日本血吸虫感染小鼠肠系膜淋巴结T细胞亚群的变化

目的:观察C57BL/6小鼠感染日本血吸虫(Schistosome japonicum,Sj)4～6周肠系膜淋巴结T细胞亚群的改变。方法:用Sj尾蚴腹贴法建立Sj感染的小鼠模型。4～6周后取肠系膜淋巴结做淋巴细胞计数,使用细胞内细胞因子染色的方法,利用流式细胞仪检测肠系膜淋巴结淋巴细胞中分泌不同细胞因子的T细胞亚群含量的变化。结果:Sj感染C57BL/6小鼠4～6周后,肠系膜淋巴结细胞数量明显增多;流式细胞仪检测发现肠系膜淋巴结中CD4+T细胞中分泌IFN-γ的Th1细胞增多1倍,分泌IL-4和IL-5的Th2细胞增多近20倍,Th1/Th2轴发生偏移;分泌IL-17的Th17细胞也增多近5倍;分泌IFN-γ的CD8+T细胞也增多1倍。结论:日本血吸虫感染C57BL/6小鼠4～6周肠系膜淋巴结细胞增多,并向Th2和Th17型细胞极化。     

日本血吸虫感染小鼠的脾脏CD8+PD-1+T细胞的功能特性

目的研究日本血吸虫感染后小鼠脾脏CD8+PD-1+T细胞含量及功能的变化情况。方法使用日本血吸虫感染5～6周的C57BL/6小鼠,分离脾脏,制备石蜡切片,HE染色,观察组织病变情况;分离淋巴细胞并计数,运用流式细胞术检测CD8+PD-1+T细胞的含量;使用细胞表面染色的方法观察CD8+PD-1+T细胞的CD25、CD69、CXCR5、CD40L的表达变化;经PMA和离子霉素的刺激,使用细胞内细胞因子染色的方法检测IFN-γ、IL-10和IL-12的分泌情况。结果日本血吸虫感染后,小鼠体质量下降(P0.05),而脾脏质量和体积均明显上升(P0.01);脾脏中CD8+PD-1+T细胞的比例和绝对值数目增加(P0.01);感染组CD8+PD-1+T细胞高表达CD69(P0.05),而感染组CD8+PD-1+T细胞CXCR5分子表达显著下降(P0.05);经PMA与离子霉素刺激以后,CD8+PD-1+T细胞IFN-γ分泌增加(P0.05)。结论血吸虫感染5～6周小鼠脾脏中CD8+PD-1+T细胞为一群主要的活化细胞群可大量分泌IFN-γ,在血吸虫感染疾病发挥重要的免疫调节作用。     

胞壁表达Der p2的重组BCG对BALB/c小鼠Th细胞免疫应答的影响

目的：观察接种以膜蛋白形式表达屋尘螨抗原Der p2基因的重组BCG(rBCG)，对BALB／c小鼠Th细胞免疫应答的影响。方法：以生理盐水为对照，分别将rBCG和BCG经腹腔注射接种于6～8wk龄和新生BALB／c小鼠，用ELISA法测定小鼠血清、脾脏T细胞培养上清(STLCS)中IL-4、IFN-γ水平，用双色荧光标记-流式细胞仪法测定脾脏细胞Th细胞亚群。结果：接种rBCG和BCG后，成年和新生小鼠血清和STLCS中IL-4水平较对照组显著降低、IFN-γ水平显著升高；无论成年鼠还是新生鼠，在CD4^ 的脾脏细胞中，IFN-γ^ 细胞的比例明显升高，而IL-4^ 细胞比例明显降低；此外，在两个年龄组小鼠，接种rBCG者脾细胞均产生了较BCG组更高水平的IFN-γ；同时，用rBCG免疫的两组小鼠脾脏CD4^ IFN-γ^ 的细胞比例也明显高于BCG免疫各组。结论：无论rBCG还是BCG通过腹腔注射免疫，均可诱导不同年龄BALB／c小鼠产生Th1免疫应答；表达在rBCG细胞壁上的Der p2被当成BCG的成分，为机体免疫系统所识别，抗原再次接触进一步刺激了Der p2特异性的Th1应答。这些结果表明，胞壁型抗原重组BCG可作为有效的疫苗，特异性地调节Th1／Th2平衡。     

TLR7介导日本血吸虫感染C57BL/6小鼠脾脏的T细胞反应

目的 探究日本血吸虫感染后小鼠脾脏TLR7对T细胞反应的调节作用。方法 使用日本血吸虫感染6周的C57BL/6小鼠（WT）和TLR7-KO小鼠,并设立相应对照组。然后观察组织病变情况,分离脾脏淋巴细胞,运用qRT-PCR、流式细胞术检测脾脏中CD4⁺T和CD8⁺T细胞数量改变以及TLR7分子表达;进一步通过流式细胞术检测WT和TLR7-KO小鼠感染前后CD4⁺T和CD8⁺T细胞CD25、CD69、CXCR5、CD40L等活化表型的变化;经PMA和离子霉素的刺激,使用细胞内细胞因子染色的方法检测CD4⁺T和CD8⁺T细胞IFN-γ、IL-4分泌情况。结果 日本血吸虫感染后,小鼠肝脏和脾脏明显增大,脾脏中CD4⁺T和CD8⁺T细胞发生大量聚集;感染后CD4⁺T和CD8⁺T细胞多种活化及功能相关指标均显著上升,且IL-4⁺CD4⁺T...     

BCG/恶性疟MSP-2、CSP多价疫苗免疫小鼠应答类型研究

目的：探讨恶性疟原虫FCC－1／HN株裂殖子表面蛋白－2（MSP－2）和环子孢子蛋白（CSP）与BCG多价疫苗在小鼠体内诱导的免疫应答的特性及抗感染的保护性免疫机制。方法：将重组pBCG／MSP－2和pBCG／CSP多价疫苗经皮下注射BALB／c小鼠，小鼠经多价疫苗免疫8周后，用流式细胞仪分析脾脏T淋巴细胞的分化，并体外培养脾脏细胞，用夹心ELISA法测定IFN－γ和IL－2的产生；用血清学方法测定免疫鼠IgG抗体的动态变化，在体外测定抗体介导的抑制实验。结果：与对照组相比，疫苗组CD4^ 和CD8^ T淋巴细胞有显著性的增高，体外培养的脾脏细胞IFN－γ有高浓度的分泌。同时，免疫鼠血清对疟原虫抗原都表现了较高水平的IgG类抗体反应，抗体对原虫的增殖明显抑制。结论：恶性疟原虫FCC－1／HNpBCG/MSP-2和pBCG/CSP多价疫苗诱导了以TH1为主的免疫应答类型。     

芪芍五味子复方制剂对病毒性心肌炎小鼠免疫调节机制的研究

目的研究黄芪、赤芍、五味子组成的芪芍五味子复方制剂调节病毒性心肌炎(viral myocarditis,VMC)小鼠外周血T淋巴细胞亚群和细胞因子表达的机制。方法 Balb/c小鼠随机分为正常对照组、病毒对照组、中药高、中、低剂量组及VitC和病毒唑联用组。小鼠接种柯萨奇病毒B3(CVB3)建立VMC模型,流式细胞仪检测外周血CD4(+Th)和CD8(+Ts)淋巴细胞亚群数目及比值,ELISA检测IFN-γ、IL-4水平,心肌作组织病理学检查。结果与正常小鼠比较,病毒对照组小鼠外周血CD4+和CD8+淋巴细胞亚群数目下降,CD4+/CD8+下降,血清IFN-γ水平升高,IL-4水平降低(P0.05),中药治疗组小鼠淋巴细胞亚群数目及CD4+/CD8+均高于病毒对照组(P0.05),IFN-γ水平高于病毒对照组及VitC和病毒唑联用组(P0.05),同时小鼠心肌炎症性病理变化明显减轻。结论芪芍五味子复方制剂能调节外周血T淋巴细胞数目及比值,诱生Th1型细胞因子IFN-γ减轻CVB3感染小鼠心肌损伤,起到保护作用。     

CD4+CD25+调节性T细胞在血吸虫免疫逃避中的作用及机制研究

目的 探讨CD4+ CD25+调节性T细胞(Tregs)在日本血吸虫免疫逃避中的作用及其机制.方法 雌性BALB/c小鼠随机分成3组,即正常对照组、感染对照组和抗CD25单克隆抗体(anti-CD25 mAb)组,各感染组每只小鼠均经腹部皮肤感染日本血吸虫尾蚴40条,感染后两周anti-CD25 mAb组每只小鼠经腹腔注射anti-CD25 mAb 300 μg,其它组注射等体积的PBS,感染后5周杀鼠冲虫,计数每只小鼠虫荷.收集脾细胞及培养上清,流式细胞术检测脾淋巴细胞中CD4+ CD25+ Tregs百分比.双抗夹心ELISA法测定脾细胞培养上清中的γ-干扰素(IFN-γ)、IL-4、IL-5、IL-10的含量.结果 Anti-CD25mAb组虫荷(23.17 ±6.94)明显低于感染对照组[(30.17 ±5.85),P=0.047];感染对照组脾淋巴细胞中CD4+ CD25+ Tregs百分比(2.68 ±0.12)％明显高于正常对照组[(1.98±0.33％),P=0.049],而anti-CD25mAb组脾淋巴细胞中CD4+ CD25+ Tregs百分比(1.28±0.30)％明显低于感染对照组(P=0.000);anti-CD25mAb组脾细胞培养上清中IFN-γ的含量(386.87±24.85) pg/mL明显高于感染对照组[(61.32±8.75) pg/mL,P=0.000],其余细胞因子组间无统计学意义.结论 anti-CD25 mAb能部分封闭CD4+ CD25+ Tregs后有利于机体清除日本血吸虫,其机制可能为增强Th1型免疫反应,宿主CD4+ CD25+ Tregs有助于日本血吸虫逃避宿主的免疫攻击.     

胞壁型rBCG经口服免疫可以诱导BALB/c小鼠产生抗原特异性TH1应答

目的观察胞壁型重组BCG(rBCG)经口服接种后对BALB/c小鼠TH细胞免疫应答的影响。方法以100 ml/L甘油为对照,分别将BCG和以膜蛋白形式表达屋尘螨抗原Der D2的rBCG经口服接种于8周龄BALB/c小鼠,109 CFU/d,连续5 d,用夹心ELISA测定小鼠血清、脾脏T淋巴细胞培养上清(SCS)和肠道相关淋巴细胞培养上清(Gcs)中IL-4、IFN-Υ水平,用双色荧光标记-流式细胞术测定脾脏淋巴细胞(SLC)和肠道相关淋巴细胞(GLC)中TH细胞亚群。结果免疫4周后,ELISA结果表明:BCG和。rBCG两组血清和SCS的IFN-Υ水平较对照组升高,IL-4水平降低;但两组小鼠GCS仅见IFN-Υ水平升高。流式细胞测定结果表明:在CD4 的SLC中,BCG和rBCG免疫小鼠的IL-12Rβ2 细胞比例升高,而CD30 细胞比例降低;在CD4 的GLC中,BCG和rBCG免疫小鼠的IFN-Υ 细胞比例升高;至免疫后8周,上述改变进一步明显,但BCG和rBCG两组之间差异无统计学意义。体外给予抗原刺激后,rBCG组小鼠变化更加显著,而BCG组则无明显改变。但GCS的IL-4水平始终无法测得;同时GLC中IL-5 细胞比例仍持续较低。结论无论rBCG还是BCG通过口服免疫,均可诱导BALB/c小鼠产生TH1优势免疫应答;而胞壁型Der p2-rBCG诱导产生的TH1优势应答具有Der p2抗原特异(记忆)性。     

血吸虫感染宿主免疫抑制现象的研究——Ⅰ.日本血吸虫感染对小鼠免疫应答的影响

作者采用微量淋巴细胞增生测定方法,在体外逐周观察感染日本血吸虫小鼠的淋巴细胞对血吸虫虫卵抗原(SEA)和促有丝分裂原(LPS,ConA)应答的变化。结果表明,小鼠感染后,脾淋巴细胞对SEA的应答于感染后第4周达峰值,随后应答逐渐下降至正常鼠的应答水平。感染后的头 10周,ConA和 LPS诱导的非特异性增生应答水平变化不明显。上述结果提示宿主感染血吸虫后免疫应答的动态变化过程。表现在感染早期,淋巴细胞对血吸虫抗原的应答明显增强;血吸虫成熟排卵后,免疫应答达峰值;而随感染时间加长,免疫应答处于抑制状态。这很可能是宿主对日本血吸虫感染的一种自发性调节作用。     

B淋巴细胞在抗CD45RB抗体诱导的移植免疫耐受中的作用

 目的: 探讨B淋巴细胞在抗CD45RB抗体诱导的移植免疫耐受中的作用。方法: 抗CD45RB抗体对BALB/c裸鼠进行预处理后制备脾脏单细胞悬液,与BALB/c小鼠T淋巴细胞和C57BL/6小鼠脾细胞混合培养,流式细胞术分析Th1、Th2、Treg和Tm淋巴细胞。以B6.μMT^-/-小鼠为受体、BALB/c小鼠为供体建立皮肤移植模型,移植后向受体鼠腹腔注射抗CD45RB单抗,监测脾淋巴细胞CD3⁺CD45RB^hi细胞比例。在混合淋巴培养过程中加入抗CD45RB单抗,分离B细胞,建立以BALB/c小鼠为供体、B6.μMT^-/-小鼠为受体的心脏移植模型,通过尾静脉注射B细胞给B6.μMT^-/-小鼠,观察受体鼠生存期和B细胞分布。结果: 在裸鼠体内用抗CD45RB抗体处理过的B淋巴细胞,与T淋巴细胞混合培养时,可使Treg和Th2淋巴细胞比例明显升高,Th1淋巴细胞的比例明显下降,Tm细胞无明显变化。在体内B淋巴细胞缺失的情况下,抗CD45RB抗体依然能够降低T细胞表面CD45RB的表达,与对照组B淋巴细胞存在组相比,抗CD45RB抗体对T淋巴细胞表面CD45RB下调更为快速,但最终CD3⁺CD45RB^hi T细胞比例无明显变化。体外抗CD45RB抗体处理过的B淋巴细胞可以延长受体鼠的生存时间。B6.μMT^-/-鼠在接受抗CD45RB抗体处理的B细胞并进行同种异体心脏移植后,B细胞可向胸腺迁移。结论: 在抗CD45RB抗体诱导的免疫耐受中,B淋巴细胞可能通过介导各T淋巴细胞亚群比例发挥着重要作用,且在中枢耐受中也起到一定作用,但是仅靠B淋巴细胞无法形成完全耐受。     

Vaccination with calpain induces a Th1-biased protective immune response against Schistosoma japonicum

A large subunit of calpain, a calcium-activated neutral proteinase, from Schistosoma japonicum was cloned and expressed in Escherichia coli. When BALB/c mice were immunized with purified recombinant calpain (r-calpain) emulsified in complete Freund's adjuvant, a significant reduction in the number of recovered worms and also in egg production per female worm was observed (P<0.01). Spleen cells of the immunized mice showed enhanced production of gamma interferon (IFN-gamma) by activated CD4(+) T cells. Considering our observation of elevated expression of inducible nitric oxide synthase mRNA in immunized mice, r-calpain-induced IFN-gamma seemed to upregulate the production of nitric oxide by macrophages and subsequently mediated the killing of schistosomulae in the lung. On the other hand, spleen cells of immunized mice showed only faint interleukin-4 production in response to r-calpain in vitro, suggesting that immunization with r-calpain alters the Th1-Th2 balance in murine hosts even during a Th2-promoting S. japonicum infection. Furthermore, histopathological study of the livers of immunized mice showed that granulomas formed around eggs were diminished in both size and number. Egg production by female worms was clearly decreased in immunized mice, suggesting that r-calpain also has antifecundity effects. Taken together, these results point to S. japonicum calpain as a potential vaccine candidate for both worm killing and disease prevention, possibly through the induction of a strong Th1-dominant environment in immunized mice.     

Effect of spleen cell populations on resolution of Cryptosporidium parvum infection in SCID mice.

Persistent infection was established in SCID mice given 10(7) Cryptosporidium parvum oocysts. Nine groups of infected SCID mice were inoculated with 10(6), 10(5), or 10(4) total spleen cells, CD8-depleted spleen cells, or CD4-depleted spleen cells from naive BALB/c donors. Infection was significantly reduced in all treatment groups. The most profound effect occurred with spleen cell preparations containing CD4 T lymphocytes but depleted of CD8 T lymphocytes.     

Immunization of mice with a DNA vaccine based on severe acute respiratory syndrome coronavirus spike protein fragment 1

According to data in GenBank, a gene encoding SARS spike protein fragment 1 (S1) was synthesized. After recombination with an immunostimulatory sequence (ISS), the gene was cloned into the plasmid pIRES to produce pIRES-ISS-S1. On confirmation of the expression of S1 protein by indirect immunofluorescence assay (IFA), after the transfection of pIRES-ISS-S1 into BHK-21 cells, the DNA vaccine was repeatedly administrated to BALB/c mice. CD4+ and CD8+ spleen T lymphocytes were analyzed by flow cytometry (FCM) to evaluate T cell-mediated immune responses, the antigen-specific responses of T cells were evaluated by cytotoxic T lymphocyte (CTL) assay, and the level of IgG in antisera from immunized mice was determined by enzyme-linked immunosorbent assay. Results showed that the counts of spleen CD4+ and CD8+ T lymphocytes were increased, that the T cell-mediated immune responses showed antigen specificity, and that IgG was significantly induced with DNA vaccines pIRES-ISS-S1 and pIRES-S1 at titers of 1:320 and 1:160, respectively. These results are promising for the protective immunization of humans.     

CD28-deficient mice generate an impaired Th2 response to Schistosoma mansoni infection

Engagement of CD28 on T cells provides a co-stimulatory signal necessary for T cell activation and differentiation. Recent findings suggest that priming of T helper (Th)2 cells is more dependent on CD28 activation than Th1 cells. The present study examines whether mice that lack expression of CD28 as a result of gene targeting are capable of generating a Th2 response characteristic during infection with the intravascular trematode parasite Schistosoma mansoni. Mutant and control mice were either inoculated in the footpad with S. mansoni eggs (a potent inducer of a Th2 response) or infected percutaneously with the parasite. Draining lymph nodes (after footpad injection) or spleen cells (after natural infection) were harvested at 12 days and 8 weeks, respectively, and examined for cytokine responses to egg antigens. CD28-deficient mice (−/−) generated diminished egg antigen-driven interleukin (IL)-4 and IL-5 production (by 5- to 17-fold, respectively) compared to CD28-expressing (+/+) littermates. In contrast, lymphocyte proliferation and interferon (IFN)-γ production to egg antigens were equivalent for mutant and control mice. Infected CD28−/− mice also had reduced immunoglobulin secretion. Serum levels of parasite antigen-specific IgG1 and polyclonal IgE were significantly diminished in CD28−/− compared to CD28+/+ mice. Lack of CD28 expression had no effect on granuloma formation around eggs trapped in the liver, but increased susceptibility of mice to primary schistosomiasis infection. These studies indicate that CD28 activation contributes to T cell priming required for generation of a Th2 response to an intravascular dwelling helminth parasite.     

重组BCG—Sj26GST疫苗诱导小鼠sIL—2R和IFN—γ的变化

目的研究日本血吸虫重组 BCG- Sj2 6 GST疫苗对小鼠脾细胞 s IL- 2 R和 IFN- γ的影响。方法第 1次实验采用 1× 10 6 和 1× 10 8CFU疫苗皮下免疫 BAL B/ C鼠 ,免疫后 8周用日本血吸虫尾蚴进行攻击感染 ,感染后 6周剖杀小鼠 ,同时设有 PBS对照组。第 2次实验用 1× 10 6 CFU疫苗皮下和静脉注射分别免疫小鼠 ,于免疫后 0、4、8、10、14和 16周各剖杀 4只 ,分离脾脏 ,用 Sj2 6或 Con A刺激脾细胞 ,用 EL ISA法检测脾细胞上清液中 s IL 2 - R和 IFN -γ含量。结果疫苗免疫 ,尾蚴攻击后 ,s IL- 2 R和 IFN- γ水平显著升高 ;动态观察发现 s IL- 2 R和 IFN- γ分别于免疫后 8～ 10周和 4～ 8周达最高水平。结论日本血吸虫重组 BCG- Sj2 6 GST疫苗可加强宿主 Th1反应 ,促进 Th1细胞分泌 IL- 2和 IFN- γ,它们与免疫细胞相互作用 ,提高宿主抗血吸虫感染的保护力     

Experimental hypersensitivity pneumonitis: influence of Th2 bias

Cultured murine CD4+ cells from Saccharopolyspora rectivirgula sensitized C3H/HeJ (Th1 bias) donors can adoptively transfer murine experimental hypersensitivity pneumonitis (EHP). We sensitized BALB/c mice (Th2 bias) with S. rectivirgula, obtained spleen and lung associated lymph node (LALN) cells, cultured the cells with specific antigen, and attempted adoptive transfer of EHP. We also treated both C3H/HeJ and BALB/c donor mice with IL4 and anti-IFNgamma before exposure to S. rectivirgula and then cultured cells from both spleen and LALN before attempted transfer of EHP. We found that cultured spleen and lung associated lymph node cells can adoptively transfer EHP in both C3H/HeJ and BALB/c mice as demonstrated by infiltration of the recipient lungs with CD4+ lymphocytes. Treatment of both mouse strains with IL4 and anti-IFNgamma did not change the ability of cultured cells to adoptively transfer EHP. We conclude that EHP induced by S. rectivirgula can occur in animals with either a Th1 or a Th2 bias and is not altered by treatment with IL4 and anti-IFNgamma. This suggests that attributes of the antigen and not genetic background or cytokine environment at the site of initial sensitization determines the results of exposure to S. rectivirgula.     

Hepatic changes in congenital Schistosoma japonicum infections in pigs

The inflammatory response in liver tissue from piglets congenitally infected with Schistosoma japonicum was examined at two different timepoints after infection. The piglets, which were the offspring of three sows infected with 9000 S. japonicum cercariae in the 10th week of gestation, were allocated into two groups (n=9 and 17) killed 5 or 11 weeks after birth, respectively. All piglets developed a low level infection,with no significant difference between the groups. Inflammatory lesions in the liver consisted mainly of granulomas in portal areas, often obliterating the portal veins, and frequently with central eggs or egg remnants. The granulomatous reaction consisted of epithelioid cells and occasional giant cells surrounded by layers of lymphocytes, eosinophils, plasma cells, and various amounts of collagen and fibroblasts. Mild to moderate infiltration of portal and septal connective tissue with eosinophils and lymphocytes was common, but the connective tissue was generally not increased. At the two timepoints, slight differences were observed in the numbers of eosinophils and lymphocytes in the granulomas and in the size of the granulomatous reaction. The same pattern of immunohistochemical labelling was seen in both groups. CD79alpha(+) B cells were scarce except in granuloma-associated lymphoid follicles;the majority of lymphocytes in granulomas and at other sites were CD3epsilon(+) T cells. The granulomatous reaction in the livers of piglets to schistosoma eggs from prenatal S. japonicum infection was similar to that seen in postnatal infection. Signs of immunomodulation of granulomas between the two timepoints of infection were not demonstrable.     

Prenatal exposure to bisphenol A up-regulates immune responses, including T helper 1 and T helper 2 responses, in mice

The effect of prenatal exposure to bisphenol A (BPA) on the immune system in mice was investigated. Virgin female mice were fed varying doses of BPA, on a daily basis, over a period of 18 days commencing on the day of pairing with stud males (day 0). On day 77, their male offspring of 8 weeks were immunized with hen egg lysozyme (HEL). Three weeks later, anti-HEL immunoglobulin G (IgG) in sera, and proliferative responses of spleen cells to the antigen, were measured. Anti-HEL IgG2a and interferon-gamma (IFN-gamma), secreted from splenic lymphocytes, were measured as indicators of T helper 1 (Th1) immune responses, while anti-HEL IgG1 and interleukin-4 (IL-4) were measured as indicators of Th2 responses. The results showed that fetal exposure to BPA was followed by significant increases in anti-HEL IgG as well as antigen-specific cell proliferation. Both Th1 responses (including anti-HEL IgG2a and IFN-gamma production) and Th2 responses (including anti-HEL IgG1 and IL-4 production) were augmented by prenatal exposure to BPA, although the augmentation of Th1 responses appeared to be greater than that of Th2 responses. Two-colour flow cytometric analysis showed that mice exposed prenatally to BPA had 29% and 100% more splenic CD3(+) CD4(+) and CD3(+) CD8(+) cells, respectively, than control animals. Similar results were obtained from females whose mothers had consumed BPA during pregnancy. These results suggest that prenatal exposure to BPA may result in the up-regulation of immune responses, especially Th1 responses, in adulthood.     

Cryptosporidium muris in adult mice: adoptive transfer of immunity and protective roles of CD4 versus CD8 cells.

The aim of this study was to investigate the role of the CD4 and CD8 T cells in immunity to cryptosporidia by using Cryptosporidium muris and a mouse model of infection. Two approaches were used, each involving the use of rat anti-T-cell surface marker monoclonal antibodies (MAbs). In the first, the adoptive transfer of immunity was studied by using the CB.17 SCID mouse (which lacks T and B cells) as the host; in the second, the effect on susceptibility of BALB/c mice to infection was examined following depletion of T cells or subsets of T cells. In adoptive immunity experiments, the conditions which differentiated between resistance associated with reconstitution of SCID mice with naive BALB/c lymphocytes and the transfer of immunity with primed lymphocytes from infected animals were determined. Primed spleen or mesenteric lymph node cells conferred better protection to recipients than naive cells when obtained from donors which had developed resistance to infection. Adoptive immunity was abrogated when Thy.1 cells or CD4 cells were depleted from primed cells, while depletion of CD8 cells could reduce the level of protection. In the study of C. muris in BALB/c mice, treatment with either anti-Thy.1 plus anti-Lyt.1 or anti-CD4 MAbs increased susceptibility to a primary infection as determined by the size and duration of oocyst production, but an anti-CD8 MAb produced an increase only in oocyst shedding. Thus, both CD4 and, to a lesser extent, CD8 cells appeared to be involved in resistance to primary and secondary C. muris infection.     

Control of Trypanosoma cruzi Infection in Mice Deprived of T-Cell Help

The role of CD4+ T lymphocytes in the resistance of BALB/c mice to Trypanosoma cruzi was examined by in vivo depletion using monoclonal anti-CD4 antibodies (MoAbs). When the administration of MoAbs was initiated 2 days before, or 5 to 12 days after the infection (dpi) with 50 bloodstream-form trypomastigotes of the Tulahuén strain, mice showed an enhanced susceptibility to the parasite. Specific IgG, but not IgM responses, were inhibited in anti-CD4-treated and infected mice. However, when anti-CD4 treatment of mice was delayed until the 8th week of infection, neither a reactivation of the infection as determined by mortality or parasitaemia, nor a modulation of the titre of anti-T. cruzi IgG antibodies was detected. Furthermore, mice chronically infected with T. cruzi and deprived of CD4+ T cells resisted the challenge with 50,000 trypomastigotes (approximately 1000 LD50). Secondary antibody responses against parasite antigens were inhibited after in vitro depletion of CD4+ cells in chronically infected mice before boosting with T. cruzi antigens. However, recipients of CD4 or T-cell-depleted spleen cells from mice chronically infected with T. cruzi were protected when challenged with the parasite. The possibility that the parasite control is maintained by long-lived B cells capable of rapid differentiation into IgG-secreting plasma cells in the absence of T helper cells is discussed considering the present data.