自然调节性T细胞对脑型疟疾易感鼠和抵抗鼠感染结局的影响

目的探讨自然调节性T细胞(nTregs)在伯氏疟原虫感染过程中的活化特点及其与疾病进展的相关性。方法用伯氏疟原虫ANKA分别感染C57BL/6、BALB/c和DBA/2小鼠,计数红细胞感染率;感染前和感染后3、5、8d制备脾细胞悬液,流式细胞术检测脾细胞悬液中nTregs百分含量;ELISA和Griess方法检测脾细胞培养上清IFN-γ、IL-10和NO水平。结果C57BL/6小鼠感染后8～11d死于脑疟,BALB/c和DBA/2小鼠感染后3～4w死于贫血和过度虫体血症。3种小鼠于感染后3d,nTregs百分数达到峰值后逐渐下降,于感染后8d,C57BL/6小鼠nTregs百分数下降最为显著并明显低于正常水平,整个感染过程中,C57BL/6小鼠的nTregs百分含量显著低于BALB/c和DBA/2小鼠。3种小鼠脾细胞培养上清IFN-γ、NO和IL-10水平于感染后开始升高,感染后5d达到峰值,感染后8d与感染后5d相比,C57BL/6小鼠IFN-γ、NO水平轻微下降,IL-10水平显著下降;BALB/c和DBA/2小鼠IFN-γ、NO水平显著下降,IL-10水平轻微下降。并且C57BL/6小鼠IFN-γ、NO水平高于BALB/c和DBA/2小鼠,而IL-10水平低于BALB/c和DBA/2小鼠。3种小鼠感染后脾脏nTregs数量与IFN-γ和NO水平呈负相关,IL-10水平与感染率呈正相关。结论伯氏疟原虫感染过程中,nTregs数量的动态变化与宿主感染结局密切相关。     

日本血吸虫重组谷胱甘肽-S-转移酶诱生的保护性免疫应答特征的研究

目的：研究日本血吸虫重组谷胱甘肽－Ｓ－转移酶（ｒｅＳｊｃ２６ＧＳＴ）在不同品系小鼠（ＢＡＬＢ／ｃ小鼠及Ｃ５７ＢＬ／６小鼠）诱生免疫应答的差异。方法：将ｒｅＳｊｃ２６ＧＳＴ（弗氏佐剂）经皮下免疫ＢＡＬＢ／ｃ小鼠及Ｃ５７ＢＬ／６小鼠,收集免疫前和免疫后血清及取小鼠脾脏,分析ｒｅＳｊｃ２６ＧＳＴ免疫小鼠诱生的特异性抗体、脾脏淋巴细胞特异性增殖能力及细胞因子种类等。结果：ｒｅＳｊｃ２６ＧＳＴ免疫Ｃ５７ＢＬ／６小鼠所诱生的抗体总ＩｇＧ及ＩｇＧ亚类均较明显高于免疫ＢＡＬＢ／ｃ小鼠。抗体ＩｇＧ亚类分析显示,ｒｅＳｊｃ２６ＧＳＴ在Ｃ５７ＢＬ／６小鼠诱生较高滴度的ＩｇＧ１和ＩｇＧ２ａ及ＩｇＧ２ｂ（血清按１∶４００稀释,Ａ４９２ｎｍ值分别为＞３．０、１．１２７、＞３．０）,而在ＢＡＬＢ／ｃ小鼠主要诱生较低滴度的ＩｇＧ１和ＩｇＧ２ａ及ＩｇＧ２ｂ（血清按１∶４００稀释,Ａ４９２ｎｍ值分别为１．１８９、０．３９、０．６２５）;ｒｅＳｊｃ２６ＧＳＴ免疫能够诱导小鼠Ｔｈ细胞激活。细胞因子分析显示ｒｅＳｊｃ２６ＧＳＴ免疫Ｃ５７ＢＬ／６小鼠既能诱生较高水平的ＩＬ－２及ＩＦＮ－γ,又能诱生ＩＬ－５。而ｒｅＳｊｃ２６ＧＳＴ免疫ＢＡＬＢ／ｃ小鼠仅     

ICOSL敲基因小鼠日本血吸虫病模型的免疫应答及其免疫病理

目的 观察ICOSL敲基因（ICOSL knockout,ICOSL-KO）小鼠感染日本血吸虫后的免疫应答及其免疫病理反应。方法 建立ICOSL-KO小鼠及野生型C57BL/6J小鼠日本血吸虫病模型,收集感染前（0周）和感染后（4~20周）的小鼠脾淋巴细胞用SEA进行诱导培养72小时后,采用ELISA双抗夹心法检测培养上清中Th1（IFN-γ、IL-12）及Th2（IL-4、IL-10、IL-13）细胞因子表达水平。应用ELISA法检测同期血清中SEA特异性抗体IgG、及其亚类IgG1、IgG2a的表达水平。应用HE染色法观察小鼠肝脏虫卵肉芽肿病变。 结果 ICOSL-KO小鼠Th1细胞因子IFN-γ、IL-12表达明显高于野生型小鼠,而其Th2型细胞因子（IL-4、IL-10、IL-13）表达水平却显著低于野生型小鼠。ICOSL-KO小鼠血清SEA特异性抗体IgG及其亚类IgG1、IgG2a的水平显著低于野生型C57BL/6J小鼠的水平,其Th2分化指数与IgG1/IgG2a的比值亦低于野生型小鼠的水平,特别是在感染7、12、16周后具有显著性差异。且ICOSL-KO小鼠的肝脏虫卵肉芽肿病变显著小于野生型小鼠。结论 感染日本血吸虫的ICOSL-KO小鼠Th2免疫应答显著下调并导致肝虫卵肉芽肿病变减弱,表明ICOS–ICOSL 信号通路在血吸虫病免疫病理中具有重要作用。     

In vitro indomethacin administration upregulates interleukin-12 production and polarizes the immune response towards a Th1 type in susceptible BALB/c mice infected with Leishmania mexicana

The immune response in Leishmania infected BALB/c mice is associated with a Th2 type cellular response, which has been characterized by the absence of interleukin (IL)-12, interferon (IFN)-gamma, and nitric oxide (NO) and the presence of IL-10 and IL-4. Prostaglandins (PGs) can modulate the immune response inhibiting the development of Th1 response and enhancing the development of Th2 response. We investigated the production of PGs and their effects on cytokine and NO production by spleen cells from Leishmania mexicana infected BALB/c and C57BL/6 mice. Increased production of PGs was noted as early as 1 week after infection in BALB/c mice, whereas in infected C57BL/6 mice PGs were not detected. In vitro administration of indomethacin (INDO), a specific inhibitor of PGs synthesis, reduced PGs production at normal levels, and increased IL-12, IFN-gamma, and NO production in infected BALB/c mice. Whereas, IL-10 and IL-4 were not affected. Moreover, INDO did not modulate cytokine and NO production in infected C57BL/6. INDO addition induced the intracellular killing of parasites in infected BALB/c mice. Together, these results suggest that suppression of PGs by INDO may promote the development of a protective Th1 type response in susceptible mice by a mechanism, which involves an enhancement of IL-12, IFN-gamma and NO production. These findings were confirmed by smaller lesions in BALB/c mice, when treated with INDO.     

Major histocompatibility complex restriction of T-cell suppression of immune response to mycobacteria.

In earlier work, intraperitoneal (i.p.) immunization with Mycobacterium vaccae was shown to generate a T-suppressor (Ts) response but intradermal (i.d.) immunization did not. We have now studied the major histocompatibility complex (MHC) restriction of this Ts response. The ability of C57BL/6 (H-2b), BALB/c (H-2d), and the (C57BL/6 x BALB/c) F1 mice to generate suppression after i.p. immunization with 10(8) killed M. vaccae was investigated. The BALB/c and the F1 mice generated suppression, but the C57BL/6 mice failed to do so. The suppression could be ascribed to Lyt-2+, L3T4- antigen-specific T cells. The F1 suppressors generated after i.p. immunization could suppress the generation of T-cell responses to i.d. immunization with M. vaccae in the parental BALB/c but not in the C57BL/6 mice. Monoclonal anti-I-A antibody could suppress the antigen-induced proliferative response of mice primed i.d. with M. vaccae. In contrast, monoclonal anti-I-E antibody enhanced antigen-specific proliferation of spleen cells primed i.p. with M. vaccae. The suppressors generated by i.p. priming of mice with M. vaccae could also suppress the in vitro antigen-induced proliferative response of i.d.-primed spleen cells; the suppression could be blocked by anti-I-E antibody. Thus, the T-cell-mediated suppression in the above experimental model was I-E restricted. The inability of the C57BL/6 mice to generate suppression after i.p. immunization with M. vaccae was ascribed to the lack of I-E expression by mice of H-2b strain.     

日本血吸虫22.6kDa膜相关蛋白Th1型表位的免疫学鉴定

目的鉴定日本血吸虫22.6 kDa膜蛋白（Sj22.6）的Th1型表位,为构建短肽疫苗奠定基础。方法采用合成肽Sj22.6-P4、无关肽（对照）及PBS免疫C57BL/6小鼠2次（间隔7 d）,末次免疫后7～10 d取脾分离单个核细胞,用合成肽Sj22.6-P4、无关肽及PBS刺激培养,3H-TdR掺入法检测淋巴细胞的增殖效果,酶联免疫吸附试验（ELISA）检测其细胞培养上清中IFNγ-、IL-4及IL-2水平。运用流式细胞技术三色标记法检测经合成肽Sj22.6-P4、无关肽及PBS免疫2次的C57BL/6小鼠脾淋巴细胞内的Th1、Th2细胞因子。结果合成肽Sj22.6-P4可刺激经该抗原肽免疫2次的C57BL/6小鼠淋巴细胞增殖,与PBS组相比,增殖指数（SI）均〉2。与无关肽对照组相比,细胞培养上清中IL-2、IFN-γ分泌水平增高,其中IL-2分泌水平差异有统计学意义（P〈0.05）,IFN-γ差异无统计学意义（P〉0.05）,而IL-4分泌水平明显降低（P〈0.05）。合成肽Sj22.6-P4免疫组小鼠脾脏CD4＋T细胞中分泌IFN-γ细胞的百分比显著增高,分泌IL-4细胞的百分比显著降低（P均〈0.05）。结论合成肽Sj22.6-P4是C57BL/6小鼠特异的Th1型表位。     

Cytokines and antibody responses during Trypanosoma congolense infections in two inbred mouse strains that differ in resistance

We studied IL-4, IL-10 and IFN-gamma secretion by splenocytes and the plasma levels of different isotypes of antibodies against various antigens of Trypanosoma congolense in highly susceptible BALB/c and relatively resistant C57BL/6 mice during the early course of infection with T. congolense. The patterns of appearance of cytokine spotforming cells in the spleens were essentially similar in the two mouse strains although higher numbers were detected in the spleens of BALB/c than C57BL/6 mice on some days post-infection. However, the amount of IL-4, IL-10 and IFN-gamma secreted into the culture fluids was dramatically different. From day 4 forward, splenocytes from BALB/c mice secreted very high levels of these cytokines. In contrast, splenocytes from infected C57BL/6 mice did not secrete detectable levels of IL-4 throughout the period tested. The secretion of IL-10 and IFN-gamma by C57BL/6 splenocytes only became appreciable on day 6 and was down-regulated by day 8, when the first wave of parasitaemia was being controlled. At days 6-8, splenocytes from infected C57BL/6 mice secreted two-fold higher amounts of IL-12 p40 than those from BALB/c mice. Infected BALB/c mice mounted an earlier IgM antibody response to variant surface glycoprotein (VSG), formalin-fixed T. congolense and whole T. congolense lysates than did infected C57BL/6 mice. However, they failed to make any detectable IgG3 and IgG2a antibody responses to these antigens whereas infected C57BL/6 mice made strong IgG3 and IgG2a responses. We speculate that enhanced resistance against T. congolense infections in mice may be mediated by IL-12 dependent synthesis of IgG2 antibodies to VSG and possibly also common trypanosomal antigens.     

CD4+ and/or gammadelta+ T cells in the liver spontaneously produce IL-4 in vitro during the early phase of Leishmania major infection in susceptible BALB/c mice.

Numerous studies on the cytokine production profile in Leishmania major infected susceptible and resistant mice have been carried out to elucidate the mechanisms of healing or non-healing of this infection. However, many methods may have failed to detect the actual cytokine production in the inflammatory foci. To overcome this problems, the ELISPOT assay was used to examine the spontaneous production of IL-4 and IFN-gamma in vitro by mononuclear cells from the spleen, lymph nodes and liver in L. major-infected susceptible BALB/c and resistant C57BL/6 mice. None of these mononuclear cells spontaneously produced IFN-gamma in either mouse strains in vitro in the absence of the corresponding antigen(s). However, liver mononuclear cells from infected BALB/c mice spontaneously produced IL-4 in vitro in as early as 2 weeks after the infection, but this was not observed in C57BL/6 mice. The IL-4 producing liver lymphocytes consisted of CD4+ and/or gammadelta+ T cells and uncharacterized cells. These results suggest that liver lymphocytes play some role in the establishment of Th2 prevalence in susceptible BALB/c mice, based on the importance of IL.4 production in the early phase of L. major infection in establishing Th2 dominance in this parasite susceptible mouse.     

Mice deficient in Th1- and Th2-type cytokines develop distinct forms of hapten-induced colitis

BACKGROUND & AIMS: Most experimental models for inflammatory bowel disease in mice are associated with production of interferon (IFN)-gamma and other proinflammatory cytokines. We hypothesized that T-helper 2 (Th2)-type cells could also contribute to the colitis and cause inflammation different than that mediated by Th1-type cells. METHODS: Trinitrobenzene sulfonic acid (TNBS)-induced colitis in C57BL/6 background mice genetically deficient in interleukin (IL)-12 p40 (IL-12(-/-)), IFN-gamma (IFN-gamma(-/-)), or IL-4 (IL-4(-/-)) was examined in comparison with control mice (C57BL/6(+/+)). RESULTS: C57BL/6(+/+), IFN-gamma(-/-), and IL-12(-/-) mice developed patterns of colitis characterized by distortion of crypts, loss of goblet cells, and mononuclear cell infiltration with fibrosis of the mucosal layer. IL-4(-/-) mice had greater mortality than other groups because of penetrating ulcers; however, survivors developed milder lesions that were limited to focal acute ulceration. Colonic CD4(+) T cells from normal, IFN-gamma(-/-), or IL-12(-/- )mice produced both IL-4 and IL-5. CONCLUSIONS: In TNBS colitis, Th1-like cytokine responses induce fatal, acute, transmural, and focal types of lesions, whereas Th2-like cytokine responses play a significant role in the diffuse atrophic changes in crypts and the mucosal layer that occur in the late stages of this disease.     

Mechanisms of resistance/susceptibility to murine encephalitozoonosis

Mechanisms of resistance/susceptibility to the obligate intracellular protozoan Encephalitozoon cuniculi were studied in resistant BALB/c and susceptible C57BL/6 mice. Three immunological functions were examined: the production of lymphokine(s) (LK) by T-lymphocytes, the proliferative response of spleen cells to parasite spore fragments, and the ability of splenic and thioglycollate-induced peritoneal macrophages to act as accessory cells in antigen-induced T-cell proliferation. The two strains showed differences in the time required for LK production in vitro but not in their ability to generate LK. Spore fragment-induced lymphoblastogenesis was found in spleen cells of infected BALB/c and C57BL/6 mice. There was no difference between the two strains in dose response and time of maximal response, but the magnitude of maximal response was significantly less in C57BL/6 mice. Indomethacin was found to augment the lymphoproliferative response of C57BL/6 but not BALB/c mice, suggesting that prostaglandin production may be involved in immunosuppression in C57BL/6 mice. C57BL/6 mice required more splenic adherent cells to achieve the same proliferative response as found in BALB/c mice. The ability of thioglycollate-induced peritoneal macrophages to act as accessory cells in antigen-induced T-cell proliferation was less in C57BL/6 mice than in BALB/c mice. Thus, it appeared that the relative susceptibility of C57BL/6 mice to encephalitozoonosis may be due to defective accessory cell function of splenic and peritoneal macrophages, depressed lymphoproliferation against spore fragments (possibly due to prostaglandin-mediated suppression) and a delay in LK production. There was no significant difference between the survival times of BALB/c-nu and C57BL/6-nu mice, suggesting that non-immune mediated resistance did not play a role in determining resistance/susceptibility.     

Fasciola hepatica infection downregulates Th1 responses in mice

Immune responses induced with helminth parasites have been extensively studied, but there is limited information on those to Fasciola hepatica, especially on the subtype of T cell induced with this parasite. We investigated the local and systemic T cell responses of different strains of mice following oral infection with doses of metacercariae from F. hepatica. Spleen cells from BALB/c and 129Sv/Ev mice given a low-dose (5 metacercariae) infection exhibited a Th2 response, producing high levels of the cytokines IL-4 and IL-5, and low levels of IFN-gamma and IL-2. In contrast, C57BL/6 mice showed a mixed Th1/Th2 response. A more marked polarization to a Th2 response was observed in BALB/c, 129Sv/Ev exposed to a high-dose (15 metacercariae) infection and the C57BL/6 mice also exhibited a clear Th2 response. IL-4 defective (IL-4-/-) C57BL/6 mice infected with 5 metacercariae produced less IFN-gamma and more IL-5 compared to their wild-type C57BL/6 counterparts, suggesting that IL-4 is important in establishing the Th2 type response in murine fasciolosis. However, the secretion of IFN-gamma and IL-2 was completely suppressed in the high-dose infection and this was also observed in IL-4-/- mice. Thus, liver flukes may secrete molecules that downregulate Th1 responses. T cell responses in the mesenteric (MLN) and hepatic lymph nodes (HLN) were also examined since newly excysted juveniles infect through the intestinal wall of their host before migrating to the hepatic tissue. Cells from both MLN and HLN secreted higher levels of IL-4 and IL-5 compared to spleen cells. We also observed a difference in cytokine profiles secreted by the MLN and HLN, which may reflect responses to antigens liberated by newly excysted juveniles and hepatic stage parasites, respectively.     

Immunoregulation in experimental murine Trypanosoma congolense infection: anti-IL-10 antibodies reverse trypanosome-mediated suppression of lymphocyte proliferation in vitro and moderately prolong the lifespan of genetically susceptible BALB/c mice

We infected highly susceptible BALB/c and relatively resistant C57BL/6 mice with cloned Trypanosoma congolense and followed the effects of these infections on the circulating parasite numbers, mouse mortality and cytokine expression. C57BL/6 mice controlled their parasitaemia and survived for up to 163 ± 12 days, while BALB/c mice could not control their parasitaemia and succumbed to the infection within 8.4 ± 0.5 days. Susceptible BALB/c mice had dramatically higher plasma levels of IL-10 than the resistant C57BL/6 mice from day 7 forward. This was preceded by an earlier and higher level induction of splenic IL-10 messenger RNA (mRNA) expression in the infected BALB/c mice. There was a strong negative correlation between the splenocyte proliferative responses to Concanavalin-A (Con-A) and their production of IL-10 in these infected BALB/c mice. Co-treatment of the Con-A-stimulated spleen cell cultures with monoclonal anti-IL-10 antibodies, but not isotype-matched control antibodies, could completely reverse this suppression of the splenocyte proliferative response. Finally, in three experiments, anti-IL-10 antibody treatment in vivo reduced the peak circulating parasitaemia of infected BALB/c mice by 43% and increased their median survival periods by 38% relative to isotype-matched control antibody-treated mice .     

Periostin Contributes to the Pathogenesis of Atopic Dermatitis by Inducing TSLP Production from Keratinocytes

BackgroundAtopic dermatitis (AD) is a chronic inflammatory skin disease where Th2-type immune responses are dominant. Keratinocytes persistently secrete proinflammatory cytokines and chemokines, amplifying Th2-type responses in AD. We have recently reported that periostin, an extracellular matrix protein induced by Th2 cytokines, plays a critical role in AD. In the present study, we have further investigated the characteristics of our allergen-induced AD model mice and the role of periostin in the pathogenesis of AD.MethodsThe ears of C57BL/6 mice, BALB/c mice, and Rag-2^?/? γc^?/? mice (BALB/c background) were epicutaneously sensitized repeatedly with HDM. Mice were analyzed after the final sensitization. To examine the direct role of periostin, we reconstituted skin in vitro by coculture of keratinocytes with wild-type or periostin-deficient fibroblasts.ResultsEpicutaneous sensitization with HDM induced AD-like phenotypes and accumulation of periostin in dermis in C57BL/6 mice but not in Rag-2^?/? γc^?/? mice. In vitro organotypic coculture systems revealed that periostin promoted survival and proliferation of keratinocytes and directly induced production of thymic stromal lymphopoietin (TSLP).ConclusionsOur results suggest that periostin exacerbates the pathogenesis of AD through TSLP production from keratinocytes.     

Prevention of lethal acute graft-versus-host disease in mice by oral administration of T helper 1 inhibitor, TAK-603

Acute graft-versus-host diseases (GVHD) is a major cause of morbidity and mortality in patients undergoing allogeneic bone marrow transplantation (BMT). T helper 1 (Th1)-type cytokines such as interferon-gamma or tumor necrosis factor-alpha have been implicated in the pathogenesis of acute GVHD. TAK-603 is a new quinoline derivative, which is now in clinical trials for use as a disease-modifying antirheumatic drug. In preclinical studies, it inhibited delayed-type hypersensitivity, but not Arthus-type reaction, in mice, and selectively suppressed Th1 cytokine production. Thus, the present study was designed to investigate whether the Th1 inhibitor (TAK-603) ameliorates lethal acute GVHD in a mouse model. Administration of TAK-603 into BALB/c mice given 10 Gy total body irradiation followed by transplantation of bone marrow and spleen cells from C57BL/6 mice markedly reduced the mortality in association with minimal signs of GVHD pathology in the liver, intestine, and skin. TAK-603 reduced not only the production of Th1-type cytokines, but also the proportion of Th1 cells in CD4(+) helper T cells in this GVHD mouse model. These results suggest that TAK-603 could be a potent therapeutic agent for acute lethal GVHD.     

Apoptosis in the regulation of immune response in mice infected with Heligmosomoides polygyrus

An unbalanced Th1 and Th2 cell subsets response was proposed as the main downregulating mechanisms operating in mice infected with H. polygyrus. During worm infections nonspecific inflammatory and specific immune reactions which might be regulated by apoptosis, coordinate the host protective response. The intensity of apoptosis and proliferation of lymphocytes, the concentration of Th1 and Th2 related cytokines were measured in BALB/c and C57BL6 mice on day 3, 6, 12, 24, 30 after infection with H. polygyrus. Mesenteric lymph nodes (MLN) and popliteal lymph nodes (PLN) lymphocytes underwent an apoptosis, with a different kinetics to the proliferation. Interleukine 5 and IL-6 concentrations increased on time when apoptosis was reduced. No changes in the level of IL-12 were related to intensity of proliferation or apoptosis in both examined strains of mice.     

慢性日本血吸虫感染C57BL／6小鼠体内Th1／Th2细胞凋亡的检测

目的 观察日本血吸虫感染晚期C57BL／6小鼠体内Th1、Th2细胞凋亡水平的变化。方法运用流式细胞技术，采用表面分子、胞内因子同时染色的三色标记和间接标记的方法，对日本血吸虫感染13周的C57BL／6小鼠脾脏、淋巴结中的Th1、Th2细胞的凋亡水平进行观察。结果日本血吸虫感染晚期C57BL／6小鼠与正常小鼠相比，Th1、Th2细胞凋亡均显著增加，但Th1细胞凋亡较多而Th2细胞凋亡较少。此阶段Th1细胞凋亡比Th2细胞更加易感。结论Th1、Th2细胞凋亡易感性的不同可能是导致血吸虫感染晚期Th2极化的原因之一，此为血吸虫感染过程中Th极化研究提供了新的证据。     

Parasitic load and histopathology of cutaneous lesions,lymph node,spleen, and liver from BALB/c and C57BL/6 mice infected with Leishmania mexicana

The course of infection, parasitic loads, and histopathology of cutaneous lesions, draining lymph node, spleen, and liver were compared in BALB/c and C57BL/6 mice over a period of 34 weeks after inoculation in footpad with promastigotes of a Leishmania mexicana reference strain. The results show that the primary footpad lesions first present a 12-week phase that develops similarly in both strains of mice. Thereafter, a cutaneous and visceral dissemination of L. mexicana parasites occurs in BALB/c mice; the latter experience an extensive breakdown of the lymphoid organ microarchitecture, whereas C57BL/6 mice succeed in eliminating the parasite infection from the lymph nodes but not from the primary cutaneous lesion, which does not heal. These results highlight marked differences between responses of key anatomical compartments controlling L. mexicana infection in BALB/c and C57BL/6 mice.     

Inducible nitric oxide synthase and arginase expression in heart tissue during acute Trypanosoma cruzi infection in mice: arginase I is expressed in infiltrating CD68+ macrophages

In Chagas disease, which is caused by Trypanosoma cruzi, macrophages and cardiomyocytes are the main targets of infection. Classical activation of macrophages during infection is protective, whereas alternative activation of macrophages is involved in the survival of host cells and parasites. We studied the expression of inducible nitric oxide synthase (iNOS) and arginase as markers of classical and alternative activation, respectively, in heart tissue during in vivo infection of BALB/c and C57BL/6 mice. We found that expression of arginase I and II, as well as that of ornithine decarboxylase, was much higher in BALB/c mice than in C57BL/6 mice and that it was associated with the parasite burden in heart tissue. iNOS and arginase II were expressed by cardiomyocytes. Interestingly, heart-infiltrated CD68+ macrophages were the major cell type expressing arginase I. T helper (Th) 1 and Th2 cytokines were expressed in heart tissue in both infected mouse strains; however, at the peak of parasite infection, the balance between Th1 and Th2 predominantly favored Th1 in C57BL/6 mice and Th2 in BALB/c mice. The results of the present study suggest that Th2 cytokines induce arginase expression, which may influence host and parasite cell survival but which might also down-regulate the counterproductive effects triggered by iNOS in the heart during infection.