IFN-γ和IL-4抗卡氏肺孢子虫感染作用的研究

目的研究细胞因子IFN-γ和IL-4的抗卡氏肺孢子虫感染作用.方法分别用IFN-γ或IL-4基因敲除的C57BL/6小鼠(各15只作为动物模型)与未经基因敲除的C57BL/6小鼠(15只作感染对照组),以密切接触的方式,使小鼠自然感染卡氏肺孢子虫;同时设非感染组15只小鼠作阴性对照.分别于3、5和7 wk后观察各组小鼠肺内虫体数量、肺部CD4+、CD8+T细胞反应以及血清中卡氏肺孢子虫特异性IgG抗体滴度.分析基因敲除鼠对卡氏肺孢子虫的易感性.结果IFN-γ基因敲除小鼠肺内虫体数量明显高于IL-4基因敲除小鼠(P＜0.05)和对照组小鼠,而IL-4基因敲除小鼠肺内虫体数量与对照组无显著性差异(P＞0.05).T细胞亚群分析表明,两种基因敲除小鼠的CD4+和CD8+T细胞反应曲线与感染度呈正相关.而IgG抗体滴度,3组接触感染鼠均逐渐呈不同程度上升.结论IFN-γ在小鼠抗卡氏肺孢子虫中起重要作用,但缺少IL-4基因的小鼠对肺孢子虫感染的影响不明显.     

IFN-γ和IL-4抗卡氏肺孢子虫感染作用的研究

目的　研究细胞因子IFN γ和IL 4的抗卡氏肺孢子虫感染作用。　方法　分别用IFN γ或IL 4基因敲除的C5 7BL 6小鼠 (各 15只作为动物模型 )与未经基因敲除的C5 7BL 6小鼠 (15只作感染对照组 ) ,以密切接触的方式 ,使小鼠自然感染卡氏肺孢子虫 ;同时设非感染组 15只小鼠作阴性对照。分别于 3、5和 7wk后观察各组小鼠肺内虫体数量、肺部CD4+ 、CD8+ T细胞反应以及血清中卡氏肺孢子虫特异性IgG抗体滴度。分析基因敲除鼠对卡氏肺孢子虫的易感性。　结果　IFN γ基因敲除小鼠肺内虫体数量明显高于IL 4基因敲除小鼠 (P <0 .0 5 )和对照组小鼠 ,而IL 4基因敲除小鼠肺内虫体数量与对照组无显著性差异 (P >0 .0 5 )。T细胞亚群分析表明 ,两种基因敲除小鼠的CD4+ 和CD8+ T细胞反应曲线与感染度呈正相关。而IgG抗体滴度 ,3组接触感染鼠均逐渐呈不同程度上升。　 结论　IFN γ在小鼠抗卡氏肺孢子虫中起重要作用 ,但缺少IL 4基因的小鼠对肺孢子虫感染的影响不明显。     

疟原虫全虫疫苗长效保护性下降机制初探

目的探讨疟疾红外期全虫疫苗免疫保护性随时间逐渐降低的机制。方法取C57BL/6及BALB/c小鼠,经尾静脉分别接种10 000或50 000约氏疟原虫(P.yoelii)17XNL子孢子,3h后给予氯喹控制红内期感染的发生。一部分小鼠于接种后30、90、180d用10 000同种疟原虫子孢子进行攻击检查保护性;另一部分在相同时间点取血,分离淋巴细胞,进行流式抗体染色,检测免疫保护性及其与肝脏淋巴细胞表型间的相互关系。结果疟原虫全虫抗原免疫后30d两种小鼠均可产生100%的免疫保护;免疫后90d,C57BL/6保护性开始下降,180d时保护性将至40%,而BALB/c小鼠保护性无明显变化。C57BL/6小鼠肝脏CD8~+T_(EM)细胞PD-1的表达在免疫后180d显著上升(t=7.369,P0.01),BALB/c小鼠无明显变化(t=1.368,P0.05)。C57BL/6小鼠肝脏CD8~+T_(EM)细胞PD-1的表达免疫后随时间增加而升高,其中免疫后180d较90d时上升趋势更显著(t=6.175,P0.01)。结论在C57BL/6小鼠,疟原虫红外期全虫疫苗免疫保护性随免疫时间延长逐渐降低与肝脏CD8~+T细胞PD-1表达增高有关。     

抗日本血吸虫重组蛋白20.8kDa抗原单克隆抗体的建株

以日本血吸虫重组蛋白 2 0 .8k Da抗原免疫 BAL B/ c小鼠 ,制备单克隆抗体。每鼠注入蛋白 10 0μg,共免疫 3次 ,第1次加福氏完全佐剂 ,第 2、 3次加福氏不完全佐剂 ,间隔 3wk。融合前 ,于免疫的 BAL B/ c小鼠尾静脉注射 5 0 μg血吸虫重组蛋白 2 0 .8k Da抗原 ,4 d后取脾脏与骨髓瘤细胞 SP2 / O融合 ,11d后检测 ,融合率为 13.5 4 % (2 6 / 192 )。EL ISA检测培养上清 ,筛选阳性孔 ,经 3次克隆 ,获得 6株阳性杂交瘤细胞株。将这 6株细胞上清浓缩 10倍 ,用琼脂双扩散法测得免疫球蛋白亚类为 Ig G1 4株 ,Ig M2株。将 6株细胞扩增后注…     

CD4~+CD25~+调节性T细胞对啮齿类疟原虫感染过程及结局的影响

目的探讨CD4+CD25+调节性T细胞数量在约氏疟原虫(致死型)和夏氏疟原虫混合感染小鼠免疫应答中的动态变化。方法DBA/2和BALB/c小鼠分别经腹腔注射致死型约氏疟原虫(P.y17XL)、夏氏疟原虫(P.cAS)和P.y17XL+P.cAS(1∶1)混合感染的红细胞,计数红细胞感染率;采用流式细胞术动态检测脾细胞中Tregs细胞数量的变化。结果P.y17XL+P.cAS感染的DBA/2小鼠于感染后18d自愈;而BALB/c小鼠于感染过程中虽然出现死亡(8d),但与P.y17XL感染小鼠(5d)相比,死亡时间明显延迟;P.y17XL和P.y17XL+P.cAS感染的DBA/2鼠于感染后第5d CD4+CD25+调节性T细胞数量均达峰值,随后缓慢下降,相比P.cAS感染的DBA/2鼠于感染后第10d达峰值,是其它两种同天感染鼠的3倍和2倍,且小鼠全部死亡;而P.y17XL和P.y17XL+P.cAS感染的BALB/c小鼠CD4+CD25+调节性T细胞数量于感染后均迅速升高,分别于感染后第5d和第8d达30%左右,小鼠全部死亡,相比P.cAS感染的BALB/c小鼠CD4+CD25+调节性T细胞数量于感染后缓慢升高,于感染后第5d达14%,随后开始下降。结论①P.y17XL+P.cAS混合感染DBA/2鼠后CD4+CD25+调节性T细胞数量的动态变化与P.y17XL单独感染表现出完全相同的模式;BALB/c鼠:CD4+CD25+调节性T细胞数量的动态变化与P.y17XL单独感染也表现出完全相同的模式,但变化的时间明显被滞后;②CD4+CD25+调节性T细胞的异常升高与感染结局密切相关。     

肺间质纤维化小鼠肺内T细胞γ-干扰素和转化生长因子β1的表达

目的 探讨肺组织内T细胞及其转化生长因子β1(TGF-β1)/γ-干扰素(IFN-γ)表达与肺间质纤维化的关系.方法 C57BL/6小鼠30只,随机分为5组,即正常对照组和博莱霉素1、2、3、4周组.采用气管内注射博莱霉素(5 mg/kg)建立纤维化模型,分别于造模后1、2、3、4周断头处死,留取各组小鼠肺组织,观察肺泡炎和肺纤维化程度,流式细胞仪在单个细胞水平检测CD4+、CD8+、CD3+/CD8-/IFN-γ+和CD3+/CD8-/TGF-β1+细胞的频率.结果 博莱霉素组小鼠出现明显纤维化;与正常对照组相比,博莱霉素组肺组织CD4+明显增多,CD8+显著降低(P值均<0.01);博莱霉素组肺组织CD4+T细胞来源IFN-γ水平低于正常对照组,而CD4+T细胞来源TGF-β1水平显著增高于正常对照组(P值均<0.01);CD4+TGF-β1+/CD4+IFN-γ+比值进行性增高,与肺纤维化评分呈正相关(r=0.683,P<0.01).结论 CD4+T细胞来源IFN-γ与TGF-β1分别下调与上调,参与肺纤维化.     

多房棘球蚴感染对小鼠肝脾淋巴细胞及其亚群的影响

目的探讨多房棘球蚴感染对C57BL/6小鼠肝和脾淋巴细胞及其亚群的影响。方法 32只C57BL/6小鼠随机分为4组,每组8只,对照组、低数量组(50个原头节/鼠)、中数量组(500个原头节/鼠)、高数量组(2 000个原头节/鼠),实验组取200μl含不同数量多房棘球蚴原头节的混悬液,采用门静脉注射法建立多房棘球蚴感染小鼠模型,对照组注射等量生理盐水。感染后4周,每组各取4只小鼠,取肝脏组织,常规Masson染色,观察病理变化。剩余4只小鼠取肝脏和脾脏,制备肝、脾细胞悬液,流式细胞术检测肝、脾CD3^+T细胞、B细胞、NK细胞、NKT细胞、CD4^+T细胞、CD8^+T细胞、CD4^+CD69^+T细胞、CD8^+CD69^+T细胞绝对数以及初始型CD4^+T (CD4^+Tn)细胞、效应记忆性CD4^+T (CD4^+Tem)细胞、初始型CD8^+T (CD8^+Tn)细胞、效应记忆性CD8^+T(CD8^+Tem)细胞和中心记忆性CD8^+T(CD8^+Tcm)细胞比例的变化。检测数据采用Flow-Jo软件分析,并做流式图。采用Graphad Prism 7.0软件进行作图和统计学分析。结果感染后4周,对照组小鼠肝无明显变化,低、中数量组小鼠肝组织出现急性炎症反应减弱,部分病灶炎性反应逐渐转变为纤维化修复,形成小肉芽肿结节,呈点状或灶状坏死。高数量组小鼠肝内出现小囊泡,可见生发层结构,周围大量炎性细胞浸润。小鼠肝CD3^+T细胞绝对数高、中、低数量组和对照组分别为(4.10±0.04)×10^5、(3.81±0.14)×10^5、(3.02±0.12)×10^5、(2.98±0.03)×10^5,高数量组高于其他3组(P<0.05或0.01)。小鼠脾CD3^+T细胞绝对数高、中、低数量组和对照组分别为(16.01±0.40)×10^5、(11.03±1.21)×10^5、(10.10±1.01)×10^5、(9.71±0.90)×10^5,高数量组高于其他3组(P<0.01)。小鼠肝CD4^+T、CD8^+T细胞和脾B细胞、CD8^+T绝对数高数量组高于其他3组(P<0.05或0.01)。小鼠肝CD4^+CD69^+T细胞绝对数高、中、低数量组和对照组分别为(3.23±0.10)×10^4、(1.98±0.11)×10^4、(1.51±0.26)×10^4、(1.19±0.21)×10^4,高数量组高于其他组(P<0.05)。小鼠脾CD4^+CD69^+T细胞绝对数高、中、低数量组和对照组分别为(10.10±0.41)×10^4、(8.91±0.80)×10^4、(8.20±0.41)×10^4、(6.81±0.50)×10^4,高数量组高于对照组(P<0.01)。肝、脾CD8^+CD69^+T细胞绝对数高数量组高于其他3组(P<0.05或0.01)。小鼠肝CD4^+Tn细胞比例高、中、低数量组和对照组分别为(15.52±1.51)%、(19.3±2.09)%、(20.66±1.28)%、(23.62±2.84)%,对照组高于其他组(P<0.05或0.01)。肝、脾CD8^+Tn细胞比例对照组高于其他组(P<0.05或0.01)。肝、脾CD8^+Tcm细胞比例高数量组高于对照组(P<0.05)。结论高数量多房棘球蚴感染C57BL/6小鼠,肝区域以CD4^+T细胞和CD8^+T细胞募集为主,而脾以B细胞和CD8^+T细胞募集为主。     

日本血吸虫感染小鼠肠系膜淋巴结Th17细胞的免疫应答

目的观察C57BL/6小鼠感染日本血吸虫后肠系膜淋巴结Th17细胞的免疫应答。方法 20只C57BL/6小鼠随机分为感染组和对照组,每组10只,感染组小鼠经腹部皮肤感染日本血吸虫尾蚴,每鼠(40±5)条。感染后5~6周分离小鼠肠系膜淋巴结的淋巴细胞,分别用抗小鼠CD3单克隆抗体(anti-CD3,1μg/ml)和抗小鼠CD28单克隆抗体(anti-CD28,1μg/ml)刺激,培养4 h后收集细胞,RT-PCR检测小鼠肠系膜淋巴结淋巴细胞中白细胞介素17(IL-17)和维甲酸相关孤独受体(ROR-γt)mRNA的转录水平;培养72 h后,ELISA检测细胞培养上清液IL-17和γ干扰素(IFN-γ)的含量。同时用佛波酯(PMA,10 ng/ml)和离子霉素(1μg/ml)刺激淋巴细胞5 h后,胞内细胞因子染色,流式细胞术检测Th17细胞的含量和其他细胞因子的产生。结果 ELISA检测结果显示,感染小鼠肠系膜淋巴结培养物上清液中IFN-γ[(214.3±62.6)pg/ml]和IL-17[(176.8±62.1)pg/ml]的含量明显高于健康小鼠[(46.7±13.9)和0 pg/ml](P<0.05)。RT-PCR检测结果显示,IL-17和ROR-γt mRNA转录水平也明显高于健康小鼠。感染小鼠肠系膜淋巴细胞CD4+T细胞中,Th17细胞的比例为(0.55±0.03)%,明显高于健康小鼠[(0.16±0.01)%](P<0.05)。在CD4+T细胞中,IL-17+IL-4+细胞占0.06%,IL-17+IFN-γ+和IL-17+IL-5+细胞各占0.02%,IL-17+IL-9+细胞占0.01%,未检测到IL-17+IL-10+和IL-17+Foxp3+细胞。结论日本血吸虫感染C57BL/6小鼠的肠系膜淋巴结能诱导Th17细胞产生。Th17细胞能分泌IL-4,及少量的IFN-γ、IL-5和IL-9,不分泌IL-10,也不表达Foxp3。     

日本血吸虫SjC21.7核酸疫苗诱导小鼠保护性免疫作用的研究

目的　研究日本血吸虫中国大陆株 2 1.7k Da膜蛋白分子 (Sj C2 1.7)核酸疫苗对 BAL B/ c小鼠的免疫保护性作用。　方法　采用 PCR方法扩增出特异性 Sj C2 1.7基因的开放阅读框序列 ,在其起始密码子处引入 Kozark序列。将目的基因片段亚克隆到真核表达质粒 pc DNA3.1中 ,构建重组真核表达质粒 Sj C2 1.7- pc DNA3.1。 4 8只 BAL B/ c小鼠分为对照组、实验组和加强组。对照组小鼠的股四头肌注射接种 pc DNA3.1,实验组同法注射重组质粒 Sj C2 1.7- pc D-NA3.1,加强组除注射重组质粒 Sj C2 1.7- pc DNA3.1外 ,同时注射重组质粒 P35 - pc DNA3.1及 P4 0 - pc DNA。每隔 2 wk免疫 1次 ,共免疫 3次。第 3次免疫后第 30天 ,每只鼠感染 4 5± 1条尾蚴 ,4 5 d后剖杀计数各组小鼠成虫数及肝卵数。通过 EL ISA和免疫组化分析观察小鼠免疫学特征的变化。　结果　免疫组化分析显示 ,实验组小鼠股四头肌局部组织有特异性抗原蛋白表达。EL ISA分析表明 ,免疫后实验组和加强组有部分小鼠出现特异性 Ig G抗体。与对照组比较 ,实验组减虫率及减卵率分别为 2 9.9%及 13.8% ,加强组分别为 31.9%及 2 8.0 %。加强组减卵率显著高于实验组(P<0 .0 5 )。　结论　 Sj C2 1.7核酸疫苗能诱导 BAL B/ c小鼠产生一定水平的抗血吸虫感染     

真核表达载体pcDNA3-CTLA4Ig转染小鼠对移植胰岛功能的影响

目的:探讨真核表达载体pcDNA3-CTLA4Ig转染受体小鼠肌细胞后对胰岛移植后排斥反应的影响.方法:受体C57BL/6小鼠随机分为对照组、空白转染组和实验组(转染pcDNA3-CTLA4Ig).Western blot检测受体小鼠血清CTLA4-Ig表达,观察移植物存活时间,术后7 d取受体肾脏做HE染色及胰岛素免疫组化染色,采用微量全血~3H-胸腺嘧啶掺入法检测单个核细胞在刀豆蛋白A刺激下的增殖程度,流式细胞仪检测外周血T细胞亚群表达情况.结果:受体小鼠转染5 d后,Western blot检测到血清内有CTLA4Ig表达,转染效率为27.50%;实验组小鼠血糖维持正常时间明显延长(P<0.05):术后7 d,转染组单个核细胞在刀豆蛋白刺激下的增殖程度明显降低(P<0.05),CD4~ 、CD8~ T淋巴细胞表达与对照组和空白转染组相比有显著差异差异(CD4~ :14.38%±0.84% vs 20.56%±0.68%,21.04%±1.14%,P<0.05:CD8~ :14.77%±0.92% vs 24.63%±1.30%,23.84%±1.21%,P<0.05),小鼠肾被膜下胰岛素免疫组化染色强度明显增高.结论:利用脂质体法可将pcDNA3-CTLA4Ig转染到活体小鼠肌细胞内并在小鼠体内表达CTLA4Ig,从而阻断B7/CD28共刺激信号途径,抑制胰岛移植术后排斥反应.     

Leishmania infantum released proteins specifically regulate cytokine expression and production patterns by CD4+ and CD8+ T cells

Specific immune responses by CD4+ and CD8+ T cells, from two infected mice strains (BALB/c and C57BL/6), induced by High, Inter and Low protein fractions released by Leishmania infantum, were assessed through the evaluation of IL-12, IFN-gamma and IL-10 mRNA by real-time PCR and respective protein production by ELISA. During infection establishment, High and Inter fractions directed both mice strains T cells subsets to increase the production of IFN-gamma, associated to IL-12 release. Later on, parasite replication augmented in BALB/c and stabilised in C57BL/6 mice. Inter fraction induced CD4+ T cells to maintain IFN-gamma production, with the simultaneous release of IL-12 by both cell subsets in BALB/c mice and by CD8+ T cells in C57BL/6 mice. These observations suggested a prophylactic potential for Inter fraction which was able to induce Th1 response with IL-12 involvement, required for the maintenance of memory cells, in mice strains with different parasitic evolution.     

Influence of free radicals on Trichinella spiralis infection in mice

The aim of the study was to examine the influence of free radicals: nitric oxide (NO), hydrogen peroxide (H202) and superoxide anion (O2-) on Trichinella spiralis infection in mice. The studies were performed on two strains of mice: C57BL/6 and BALB/c, which differ in immunological response to T. spiralis infection. Also the influence of AG--inhibitor of inducible nitric oxide synthase (iNOS) administered in the first days after T. spiralis infection (1-5 dpi) on the cytotoxic immune response and on the number of adult parasites as well as the influence of AG administered at the beginning of muscle phase of the T. spiralis infection (16-29 dpi) on the cytotoxic immune response and the number of muscle larvae was studied. Activation of macrophages can cause pathology. Contact of macrophages with antigens stimulates these cells to produce, among others, highly reactive inorganic compounds. There are free radicals: NO, H2O2 and O2-. NO, O2-, and their metabolites are highly toxic for most pathogens, including parasites. However, little is known about their role in the defense against T. spiralis infection. The performed studies have proved, that free radicals play role in the host immune response during both intestinal and muscle phase of T. spiralis infection in mice. In the intestinal phase of the T. spiralis infection cytotoxic immune response is activated in mice peritoneal cavity and in the muscle phase, the local immune response activated in the neighborhood of larvae in muscles appeared as the higher level of free radicals in blood and urine. Administration of AG between 1-5 dpi causes opposite reactions in two different strains of mice. In BALB/c mice AG causes fast expulsion of adult T. spiralis from the intestine but in C57BL/6 mice the expulsion of parasites is slower after AG. However, there are no differences between two strains of mice after treatment with AG between 16 and 29 dpi. AG causes diminution of larvae in muscles of both BALB/c and C57BL/6 mice. Inflammatory response in peritoneal cavity is observed later during the infection in "low responders" (C57BL/6) mice in comparison with "high responders" (BALB/c) mice. Thl like mice (C57BL/6) react stronger to AG treatment than Th2 like mice (BALB/c). It occurs as changes and fluctuations in free radicals levels and the number of peritoneal cells after AG treatment in C57BL/6 mice.Weak or no reaction on AG injections in BALB/c mice is responsible for more stabile and more sufficient defense response of the host to T. spiralis infection.     

PRU株弓形虫包囊感染小鼠模型的建立

目的建立一个合理、经济的弓形虫包囊小鼠感染模型,为弓形虫的相关研究提供参考。方法 20个PRU株弓形虫包囊分别感染C57BL/6J、ICR、KM或BALB/c四个品系雌性小鼠10只,感染后42d,统计小鼠存活率、脑组织包囊数和包囊直径。结果 KM小鼠存活率100%(10/10),ICR小鼠存活率70%(7/10),C57BL/6J存活率10%(1/10),BALB/c全部死亡(0/10);ICR小鼠包囊数和包囊直径与KM小鼠相比具有显著性差异(P0.01):ICR鼠脑组织包囊数为1385.71±378.555,直径为4.044±0.187μm;而KM鼠脑组织包囊数为290.00±129.743,直径为3.557±0.271μm。结论与其他3个品系小鼠相比,ICR小鼠对PRU株弓形虫包囊的抗性较强,可以作为弓形虫包囊感染模型。     

Regulation of Graves' hyperthyroidism with naturally occurring CD4+CD25+ regulatory T cells in a mouse model

Graves' hyperthyroidism can be efficiently induced in susceptible mouse strains by repeated immunization with recombinant adenovirus coding the TSH receptor (TSHR). This study was designed to evaluate the role(s) played by naturally occurring CD4(+)CD25(+) regulatory T cells in the development of Graves' hyperthyroidism in resistant C57BL/6 and susceptible BALB/c mice. Depletion of CD4(+)CD25(+) T cells rendered some C57BL/6 mice susceptible to induction of hyperthyroidism. Thus, hyperthyroidism developed in 30% of the CD4(+)CD25(+) T cell-depleted C57BL/6 mice immunized with adenovirus expressing the TSHR A-subunit (AdTSHR289) vs. 0% of those immunized with AdTSHR289 alone. This immunological manipulation also enhanced disease severity in susceptible BALB/c mice, as reflected by a significant increase in mean T(4) levels by CD4(+)CD25(+) T cell depletion. The immunoenhancing effect of CD4(+)CD25(+) T cell depletion appears to be attributable to an increase in thyroid-stimulating antibody production and/or a decrease in thyroid-blocking antibody synthesis, but not immune deviation to either T helper 1 or 2 cells. Interestingly, unlike BALB/c mice, some hyperthyroid C57BL/6 mice showed some intrathyroidal lymphocytic infiltration with follicular destruction. These results indicate that CD4(+)CD25(+) T cells play a role in disease susceptibility and severity in adenovirus-TSHR-induced Graves' hyperthyroidism. Overall, the imbalance between effector and regulatory T cells appears to be crucial in the pathogenesis of Graves' disease.     

调节性T细胞在不同品系小鼠心脏移植后的变化及意义

目的探讨不同品系小鼠颈部心脏移植后调节性T细胞的变化及意义。方法建立小鼠颈部心脏异位移植模型,实验分2组,受体小鼠均为C57BL／6,供体分别为BALB／c和C57BL／6小鼠。比较两组供心存活时间、排斥反应程度,流式细胞仪测定CD4＋CD25＋调节性T细胞（Tregs）及CD3＋CD8＋T细胞水平。结果术后第7天,异基因组Tregs水平明显低于同基因组（P〈0．05）,而CD8＋T细胞却明显高于同基因组（P〈0．05）。结论Tregs水平高低与心脏移植后免疫耐受的发生、发展密切相关,可作为心脏移植后免疫耐受的监测指标,对移植物的预后估计和急性排斥反应的早期诊断具有重要的临床意义。     

Mast cells are activated by Leishmania mexicana LPG and regulate the disease outcome depending on the genetic background of the host

The regulatory effect of mast cells on the pathogenesis of leishmaniasis is unclear. We report a comparative analysis of TLR2 membrane expression, TNF-α, IL-10 and MIP-1α production, and granule release of bone marrow-derived mast cells (BMMCs) from susceptible BALB/c and resistant C57BL/6 mice, stimulated in vitro with Leishmania mexicana lipophosphoglycan (LPG). We studied the kinetics of mast cell degranulation and parasite numbers in lesions of both mouse strains infected with L. mexicana . We found that BMMCs of C57BL/6 mice expressed more TLR2 and produced higher levels of both cytokines and MIP-1α, whereas BALB/c BMMCs significantly augmented their granule release. Lesions of BALB/c mice showed higher levels of degranulated mast cells at 3 h of infection, whereas after 3 days of infection, the number of degranulated mast cells in C57BL/6 was higher than in BALB/c lesions. Throughout infection, BALB/c mice harboured more parasites. The regulatory effect of mast cells seems to depend on the genetic background of the host: mast cells of BALB/c mice facilitate disease progression due to an augmented inflammatory response early in the infection, whereas mast cells of C57BL/6 mice produce cytokines that regulate inflammation and maintain an elevated number of immune cells in the lesions, promoting disease control.     

Experimental African trypanosomiasis: lack of effective CD1d-restricted antigen presentation

BALB/c mice are highly susceptible to African trypanosomiasis, whereas C57BL/6 mice are relatively resistant. Other investigators have reported that the synthesis of IgG antibodies to purified membrane form of variant surface glycoprotein (mfVSG) of Trypanosoma brucei is CD1 restricted. In this study, we examine the role of the CD1d/NKT cell pathway in susceptibility and resistance of mice to infection by African trypanosomes. Administration of anti-CD1d antibodies to Trypanosoma congolense-infected BALB/c mice neither affects the parasitemia nor the survival time. Correspondingly, CD1d(-/-) and CD1d(+/+) BALB/c mice infected with T. congolense or T. brucei show no differences in either parasitaemia or survival time. The course of disease in relative resistant C57BL/6 mice infected with T. congolense is also not affected by the absence of CD1d. Parasitaemia, survival time, and plasma levels of IgG2a and IgG3 parasite-specific antibodies in infected CD1d(-/-) C57BL/6 are not different from those of infected CD1d(+/+) C57BL/6 mice. We conclude that CD1d-restricted immune responses do not play an important role in susceptibility/resistance of mice infected with virulent African trypanosomes. We speculate that virulent trypanosomes have an evasion mechanism that prevents the induction of a parasite-specific, CD1d-restricted immune response by the host.     

In vitro activity of CD4+ and CD8+ T lymphocytes from mice immunized with a synthetic malaria peptide.

In previous work, a T-helper epitope was mapped within the circumsporozoite protein of the murine malaria parasite Plasmodium yoelii. A 21-mer synthetic peptide corresponding to this epitope (amino acid positions 59-79; referred to as Py1) induced a specific T-cell proliferation in BALB/c and C57BL/6 mice and provided help for the production of antibodies to peptides from the repetitive region, (Gln-Gly-Pro-Gly-Ala-Pro)n, of the P. yoelii circumsporozoite protein when mice were immunized with the Py1 peptide conjugated to the repetitive peptide. Experiments were then designed to study the in vitro antiparasite efficacy of T cells elicited in vivo by peptide immunization. T-cell activity was evaluated on cultured hepatic stages of P. yoelii. Peptide immunizations led to the preferential activation of CD8+ T cells in BALB/c mice and of both CD4+ and CD8+ T cells in C57BL/6 mice. Parasite elimination was mediated directly by these cells and did not seem to be dependent on lymphokine secretion. These data suggest that peptide-primed CD4+ T cells as well as CD8+ T cells could be cytolytic for the hepatic phase of malaria parasites. The fact that the same peptide could activate different lymphocyte populations, depending on the strain of mouse, highlights the importance of a better understanding of the fine mechanisms behind the immune responses to synthetic peptides being tested for malaria vaccine development.     

Genetic background affects susceptibility in nonfatal pneumococcal bronchopneumonia.

A nonfatal pneumococcal lung infection model was required to investigate immune responses during recovery, and the interaction of other diseases subsequent to infection. A murine model of nonfatal pneumococcal lung infection was developed and the effect of genetic background on susceptibility was determined in BALB/c and C57BL/6 mice. Bacteria colonised the lungs and mice developed mild clinical illness with pathophysiology similar to human bronchopneumonia. Recovery was associated with immune cell influx, which cleared bacteria but induced tissue damage characteristic of pneumococcal bronchopneumonia. After clearance, immune cell populations returned to normal and tissues appeared less inflamed. Although bacterial exposure and clearance were similar, the extent of immune cell influx and tissue damage differed significantly. Larger numbers of neutrophils and lymphocytes entered lung tissue and the affected area was greater in BALB/c compared with C57BL/6 mice. An inflammatory basis for differences was determined with greater levels of phagocytosis and oxidative burst observed in BALB/c mice. C57BL/6 mice cleared the low inoculum with a reduced immune response; however, C57BL/6 mice are more susceptible to larger inocula, which overwhelms the immune system. These different susceptibilities result from a greater inflammatory response in BALB/c compared with C57BL/6 mice.