7蛋白在小鼠中的T细胞表位.方法 以重组痘苗病毒rVVJ18 E7、E6分别免疫C57BL/6和BALB/c小鼠,利用覆盖E6和E7蛋白全长序列的肽库或截短的多肽,用酶联免疫斑点方法 （ELISPOT）和细胞内因子染色检测其所诱发的细胞免疫反应.结果 重组痘苗病毒rVVJ18 E7、E6免疫的两种品系小鼠均可检测到E6肽库刺激产生的特异性细胞免疫反应,经筛选确定E667-75（KCIDFYSRI）为C57BL/6小鼠、E660-68（IPHAAGHKC）为BALB/c小鼠识别的CD8＋的T细胞表位.两种小鼠中均未检测到E7蛋白诱发的细胞免疫反应.结论 筛选到分别被BALB/c和C57BL/6小鼠识别的两条针对E6蛋白的不同T细胞表位,为今后评价HPV18疫苗中E6蛋白的细胞免疫效果提供了实验依据.     

Respiratory virus-induced regulation of asthma-like responses in mice depends upon CD8 T cells and interferon-gamma production

Respiratory virus infections can significantly influence the development of airway disease by both predisposing and exacerbating the developing lung immune environment. In contrast, the initiation of a more desirable anti-viral response may better prepare the local environment and protect it from developing an adverse long-term disease phenotype. BALB/c or C57BL/6 mice exposed to respiratory syncytial virus (RSV) infection at the same time as allergen sensitization were assessed for airway function, cytokine responses, and inflammatory parameters. Depending on the genetic strain of mouse used, BALB/c versus C57BL/6, RSV could differentially protect against the development of airway allergen responses. Although RSV was able to block allergen sensitization and induction of airway hyperresponsiveness and eosinophilic inflammation in C57BL/6 mice, the infection did not reduce the allergic responses in BALB/c mice. The alteration of airway responsiveness did not depend on the timing of RSV infection in C57BL/6 mice in conjunction to the allergen sensitization protocol. Neutralization experiments demonstrated that interferon-gamma contributed significantly to the RSV-induced airway attenuation of the allergic responses, whereas transfer of CD8 T cells from RSV-infected animals suggested that they were partially responsible for the altered environment. These data suggest that a respiratory viral infection impacts on the local lung environment and may reflect specific aspects of the hygiene hypothesis. However, the outcome of this interaction depends on the immunological response of the host.     

Angiostrongylus costaricensis infection in C57BL/6 mice: MHC-II deficiency results in increased larval elimination but unaltered mortality

During experimental Angiostrongylus costaricensis infections in several inbred mouse strains, genetic factors as well as different cytokine secretion patterns have recently been shown to play a role in the outcome of infection in terms of morbidity and mortality, e.g. BALB/c mice show a high and C57BL/6 mice a low mortality during the acute phase of infection. In this study, C57BL/6 MHC-II knockout mice infected with A. costaricensis did not show increased mortality during the acute phase of infection when compared with wild-type mice. Furthermore, MHC-II knockout mice showed a strongly diminished parasite-specific humoral and cellular immune response, which can be explained by the nearly complete lack of CD4+ T cells in the periphery. This defect in MHC-II genes, the lack of CD4+ T cells, and the resulting cellular and humoral unresponsiveness resulted in a three times higher output of first-stage larvae in feces compared with wild-type animals. The results indicate that during experimental A. costaricensis infection a parasite-specific immune response, directed via MHC-II molecules and CD4+ T cells, is not essential for the survival of C57BL/6 mice during the acute phase of infection, whereas the elimination of first-stage larvae seems to be regulated by a MHC-II- and CD4+ T-cell-dependent mechanism.     

Host resistance to primary and secondary Campylobacter jejuni infections in C57Bl/6 mice

Campylobacter jejuni has been known as a main causative agent of human enterocolitis for more than 30 years. This has prompted the research on defence mechanisms of the host involved. Although the humoral immune response to C. jejuni has been addressed in many studies, relatively little is known about the role of T lymphocytes in campylobacteriosis. The current study was based on in vivo T-cell subsets depletion to evaluate the role of CD4+ and CD8+ T lymphocytes in disseminated C. jejuni infection in C57BL/6 mice. Depletion of either CD8+ or CD4+ cells did not change the overall infection kinetics of primary campylobacteriosis. To assess the role of T cells in acquired immunity that develops during primary infection in C57BL/6 mice, in vivo depletions were performed during reinfection. Depletion of CD4+ cells did not have any effect on secondary infection kinetics, whereas depletion of CD8+ cells resulted in secondary liver infection that failed to resolve during the observed period. This study showed that both CD8+ and CD4+ T cells contribute to protection of C57BL/6 mice against C. jejuni. However, the predominant role resides in the CD8+ cell subpopulation. The exact mechanisms by which CD8+ cells operate during the course of campylobacteriosis will be the subject of our further research.     

Protective Immunity against Recurrent Staphylococcus aureus Skin Infection Requires Antibody and Interleukin-17A

Although many microbial infections elicit an adaptive immune response that can protect against reinfection, it is generally thought that Staphylococcus aureus infections fail to generate protective immunity despite detectable T and B cell responses. No vaccine is yet proven to prevent S. aureus infections in humans, and efforts to develop one have been hampered by a lack of animal models in which protective immunity occurs. Our results describe a novel mouse model of protective immunity against recurrent infection, in which S. aureus skin and soft tissue infection (SSTI) strongly protected against secondary SSTI in BALB/c mice but much less so in C57BL/6 mice. This protection was dependent on antibody, because adoptive transfer of immune BALB/c serum or purified antibody into either BALB/c or C57BL/6 mice resulted in smaller skin lesions. We also identified an antibody-independent mechanism, because B cell-deficient mice were partially protected against secondary S. aureus SSTI and adoptive transfer of T cells from immune BALB/c mice resulted in smaller lesions upon primary infection. Furthermore, neutralization of interleukin-17A (IL-17A) abolished T cell-mediated protection in BALB/c mice, whereas neutralization of gamma interferon (IFN-γ) enhanced protection in C57BL/6 mice. Therefore, protective immunity against recurrent S. aureus SSTI was advanced by antibody and the Th17/IL-17A pathway and prevented by the Th1/IFN-γ pathway, suggesting that targeting both cell-mediated and humoral immunity might optimally protect against secondary S. aureus SSTI. These findings also highlight the importance of the mouse genetic background in the development of protective immunity against S. aureus SSTI.     

IL‐4 and IL‐15 promotion of virtual memory CD8+ T cells is determined by genetic background

Virtual memory (VM) CD8⁺ T cells are present in unimmunized mice, yet possess T‐cell receptors specific for foreign antigens. To date, VM cells have only been characterized in C57BL/6 mice. Here, we assessed the cytokine requirements for VM cells in C57BL/6 and BALB/c mice. As reported previously, VM cells in C57BL/6 mice rely mostly on IL‐15 and marginally on IL‐4. In stark contrast, VM cells in BALB/c mice rely substantially on IL‐4 and marginally on IL‐15. Further, NKT cells are the likely source of IL‐4, because CD1d‐deficient mice on a BALB/c background have significantly fewer VM cells. Notably, this NKT/IL‐4 axis contributes to appropriate effector and memory T‐cell responses to infection in BALB/c mice, but not in C57BL/6 mice. However, the effects of IL‐4 are manifest prior to, rather than during, infection. Thus, cytokine‐mediated control of the precursor population affects the development of virus‐specific CD8⁺ T‐cell memory. Depending upon the genetic background, different cytokines encountered before infection may influence the subsequent ability to mount primary and memory anti‐viral CD8⁺ T‐cell responses.     

The capacity to produce IFN-gamma rather than the presence of interleukin-4 determines the resistance and the degree of susceptibility to Leishmania donovani infection in mice.

The immune response against Leishmania donovani infection has been investigated in one resistant mouse strain (C3H/HeJ) and three susceptible mouse strains (C57BL/6, BALB/c, and B10D2/n). In order to correlate the strain-specific course of infection with the individual T cell response phenotype, the ex vivo cytokine secretion patterns of splenic lymphocytes were assessed by ELISA (interferon-y [IFN-gamma], interleukin-4 [IL-4], IL-10) or by bioassay (IL-2). The strain-dependent differences in the course of infection correlated closely with the potency of T cells to produce IFN-gamma. C3H/HeJ mice produced high amounts of IFN-gamma before and during infection, whereas susceptible mice produced low amounts of IFN-gamma early during L. donovani infection. However, C57BL/6 mice, which recovered from the infection rapidly after the acute stage, developed marked IFN-gamma response within the first 30 days of infection. In contrast, in BALB/c and B10D2/n mice, the IFN-gamma production diminished during the acute stage, and this was associated with a delay in recovery and with subsequent switching into the chronic stage. Interestingly, CD8+ T cells contributed significantly to IFN-gamma production during this phase. In contrast to IFN-y, the levels of IL-4 in response to antigen or mitogen ex vivo were always very low. Moreover, neutralization of endogenous IL-4 in vivo by treatment with soluble murine IL-4 receptor did not result in significant decreases in the parasite burdens in spleen and liver but did cause a decrease in the serum IgE level of L. donovani-infected BALB/c mice. These results confirm that in visceral leishmaniasis a Thl-dominated immune response is protective against the L. donovani parasites and, furthermore, that the capacity to produce IFN-gamma rather than the presence of IL-4 determines the efficacy of the immune response in susceptible mice. The data show that CD8+ T cells represent an important source of IFN-gamma during L. donovani infection in susceptible mice, implying a role for this cell type in healing and development of protective immunity.     

Differences in innate immune responses correlate with differences in murine susceptibility to Chlamydia muridarum pulmonary infection

We investigated the phenotypic basis for genetically determined differences in susceptibility and resistance to Chlamydia muridarum pulmonary infection using BALB/c and C57BL/6 mice. Following C. muridarum intranasal inoculation, the intensity of infection was very different between BALB/c and C57BL/6 beginning as early as 3 days post‐infection. Intrapulmonary cytokine patterns also differed at early time‐points (days 2 and 4) between these two strains of mice. The early recruitment of neutrophils to lung tissue was greater in BALB/c than in C57BL/6 mice and correlated with a higher number of inclusion forming units (IFU) of C. muridarum. At day 12 post‐infection, BALB/c mice continued to demonstrate a greater burden of infection, significantly higher lung cytokine levels for tumour necrosis factor‐α and interleukin‐17 (IL‐17) and a significantly lower level for interferon‐γ than did C57BL/6 mice. In vitro, bone‐marrow‐derived dendritic cells (BMDCs) from BALB/c mice underwent less functional maturation in response to C. muridarum infection than did BMDCs from C57BL/6 mice. The BMDCs of BALB/c mice expressed lower levels of activation markers (CD80, CD86, CD40 and major histocompatibility complex class II) and secreted less IL‐12 and more IL‐23 than BMDCs from C57BL/6 mice. Overall, the data demonstrate that the differences exhibited by BALB/c and C57BL/6 mice following C. muridarum pulmonary infection are associated with differences in early innate cytokine and cellular responses that are correlated with late differences in T helper type 17 versus type 1 adaptive immune responses.     

Mouse strain differences in the chemokine response to acute lung infection with a murine gammaherpesvirus

Numerous mouse strain-based differences in the immune response and in susceptibility to numerous pathogens have been described, but it is not known if these differences extend to chemokine responses to viral infection of the lungs. To define mouse strain-based differences in the host chemokine response and susceptibility to infection with murine gammaherpesvirus-68 (MHV-68), we compared the induced chemokine response to MHV-68 infection in the lungs of BALB/c and C57BL/6 mice at 1-15 days post-infection. CC and CXC chemokines were induced in both BALB/c and C57BL/6 following infection but the level of chemokine induction was significantly higher in the BALB/c mice for all chemokines measured. In addition, interferon-gamma (IFN-gamma) was also induced to a significantly higher level in the lungs of BALB/c infected mice compared to C57BL/6 mice. Interestingly, viral gene expression was lower in the lungs of C57BL/6 mice during the acute phase of replication. Titers of infectious virus were also greater in BALB/c lungs, although they did not achieve statistical significance. In contrast, latent viral load in the spleen, as measured by quantitative real-time PCR, did not significantly differ between mouse strains, suggesting that the establishment of latency is not affected by the amount of virus present during acute infection. This data suggests that robust chemokine response and expression of IFN-gamma in the lungs of infected BALB/c mice does not correlate with increased resistance to infection. In addition, the significant differences in chemokine responses observed will be important factors to consider in future studies of viral pathogenesis using mouse models.     

Contrasting phenotypes of liver-infiltrating leucocytes isolated from MCMV-infected BALB/c and C57 BL/6 mice

We characterized liver-infiltrating leucocytes (LIL) from BALB/c and C57BL/6 mice 0-56 days after murine cytomegalovirus (MCMV) infection. Inflammation clears from C57BL/6 mice 4-5 weeks post infection (pi), but persists for several months in BALB/c mice. The LIL obtained were 60-80% Thy 1.2+ by flow cytometry. The percentage of CD8+ cells rose sharply in all mice 7 days pi, with little decrease in BALB/c mice by day 56. CD4-CD8-Thy 1.2+/TCR alpha beta + cells were more prevalent in LIL than lymph node cells (LNC) irrespective of MCMV infection, whilst infection increased the proportion of CD8+ L-selectin- LIL (but not LNC). LIL from both mouse strains demonstrated cytotoxic activity against YAC-1 cells, but only LIL from BALB/c mice proliferated spontaneously ex vivo 21 days pi, as measured by tritiated thymidine incorporation. BALB/c LIL produced IFN gamma and IgG2a 7-21 days pi, whilst IL-10 secretion was similar in both strains. Thus, persistent hepatitis in BALB/c mice is associated with activation and proliferation of intrahepatic leucocytes with some bias towards a Th1 response.     

Response of CD4+ and CD8+ T lymphocytes in the evolution of Leishmania (Viannia) shawi infection

Leishmania (Viannia) shawi was recently characterized, and there are no studies of immunopathological alterations induced by this parasite. BALB/c and C57BL/6 mice were infected in the footpad with L. (V.) shawi promastigotes. The lesions were monitored during 8?weeks post-infection (pi), and at each 2?weeks pi, immunohistochemistry of skin and lymph nodes has been performed to analyze the densities of CD4+ and CD8+ T lymphocytes as well as amastigote forms. In the skin, BALB/c mice presented higher amastigote densities than C57BL/6 mice; concerning lymphocytes, there are no significant differences between CD4+ T lymphocytes densities; however, C57BL/6 mice presented elevation in densities of CD8+ T cells latter in the infection. The elevation of amastigote densities in lymph nodes of BALB/c mice at 8?weeks pi could be a reflection of suppressed density of CD4+ T. On the other hand, elevated density of CD8+ T lymphocytes in lymph nodes of C57BL/6 seems to exert some degree of resistance compared to BALB/c mice. The present work indicates that CD8+ T lymphocyte can be a key component to generation of resistance in L. (V.) shawi infections.     

CD4(+) and CD8(+) cells are key participants in the development of recurrent herpetic stromal keratitis in mice

Ocular herpes simplex virus (HSV) infection results in an immune-mediated inflammation of the corneal stroma known as herpetic stromal keratitis (HSK). Recurrent HSK is a common cause of virus-induced corneal blindness in humans. The role of CD4(+) and CD8(+) T cell subsets in the disease pathogenesis is ill defined and varies with the virus strain and host genetic background. To examine the contribution of T cell subsets to corneal disease, we studied the development of recurrent HSK in CD4 or CD8 gene knockout (KO) mice ocularly infected with HSV-1 McKrae strain. Following UV-B induced viral reactivation, corneal opacity in latently infected BALB/c (HSV sensitive) CD4 and CD8 KO mice was reduced compared to infected BALB/c mice with normal genotype. In contrast, opacity in C57BL/6 (HSV resistant) CD4 and CD8 KO latent mice did not differ from genetically normal latent mice. Virus-induced corneal opacity was not demonstrable in C57BL/6 CD4/CD8 double KO mice. Increased viral shedding, measured by reactivation rate, days shedding or viral titers, occurred in CD4 KO mice of both strains. Our findings indicate that both CD4(+) and CD8(+) cells play a role in the immunopathogenesis of recurrent HSK, and their role is dependent upon the host genetic profile.     

Relative importance of CD4+ and CD8+ T cells in the resolution of Chlamydophila abortus primary infection in mice

The role of the specific cellular immune response is well established in Chlamydiaceae infections, but the importance of each T-cell subset seems to be species-dependent. This study was designed to clarify the role of T-cell subsets in the response to Chlamydophila abortus primary infection. C57BL/6 mice were depleted of CD4+ or CD8+, or both, by monoclonal antibody injections and subsequently infected with C. abortus. Mice were killed at intervals and samples were collected for bacteriological and histopathological analysis. Also carried out were spleen cell culture, cytokine quantification, immunolabelling for C. abortus antigen, and a TUNEL assay for apoptosis. CD8+ T cell-depleted mice all died within 12 days of C. abortus infection, while no mortality was observed in the other groups; surprisingly, CD4+ T cell-depleted mice showed lower morbidity (expressed as weight loss) than did a non-depleted (control) group. CD8+ T cell-depleted mice also differed from the other groups in showing a significantly higher chlamydial burden in the liver. CD8+ T cell-depleted mice also had a higher number of apoptotic cells in hepatic inflammatory foci and showed exacerbated IFN-gamma production by spleen cells after specific stimulation. Simultaneous depletion of both T-cell subpopulations led to a chronic infection, but not to early mortality. It is concluded that CD8+ T cells may play a role in the regulatory control of the CD4+ T-cell response and may have a direct cytotoxic or IFN-gamma-mediated effect on infected cells.     

Mucosal and systemic cellular immune responses induced by Toxoplasma gondii antigens in cyst orally infected mice.

This study was performed to determine the T-cellular immune responses following Toxoplasma gondii oral infection and to assess further toxoplasma antigens on their ability to stimulate in vitro mucosal and systemic T-cell immunity. Parasite-specific cellular immune responses in Peyer's patches (PP), in mesenteric lymph nodes (MLN) and in spleen (SPL) were investigated using a lymphoblastic transformation test following oral infection of mice with strain 76K cysts of T. gondii. An early toxoplasma sonicate-induced mucosal T-cell proliferation occurred in MLN and PP with a peak responsiveness on day 6 post-infection (PI) and rapidly reached background levels on day 7 PI in PP and on day 8 PI in mesenteric lymph nodes. A later splenic cellular blastogenesis was observed from day 28 PI and persisted throughout the experiment (day 91). At the time of T-cell proliferation, FACS analyses revealed a decrease in the relative percentages of CD4+ and CD8+ T cells with a predominance of CD8+ lymphocytes which leads to an inversion of the CD4/CD8 ratios. We found that CBA/J is a high responder mouse strain in the induction of mesenteric and splenic T-lymphocyte blastogenesis compared to the intermediate responder BALB/c and low responder C57BL/6. Toxoplasma gondii antigens SAG1 (30,000 MW) and GRA4 (40,000-41,000 MW), which are known to induce locally IgA antibodies, are shown to stimulate primed mucosal T lymphocytes from CBA/J and BALB/c mice whereas no proliferation was demonstrated with C57BL/6 T cells. 229-242 peptide, derived from the deduced amino acid sequence of GRA4, only induces detectable proliferation of primed-CBA/J T lymphocytes. Following oral experimental infection, the in vitro mesenteric response to a toxoplasma sonicate is dominated by a Th2-type cytokine pattern whereas a predominant Th1 cytokine response is observed in the spleen. Finally, in vitro stimulation of mesenteric T cells with the three defined toxoplasma antigens resulted in secretion of interleukin-5 (IL-5) and IL-6 (except for SAG1) and interferon-gamma (IFN-gamma) whereas no detectable IL-2 or IL-4 was observed.     

Genetically programmed biases in Th1 and Th2 immune responses modulate atherogenesis

Atherosclerotic lesions contain T lymphocytes, which orchestrate adaptive immunity and regulate many innate immune pathways. This study examined the influence of Th1 and Th2 helper cell subsets on atherogenesis in two ApoE(-/-) mouse strains, C57BL/6 and BALB/c, which display opposite T-cell subset polarizations. ApoE(-/-) BL/6 mice showed predominant Th1-like immune responses on polyclonal stimulation of splenic CD4(+) T cells and had IgG2a antibodies to oxidized low-density lipoprotein (a disease-related antigen) whereas ApoE(-/-) BALB/c mice displayed predominant Th2 responses by CD4(+) T cells and an IgG1 isotype response toward oxidized low-density lipoprotein. ApoE(-/-) BL/6 and BALB/c mice consumed a high-cholesterol diet for 10, 16, and 24 weeks with equivalent cholesterolemic responses. The Th1-slanted BL/6 mice developed significantly more atherosclerosis in the aortic root and abdominal aorta at all time points compared with BALB/c mice, supporting a proatherogenic role for Th1 response. Progression of atherosclerosis was associated with increased levels of interleukin (IL)-6 in mouse serum and CD4(+) T-cell culture supernatants and increased levels of the acute-phase protein, serum amyloid A (SAA). Both IL-6 and SAA levels rose significantly in ApoE(-/-) BL/6 mice compared with BALB/c mice. The circulating cytokine milieu (IL-6) and acute phase reactants such as SAA may reflect alterations in the Th1/Th2 balance. The results presented here illustrate how genetically determined modifiers of both immune and inflammatory responses can modulate atherogenesis independently of lipid levels.