人AAT基因在糖尿病细胞治疗中对β细胞的免疫保护作用

目的:建立稳定表达人α1-抗胰蛋白酶(hAAT)基因的NIT-hAAT细胞系,观察hAAT基因在糖尿病细胞治疗中对β细胞的免疫保护作用。方法:构建hAAT的真核表达载体,转染并筛选得到NIT-hAAT细胞系。将该细胞系移植到糖尿病模型小鼠左肾包膜下,通过检测不同移植组小鼠的血糖、血清胰岛素水平和生存期,观察不同移植细胞对糖尿病的治疗效果;RFPCR检测移植部位的hAAT表达情况以及对小鼠左肾进行石蜡切片和苏木素-伊红(HE)染色,鉴定hAAT对NIT-1细胞的免疫保护作用。结果:糖尿病小鼠接受NIT-hAAT细胞移植后,hAAT可有效延长NIT-1细胞的存活时间,使血糖明显降低并维持至正常血糖水平,小鼠的生存率也明显提高(P<0.05);移植部位的病理HE染色结果证实hAAT可明显减轻小鼠对移植物炎症反应。但RT-PCR结果显示hAAT在体内的表达量随时间增长而出现逐渐下降,NIT-hAAT细胞最终因免疫排斥反应而失去功能。结论:NIT-hAAT细胞具有明显抑制体内免疫排斥反应,可有效延长β细胞存活时间,对胰岛细胞移植具有免疫保护作用。     

FADDDEL-GFP基因修饰在小鼠胰岛细胞移植中的作用

目的 探讨融合蛋白FADDDEL-GFP在胰岛细胞移植治疗1型糖尿病中的作用。方法 将重组子FADDDEL-GFP导入胰岛细胞NIT-1，检测基因转染前后胰岛细胞分泌胰岛素的水平。用STZ诱导1型糖尿病模型小鼠，将FADDDEL-GFP修饰的NIT-fg细胞移植于糖尿病小鼠，检测胰岛细胞移植后对糖尿病小鼠的影响。结果 转染重组子FADDDEL-GFP的NIT-1可见绿色荧光蛋白表达；移植NIT-fg细胞的糖尿病小鼠血糖降至正常，生存期延长，与对照组有明显差异。结论FADDDEL-GFP可增强机体抗同种移植排斥反应的能力。     

5-氟尿嘧啶改变胰岛β细胞的超微结构并抑制胰岛素的释放

目的: 探讨5-氟尿嘧啶(5-FU)抑制小鼠胰岛β细胞(NIT-1细胞)胰岛素分泌的相关分子机制。方法: 不同剂量的5-FU作用于NIT-1细胞,放射免疫分析法检测细胞胰岛素分泌功能的变化;Annexin V/PI双染色流式细胞术检测细胞凋亡;透射电镜观察细胞超微结构的变化;RT-PCR及Western blotting 检测胰十二指肠同源盒蛋白-1(PDX-1)mRNA和蛋白的表达。结果: 5.0-40.0 mg/L的5-FU作用24 h后,低浓度葡萄糖(5.6 mmol/L)环境下,NIT-1细胞胰岛素分泌无明显下降(P>0.05);而高浓度葡萄糖(16.7 mmol/L)刺激下的胰岛素分泌量可被5.0-40.0 mg/L 5-FU以剂量依赖性的方式所抑制(P<0.01)。细胞凋亡率明显增高(P<0.05);透射电镜可见线粒体结构改变;经10.0-40.0 mg/L的5-FU作用24 h后,PDX-1 mRNA及蛋白表达的水平均有不同程度的下降(P<0.05)。结论: 5-FU可通过诱导细胞凋亡、导致β细胞超微结构改变及数量减少而抑制胰岛β细胞高糖刺激下的胰岛素释放。下调 PDX-1 基因表达可能是5-FU在高糖条件下诱导β细胞凋亡的机制之一。     

沉默HIF-1α表达逆转缺氧诱导肝癌免疫抑制的实验研究

目的:探讨缺氧诱导因子-1(HIF-1α)表达在缺氧诱导肝癌免疫抑制中的作用,以期阐明缺氧致肝癌免疫抑 制的分子机制。方法:构建缺氧C57BL/6 小鼠移植瘤模型,缺氧探针HypoxyprobeTM-1 标记缺氧组织,免疫组化检测缺氧组织 HIF-1α表达,qPCR 检测缺氧组织肿瘤免疫因子表达;慢病毒构建稳定敲减HIF-1α的Hepa1鄄6 小鼠肝癌细胞株,并移植于 C57BL/6 小鼠,6 周后检测移植瘤瘤重,Western blot 检测移植瘤HIF鄄1琢表达,流式细胞仪检测移植瘤中肿瘤浸润免疫细胞 CD4+CD25+ Foxp3+调节性T 细胞表达,qPCR 检测缺氧组织肿瘤免疫因子表达。结果:C57BL/6 小鼠缺氧移植瘤模型构建成 功,缺氧组织HIF鄄1琢高表达,肿瘤抑制因子IFN-γ、IL-12b 和CXCL10 低表达,肿瘤促进因子IL-10、IL-1β和IL-17 高表达;敲减 HIF-1α明显抑制了移植瘤生长,降低了CD4+ CD25+ Foxp3+调节性T 细胞浸润,同时抑制了肿瘤促进因子IL-10、IL-1β和IL-17 表达,促进了肿瘤抑制因子IFN鄄酌、IL鄄12b 和CXCL10 表达。结论:缺氧可诱导肝癌组织HIF鄄1琢表达及免疫抑制,相反,沉默 HIF鄄1琢可抑制移植瘤生长并逆转肝癌免疫抑制,揭示了HIF-1α在缺氧致肝癌免疫抑制中的作用,可能为将来肝癌诊治提供 新思路。     

骨髓间充质干细胞静脉移植脊髓损伤大鼠肿瘤坏死因子α及 白细胞介素1β的表达

背景：研究认为间充质干细胞的营养支持在脊髓损伤治疗中起了主要作用,其同损伤宿主神经组织间的相互作用可导致一些不利于损伤修复的炎症因子表达减少。 目的：观察大鼠骨髓间充质干细胞静脉注射移植对脊髓损伤后肿瘤坏死因子α、白细胞介素1β 表达的影响。 方法：运用改良Allen法制备大鼠T10脊髓外伤性截瘫模型,随机分为对照组和骨髓间充质干细胞移植组,设未损伤脊髓的假手术组做对照。骨髓间充质干细胞移植组、假手术组均接受大鼠骨髓间充质干细胞静脉注射移植,对照组静脉注射等量PBS。 结果与结论：对照组和骨髓间充质干细胞移植组损伤脊髓肿瘤坏死因子α、白细胞介素1β蛋白表达较假手术组有明显增加(P < 0.05);骨髓间充质干细胞移植组与对照组比较, 肿瘤坏死因子α、白细胞介素1β蛋白表达受到明显抑制(P < 0.05)。提示大鼠骨髓间充质干细胞静脉移植后能使损伤脊髓局部的肿瘤坏死因子α、白细胞介素1β表达程度降低。这可能是改变脊髓损伤区的微环境,减少脊髓继发性损伤,促进损伤大鼠运动功能恢复的机制之一。     

腺病毒介导鼠胰岛素样生长因子1基因对胰岛β细胞的保护作用**

背景：研究表明自身高表达胰岛素样生长因子1的小鼠对药物诱导糖尿病有一定的预防作用。 目的：观察腺病毒介导鼠胰岛素样生长因子1基因对胰岛β细胞损伤的保护作用。 方法：①体外实验：以Ad-rIGF-1、Ad-eGFP直接感染鼠胰岛β细胞标准细胞株-R1Nm5F细胞,然后两组再分别加入0,1.5 mmol/L链脲佐菌素。②体内预防实验：将60只昆明小鼠随机分为空白对照组(不做任何处理)、糖尿病对照组(制作糖尿病模型)、空载体对照组(仅腹腔注射Ad-eGFP重组腺病毒液)、Ad-rIGF-1组(于糖尿病模型制作前2周腹腔注射Ad-rIGF-1重组腺病毒液)。③体内治疗实验：将75只昆明小鼠随机分组：空白对照组(不做任何处理)、糖尿病对照组、胰岛素组、Ad-rIGF-1组、Ad-rIGF-1联合胰岛素组。后3组制作糖尿病模型后给予相应干预。 结果与结论：①鼠胰岛素样生长因子1在胰岛β细胞有效表达,并具有抑制链脲佐菌素诱导胰岛β细胞凋亡的作用。②Ad-rIGF-1组糖尿病发病率低,平均血糖水平低,胰腺炎症浸润程度轻。③与糖尿病对照组、胰岛素组相比,Ad-rIGF-1组和Ad-rIGF-1联合胰岛素组胰腺炎症浸润程度轻,鼠胰岛素样生长因子1在胰岛局部高表达;胰岛素组、Ad-rIGF-1组、Ad-rIGF-1联合胰岛素组血清C-肽水平低,组间比较无明显差别(P > 0.05)。表明胰岛β细胞局部表达鼠胰岛素样生长因子1能够保护胰岛β细胞功能,提高细胞存活率,预防和减轻链脲佐菌素诱导的昆明小鼠1型糖尿病。但鼠胰岛素样生长因子1基因转导与胰岛素皮下注射联合应用对糖尿病早期残存胰岛细胞功能的保护效果不明显。      

内质网应激激活STING信号通路并降低胰岛β细胞活力

目的：鉴定胰岛β细胞中干扰素基因刺激因子（STING）信号通路相关基因的表达及其与内质网应激的相互作用,研究2个通路间的相互作用对胰岛β细胞活力的影响。方法：通过生物信息学分析来源于人的胰岛单细胞RNA测序数据集,得到STING信号通路相关基因在胰岛β细胞中的表达变化;用免疫荧光法检测并比较野生型小鼠和db/db糖尿病小鼠胰岛β细胞中STING蛋白的表达差异;用STING特异性激动剂5,6-二甲基呫吨酮-4-乙酸（DMXAA）处理3种常用的小鼠胰岛β细胞系（NIT-1、Min6及beta-TC-6）,并通过RT-qPCR和Western blot分别检测其STING信号通路相关蛋白的mRNA和蛋白表达水平变化;用毒胡萝卜素（TG）诱导上述β细胞系内质网应激,通过Western blot检测STING信号通路相关蛋白的表达及磷酸化水平,并通过CCK-8法检测胰岛β细胞活力。结果：人胰岛β细胞中存在STING信号通路主要基因mRNA的表达,但在健康人群和糖尿病患者的表达水平无显著差异。免疫荧光结果表明,野生型小鼠和db/db小鼠胰岛β细胞的STING蛋白均在细胞核周边富集,且在db/db小...     

针刺提高2型糖尿病模型大鼠胰岛β细胞胰岛素的表达

背景：针刺治疗2型糖尿病具有很好的疗效。 目的：观察针刺对2型糖尿病模型大鼠胰岛β细胞胰岛素表达的影响。 方法：将糖尿病模型大鼠按随机化原则分为针刺组、西药组、模型组,同时设置正常对照组。针刺组大鼠取足三里、内庭和胰俞穴给予针刺治疗,西药组用罗格列酮0.2 mg/kg灌胃,模型组用双蒸水2 mL/kg灌胃,均1次/d,连续4周。 结果与结论：①血糖：针刺组明显低于模型组、西药组(P < 0.05)。②血脂：针刺组胆固醇和三酰甘油低于模型组 (P < 0.05);高密度脂蛋白胆固醇明显高于模型组(P < 0.01)。针刺组三指标与西药组比较差异无显著性意义。③胰岛β细胞胰岛素表达：针刺组显著高于模型组和西药组(P < 0.05)。④胰岛形态：模型组与西药组胰岛结构不完整,结构破坏,胰岛素染色效果差;针刺组胰岛结构趋向完整,胰岛素染色颗粒明显。说明针刺可显著提高2型糖尿病模型大鼠胰岛β细胞胰岛素表达水平,有效改善胰岛β细胞功能。     

NOD8对LPS诱导巨噬细胞释放NO、TNF-α和IL-1β的影响

 目的： 探讨NOD8对脂多糖（LPS）诱导巨噬细胞释放一氧化氮（NO）、肿瘤坏死因子α（TNF-α）和白细胞介素1β（IL-1β）的影响。方法： pEGFP-C2及pEGFP-NOD8重组质粒分别转染小鼠巨噬细胞RAW264.7,以LPS刺激RAW264.7细胞0、6、12、24 h后,采用Griess reagent法测定观察细胞分泌的NO水平;ELISA法检测IL-1β 和 TNF-α 的含量;荧光法测定活化的caspase-1水平; Western blotting检测NOD8蛋白表达及NF-κB  p65亚基的核转位情况。结果： (1)与转染pEGFP-C2空质粒组比较,转染pEGFP-NOD8质粒组NOD8蛋白表达明显增加。(2) LPS刺激6、12、24 h后,RAW264.7细胞释放NO、IL-1β及TNF-α均明显增加;而在pEGFP-NOD8+LPS组RAW264.7细胞, NO于12、24 h 的释放显著降低,IL-1β于6、12、24 h的释放也明显降低,TNF-α的释放则无明显变化。（3）在LPS刺激6、12、24 h后, RAW264.7细胞caspase-1活化水平均明显升高,胞浆NF-κB p65亚基表达明显减少,表明p65核转位增加;而pEGFP-NOD8+LPS组可显著抑制caspase-1的活化以及NF-κB p65亚基的核转位,差异有统计学意义。结论： NOD8可抑制LPS诱导的巨噬细胞NO与IL-1β释放,其作用机制可能与NOD8抑制caspase-1及NF-κB 的活化有关。     

转录因子FOXO1对胰岛β细胞致炎因子产生的影响

目的观察转录因子FOXO1(forkhead box O1)对胰岛β细胞炎症因子产生的影响,探讨转录因子FOXO1在糖尿病发病机制中的作用。方法运用脂质体转染方法,将pcDNA-FOXO1真核表达载体瞬时转染至NIT-1细胞,通过Western blot检测细胞中FOXO1的过表达情况;以LPS分别处理重组质粒(pcDNA-FOXO1)、空质粒(pcDNA3.1)转染以及未转染的NIT-1细胞24 h后,应用ELISA法检测3组细胞致炎因子IL-1β、TNF-α表达情况。以LPS和PBS分别处理NIT-1细胞24 h后,ELISA测定两组细胞致炎因子IL-1β、TNF-α表达情况,Western blot比较两组细胞FOXO1蛋白表达及磷酸化水平的差异。结果 FOXO1在瞬时转染48 h的NIT-1细胞中实现了过表达;经LPS刺激后,重组质粒转染的NIT-1细胞产生的IL-1β和TNF-α显著高于空质粒转染和未转染组(P<0.01);经LPS处理24 h后的NIT-1细胞产生了致炎因子IL-1β和TNF-α,而PBS处理组未见表达。LPS处理组中FOXO1蛋白表达高于PBS处理组,但磷酸化水平显著低于PBS处理组(P<0.01)。结论炎症状态下,过表达转录因子FOXO1可增加胰岛β细胞致炎因子的产生,这主要与非磷酸化FOXO1的相对增多有关,它有望成为糖尿病抗炎治疗的新靶点。     

The immunosuppressive and protective ability of glucose-regulated protein 78 for improvement of alloimmunity in beta cell transplantation

An insulinoma cell line, NIT-1, transfected with glucose-regulated protein 78 (GRP78) was established, namely NIT-GRP78, and used to study the immunosuppressive and protective ability of GRP78. In extended cytotoxic T lymphocyte (CTL) killing assay, NIT-1-primed lymphocytes were more cytotoxic in killing beta cells than NIT-GRP78-primed lymphocytes. Severe necrosis was observed only when the NIT-1-primed lymphocytes were cultured with NIT-1 beta cells, but not with NIT-GRP78 cells. In addition, an increase of interleukin (IL)-4 secretion from beta cell-primed splenocytes when GRP78 presence was observed in cytokine enzyme-linked immunosorbent assay (ELISA). Diabetic mice reached normoglycaemia promptly and gained weight after transplantation of either NIT-1 or NIT-GRP78 cells. However, the recipient mice transplanted with NIT-GRP78 cells lived much longer than those recipients transplanted with NIT-1 cells, which was due apparently to prolonged insulin production by the transplanted NIT-GRP78 cells. In fact, we observed a significant increase of insulin concentration after glucose stimulation of diabetic mice received NIT-GRP78 cells at day 7 post-transplantation. From the results we propose that GRP78 could have a dual function in both protecting NIT-1 cells from CTL-mediated lysis and stimulating a population of T helper 2 cells to down-regulate the immune response to the transplanted beta cells.     

Human α1‐antitrypsin modifies B‐lymphocyte responses during allograft transplantation

B‐lymphocyte activities are associated with allograft rejection. Interleukin‐10 (IL‐10) ‐expressing B cells, however, exhibit regulatory attributes. Human α1‐antitrypsin (hAAT), a clinically available anti‐inflammatory circulating glycoprotein that rises during acute‐phase responses, promotes semi‐mature dendritic cells and regulatory T (Treg) cells during alloimmune responses. Whether B lymphocytes are also targets of hAAT activity has yet to be determined. Here, we examine whether hAAT modulates B‐cell responses. In culture, hAAT reduced the lipopolysaccharide‐stimulated Ki‐67⁺ B‐cell population, IgM release and surface CD40 levels, but elevated IL‐10‐producing cells 1.5‐fold. In CD40 ligand‐stimulated cultures, hAAT promoted a similar trend; reduction in the Ki‐67⁺ B‐cell population and in surface expression of CD86, CD80 and MHCII. hAAT increased interferon‐γ‐stimulated macrophage B‐cell activating factor (BAFF) secretion, and reduced BAFF‐receptor levels. Draining lymph nodes of transgenic mice that express circulating hAAT (C57BL/6 background) and that received skin allografts exhibited reduced B‐lymphocyte activation compared with wild‐type recipients. BSA‐vaccinated hAAT transgenic mice exhibited 2.9‐fold lower BSA‐specific IgG levels, but 2.3‐fold greater IgM levels, compared with wild‐type mice. Circulating Treg cells were 1.3‐fold greater in transgenic hAAT mice, but lower in B‐cell knockout (BKO) and chimeric hAAT–BKO mice, compared with wild‐type mice. In conclusion, B cells are cellular targets of hAAT. hAAT‐induced Treg cell expansion appears to be B‐cell‐dependent. These changes support the tolerogenic properties of hAAT during immune responses, and suggest that hAAT may be beneficial in pathologies that involve excessive B‐cell responses.     

Autoreactive cytotoxic T lymphocytes acquire higher expression of cytotoxic effector markers in the islets of NOD mice after priming in pancreatic lymph nodes

Cytotoxic T lymphocytes (CTLs) that cause type 1 diabetes are activated in draining lymph nodes and become concentrated as fully active CTLs in inflamed pancreatic islets. It is unclear whether CTL function is driven by signals received in the lymph node or also in the inflamed tissue. We studied whether the development of cytotoxicity requires further activation in islets. Autoreactive CTLs found in the islets of diabetes-prone NOD mice had acquired much higher expression of the cytotoxic effector markers granzyme B, interferon γ, and CD107a than had those in the pancreatic lymph node (PLN). Increased expression seemed to result from stimulation in the islet itself. T cells held up from migrating from the PLN by administration of the sphingosine-1-phosphate agonist FTY720 did not increase expression of cytotoxic molecules in the PLN. Stimulation did not require antigen presentation or cytokine secretion by the target β cells because it was not affected by the absence of class I major histocompatibility complex expression or by the overexpression of suppressor of cytokine signaling-1. Activation of CD40-expressing cells stimulated increased CTL function and β-cell destruction, suggesting that signals derived from CD40-expressing cells promote the acquisition of cytotoxicity in the islet environment. These data provide in vivo evidence that stimulation of cytotoxic effector molecule expression occurs in inflamed islets and is independent of β cells.     

胰岛β细胞退分化在β细胞功能衰竭中的作用

正随着生活水平的提高和饮食结构的改变,2型糖尿病患病率逐年增高,预防和治疗2型糖尿病已经成为一个亟待解决的问题~([1-2])。除了胰岛素抵抗之外,胰岛β细胞功能衰竭亦是引起2型糖尿病发生发展的中心环节。通常认为由胰岛β细胞凋亡引起的胰岛细胞数量减少是引起糖尿病的重要致病机制~([3]),然而近年来研究发现,胰岛β细胞凋亡程度与胰岛素下降程度不平行,因而胰岛素分泌功能的研究成为热点。引起β细胞分泌功能缺陷的作用机制     

Pyruvate kinase,muscle isoform 2 promotes proliferation and insulin secretion of pancreatic β-cells via activating Wnt/CTNNB1 signaling

Failure of pancreatic β-cells is closely associated with type 2 diabetes mellitus (T2DM), an intractable disease affecting numerous patients. Pyruvate kinase, muscle isoform 2 (PKM2) is a potential modulator of insulin secretion in β-cells. This study aims at revealing roles and possible mechanisms of PKM2 in pancreatic β-cells. Mouse pancreatic β-cell line NIT-1 was used for high glucose treatment and PKM2 overexpression by its specific expression vector. Cell proliferation by Thiazolyl blue assay, cell apoptosis by annexin V-fluorescein isothiocyanate/prodium iodide staining and insulin secretion assay by ELISA were performed in each group. The mRNA and protein levels of related factors were analyzed by real-time quantitative PCR and western blot. Results showed that Pkm2 was inhibited under high glucose conditions compared to the untreated cells (P < 0.01). Its overexpression significantly suppressed NIT-1 cell apoptosis (P < 0.01), and induced cell proliferation (P < 0.05) and insulin secretion (P < 0.05). Related factors showed consistent mRNA expression changes. Protein levels of β-catenin (CTNNB1), insulin receptor substrate 1 (IRS1) and IRS2 were all promoted by PKM2 overexpression (P < 0.01), indicating the activated Wnt/CTNNB1 signaling. These results indicated the inductive roles of PKM2 in pancreatic β-cell NIT-1, including promoting cell proliferation and insulin secretion, and inhibiting cell apoptosis, which might be achieved via activating the Wnt/CTNNB1 signaling and downstream factors. This study offers basic information on the role and mechanism of PKM2 in pancreatic β-cells, and lays the foundation for using PKM2 as a potential therapeutic target in T2DM.     

miR-375 enhances palmitate-induced lipoapoptosis in insulin-secreting NIT-1 cells by repressing myotrophin (V1) protein expression

Lipoapoptosis of pancreatic β cells caused by elevated circulating free fatty acids (FFAs) has now been recognized to be a pivotal factor contributing to β cellular dysfunction and β-mass lose in type 2 diabetes. Although recent studies suggested an important role for the ceramide pathway in the late destructive phase of lipid overload in the pancreatic β cells, the overall underlying mechanisms leading to lipoapoptosis, however, remained poorly understood. mir-375 was recently characterized to be a pancreatic islet-specific miRNA implicated in the regulation of insulin secretion and β-mass turnover. In the present study we further examined its effect on palmitate-induced lipoapoptosis in NIT-1 cells, a NOD-derived β-cell line. It was found that NIT-1 cells with ectopic mir-375 expression were much more susceptible to palmitate-induced lipoapoptosis. In contrast, knockdown of endogenous pri-mir-375 expression by a modified antisense oligo, 2''-O-me-375, almost completely protected NIT-1 cells from palmitate-induced lipoapoptosis. We further demonstrated that mir-375 could target V1 mRNA and repress its translation. Consistent with this assumption, NIT-1 cells transfected with 2''-O-me-375 showed significant higher levels of V1 protein after palmitate induction. Together, our data suggest that mir-375 could be a potential therapeutic target for prevention and intervention of β-cell dysfunction and β-mass lose in type 2 diabetes.     

Corrective effects of interleukin-12 on age-related deficiencies in IFN-gamma production and IL-12Rbeta2 expression in virus-specific CD8+ T cells.

Interleukin-12 receptor beta2 (IL-12Rbeta2) has been shown to be selectively expressed on Th1 T cell subsets, and we have previously shown that influenza-specific CD8+ cytotoxic T lymphocyte (CTL) deficiency in old mice was associated with deficient Th1 (interferon-gamma [IFN-gamma]) cytokine production. This study tested whether IL-12Rbeta2 expression was also deficient in CD8+ CTL from old mice and the effect of IL-12 treatment on these responses. Splenic lymphocytes from influenza-primed old and young BALB/c mice were stimulated with influenza virus in vitro with and without IL-12 and then enriched for CD8+ T cells. IFN-gamma was significantly reduced, whereas IL-4 and IL-12p40 (an antagonist of IL-12 function) were evaluated in old when compared with young mice. This was true for secreted protein measured by ELISA and for mRNA levels quantitated by RT-PCR. IL-12Rbeta2 mRNA expression in CD8+ CTL was also significantly reduced in old mice. IL-12 treatment in vitro caused significant upregulation of IFN-gamma and IL-12Rbeta2 and downregulation of IL-4 in CD8+ T cells from old mice and young mice. The present demonstration of an age-related downregulation in IL-12Rbeta2 expression and our previous data showing reduced IFN-gamma and elevated IL-4 production provide strong evidence that CD8+ CTL deficiency in aging results from a Th1/Th2 cytokine production switch. Agents that increase IL-12Rbeta2 expression and redirect Th2 to Thl immune responses are likely to enhance CD8+ CTL-mediated control of viral infections in aging.