蛋白酪氨酸磷酸酶SHP-2对Ang Ⅱ刺激的心肌成纤维细胞增殖的影响

目的: 探讨含有Src同源结构域2的蛋白酪氨酸磷酸酶2 (Src homology 2 domain-containing protein tyrosine phosphatase 2, SHP-2) 对血管紧张素Ⅱ (angiotensin Ⅱ, Ang Ⅱ) 刺激的心肌成纤维细胞(cardiac fibroblasts,CFs)增殖的作用。方法: 差速贴壁法体外培养心肌成纤维细胞,以波形蛋白(vimentin)鉴定CFs纯度; MTT法检测Ang Ⅱ作用下心肌成纤维细胞增殖率,采用重组腺病毒过表达SHP-2和SHP-2抑制剂NSC-87877分别对Ang Ⅱ作用下的细胞增殖的影响。结果: Ang Ⅱ 对CFs增殖的促进作用有剂量依赖性,其促进细胞增殖的最高浓度为10^-7 mol/L;在AngⅡ 的刺激下,SHP-2可以促进心肌成纤维细胞增殖,并且突变体组比野生型组增殖更明显(P<0.01)。 SHP-2抑制剂NSC-87877达到50 μmol/L时可以明显抑制Ang Ⅱ刺激下的CFs增殖。结论: Ang Ⅱ的促CFs增殖作用是通过SHP-2调控的。     

蛋白酪氨酸磷酸酶SHP-2在乳腺癌细胞移动及粘附中的作用

目的 :检测蛋白酪氨酸磷酸酶SHP - 2在IL - 1所促发的细胞移动中的作用。方法 :首先构建重组质粒SHP - 2 -GFP以及SHP - 2C >S -GFP ,并分别转入MCF - 7乳腺癌细胞中 ,建立两种细胞株 ,即 :SHP - 2 -GFP -MCF - 7和SHP - 2C >S -MCF -7。利用细胞移动实验、细胞粘附实验、免疫沉淀、蛋白印迹等生物学实验方法 ,从形态学、蛋白表达量、磷酸化水平等方面分析细胞形态变化、E -钙粘蛋白和基质金属蛋白酶MMP - 1、9在 3种细胞株中的表达情况和细胞因子IL - 1刺激后 3种细胞株中的表达情况 ,进而分析SHP - 2蛋白酪氨酸磷酸酶…     

蛋白酪氨酸磷酸酶SHP-2在乳腺癌细胞移动及粘附中的作用

目的：评价大鼠胎脑神经细胞(FBC)与几丁质(Chitin)多孔体、胶原蛋白(Collagen Protein)海绵及明胶(Glutin)海绵的细胞相容性；研究几丁质和胶原蛋白与大鼠FBC复合体(C-FBC，CP-FBC)脑内移植对脑损伤的修复作用。为中枢神经系统(CNS)组织工程材料的选择提供实验依据。     

臭灵丹中黄酮类化合物对人喉癌细胞Hep-2凋亡的影响及机制

目的:探讨中药臭灵丹中黄酮类化合物诱导人喉癌细胞Hep-2凋亡的机制。方法:MTT法检测分离自臭灵丹的黄酮类化合物3,5-二羟基-6,7,3',4'-四甲氧基黄酮(HTMF)对2种正常细胞的毒性和对3种肿瘤细胞株的增殖抑制作用;采用流式细胞仪检测化合物对Hep-2细胞凋亡率的影响;Western blotting法检测凋亡蛋白caspase-3和caspase-9的变化。结果:HTMF显著抑制Hep-2细胞的增殖并呈浓度、时间双重依赖性关系,但对正常细胞Vero和EVC304的毒性较小,对A549和HepG2细胞抑制作用小。流式细胞仪检测结果显示HTMF对Hep-2细胞有促凋亡作用并呈明显的量效、时效关系。Western blotting结果显示HTMF可诱导Hep-2细胞中caspase-3和caspase-9蛋白的活化,并呈时间依赖性关系。结论:HTMF对人喉癌细胞Hep-2的生长有显著的抑制作用,其机制可能通过激活caspase-9进而活化caspase-3诱导Hep-2细胞凋亡。     

细菌氧化还原蛋白azurin诱导U2OS细胞凋亡过程中caspase-3的活化

目的:探讨细菌氧化还原蛋白azurin 诱导人骨肉瘤细胞U2OS凋亡过程中是否有caspase-3 的活化。方法:Annexin-V/PI FCM 检测细胞凋亡情况,用Western blot 分析caspase-3 酶原的变化,半定量RT-PCR 检测caspase-3 mRNA 水平的改变,比色法测定caspase-3 的相对活性。结果:用0、25、50、100、200 mg/L azurin处理U2OS细胞24 h,随药物浓度的增加,caspase-3 酶原的蛋白水平减少,caspase-3 的mRNA 水平增加(P<0.01) 。用100 mg/L azurin分别处理细胞3、6、12、24、48 h,caspase-3活性于6 h开始升高,24 h 达高峰(为对照组的7.2倍,P<0.01),48 h 仍高于对照组(P<0.01);用不同浓度的azurin 处理细胞,caspase-3 活性呈浓度依赖性升高。结论:Azurin诱导人骨肉瘤U2OS细胞凋亡过程中有caspase-3 的活化,caspase-3在azurin诱导的骨肉瘤细胞凋亡机制中发挥了重要的作用。     

CD45蛋白酪氨酸磷酸酶与小表皮γδT细胞发育的关系

探讨ＣＤ４５分子在γδＴ细胞发育过程中的作用。方法采用ＣＤ４５基因敲除变种鼠，观察其Ｖγ３树突状表皮Ｔ细胞，这类唯一居住于鼠类表皮组织的γδＴ细胞的变化。结论ＣＤ４５分子虽在αβＴ细胞发育中起重要作用，但对包括Ｖγ３ＤＥＴＣ及Ｖγ２Ｔ细胞在内的γδＴ细胞之成熟过程可能并非必需。     

CD45蛋白酪氨酸磷酸酶与小鼠表皮γδT细胞发育的关系

目的探讨ＣＤ４５分子在γδＴ细胞发育过程中的作用。方法采用ＣＤ４５基因敲除变种鼠，观察其Ｖγ３树突状表皮Ｔ细胞（Ｖγ３ＤＥＴＣ），这类唯一居住于鼠类表皮组织的γδＴ细胞的变化。以原位免疫标记观察其表皮内Ｖγ３ＤＥＴＣ的分布密度和免疫表型，以ＲＴ－ＰＣＲ检测表皮细胞中Ｖγ３ＴＣＲｍＲＭＡ的表达水平，以双荧光ＦＣＭ测定Ｖγ３ＤＥＴＣ在表皮细胞中及Ｖγ２Ｔ细胞在淋巴结细胞中所占比例，并与野生型鼠作对照。结果ＣＤ４５缺失鼠表皮内Ｖγ３ＤＥＴＣ的密度、免疫表型，表皮细胞Ｖγ３ＴＣＲｍＲＮＡ表达水平以及Ｖγ３ＤＥＴＣ和Ｖγ２Ｔ细胞分别在表皮细胞及淋巴结细胞中的比例与野生型鼠无明显差异。结论ＣＤ４５分子虽在αβＴ细胞发育中起重要作用，但对包括Ｖγ３ＤＥＴＣ及Ｖγ２Ｔ细胞在内的γδＴ细胞之成熟过程可能并非必需     

依托度酸诱导SMMC7721细胞凋亡的分子机理研究

目的：探讨选择性环氧合酶抑制剂依托度酸（etodolac）诱导肝癌SMMC7721细胞凋亡的分子机理。 方法： 采用流式细胞术、DNA琼脂糖凝胶电泳法测定细胞凋亡情况；Western blotting法检测不同浓度etodolac处理后凋亡相关蛋白Bcl-2、Bax表达的变化；流式细胞术检测半胱氨酸酶-3 (caspase-3)活性的变化；TransAMTM NF-κB p65/p50核转录因子活性检测试剂盒检测核因子-κB (NF-κB)活性变化。 结果： 流式细胞术显示etodolac（0.25、0.50、1.0、2.0 mmol/L）作用SMMC7721细胞48 h后，与对照组（0 mmol/L）相比，出现明显凋亡峰（P<0.01 vs control）；高浓度etodolac处理后DNA琼脂糖凝胶电泳出现明显的DNA Ladder, 凋亡相关蛋白Bcl-2表达下降，Bax表达增加；与对照组相比，低浓度组（0.25 mmol/L）caspase-3活性未明显活化（P>0.05），NF-κB活性也未受明显抑制（P>0.05），随着etodolac浓度的增大（0.50、1.0、2.0 mmol/L），caspase-3活性明显活化（P<0.05 vs control）； NF-κB活性明显受到抑制（P<0.05 vs control）。经Pearson 相关分析，caspase-3活性和NF-κB活性呈显著负相关（r=0.919, P<0.01）。 结论： 选择性COX-2抑制剂etodolac可能通过抑制NF-κB结合活性，调节Bcl-2、Bax蛋白表达，活化caspase-3，从而诱导肝癌SMMC7721细胞凋亡。     

管花苷B对抗H202诱导的PCI2细胞凋亡

目的:观察肉苁蓉提取物管花苷B对H:O:诱导的PCI2细胞损伤的影响.方法:用MTr法检测细胞存活率,以激光共聚焦显微镜荧光染色法检测细胞内活性氧的产生和线粒体膜电位的变化,DNA琼脂糖凝胶电泳和流式细胞仪检测细胞凋亡的发生,并用荧光酶标仪测定caspase-3的活性.结果:100 μmol稬-1H2O2处理细胞24 h显著降低细胞的存活率;诱导细胞发生凋亡,凋亡率达48.O％;细胞内活性氧水平及caspase-3的活性显著升高;而线粒体膜电位却明显降低,红／绿荧光强度的比值由正常的5.97降低为0.41左右.而预先给予l、10或100 mg.L-1浓度的管花苷B处理细胞12 h,可显著提高细胞存活率;并可有效抑制DNA ladder的发生;流式细胞仪检测凋亡率分别降低到30.9％、18.3％和6.2％;激光共聚焦显微镜结果显示管花苷B可明显降低细胞内活性氧的水平;并可逐渐恢复线粒体的高能量状态;easpase-3的活性不断降低,并呈现了一定的剂量依赖性.结论:管花苷B能显著地抑制H2O2诱导的PCI2细胞凋亡,其神经细胞保护作用可能与其降低细胞内活性氧水平,维持线粒体膜电位的高能状态和抑制caspase-3的活性有关.     

Et-DHA通过激活线粒体途径和T细胞granzyme B诱导HepG2细胞凋亡

 目的：本研究探讨了二十二碳六烯酸乙酯（Et-DHA）对人肝癌HepG2细胞凋亡的影响。方法：HepG2细胞用于检测Et-DHA的抑癌活性,MTT法检测Et-DHA对HepG2细胞的直接抑制作用,Hoechst 33258荧光染色观察细胞的形态特征,ELISA法检测Et-DHA处理后HepG2细胞的活性氧簇（ROS）释放量、总超氧化物歧化酶（SOD）和caspase-9活性,Western blotting法检测胞质和线粒体中Bax、Bak、Bid、Bcl-2、Smac和细胞色素C(Cyt C),以及胞质中cleaved caspase-8、cleaved caspase-9和cleaved caspase-3的水平;T细胞与HepG2细胞共培养,进一步观察Et-DHA处理后T细胞的增殖对HepG2细胞活性的影响,并检测了颗粒酶（granzyme）B的水平。结果：Et-DHA显著抑制HepG2细胞的生长（P＜0.05）,这种抑制作用具浓度效应和时程效应;Et-DHA处理后HepG2细胞的ROS释放量增加,但总SOD活性无明显变化,caspase-9活性显著上升（P＜0.05）;线粒体上的促凋亡蛋白Bax、Bak和Bid水平增加,而抑凋亡蛋白Bcl-2以及线粒体中Cyt C和Smac的水平降低,胞质中的Cyt C、Smac、cleaved caspase-8、cleaved caspase-9、cleaved caspase-3以及cleaved Bid水平呈剂量性升高。另外 T细胞和HepG2细胞共培养组在Et-DHA的诱导下,HepG2细胞的凋亡程度与Et-DHA单独作用时相比进一步增加。在Et-DHA刺激下,T细胞内granzyme B上调,释放到HepG2 细胞内的granzyme B明显增多。结论:Et-DHA可能主要通过线粒体内源性途径以及caspase-8途径,激活caspase-3,诱导HepG2细胞凋亡,以及通过间接活化T细胞,促使 granzyme B增多,从而增强对HepG2细胞的毒性作用。     

The tyrosine phosphatase SHP-2 regulates differentiation and apoptosis of individual primary T lymphocytes

Although phosphatases are key players of intracellular processes, not much is known about the phosphatase SHP-2 during T cell differentiation. Here we show that ectopic over-expression of SHP-2 in primary T helper cells directly reduced the frequency of individual lymphocytes expressing pro-inflammatory cytokines after antigen-specific stimulation by a mechanism impairing activation of protein kinase C. In addition we demonstrate that SHP-2 mediates enhanced migration upon CXCR4 signaling in a G-protein-dependent manner. Most strikingly, SHP-2 mediated a dramatic increase in apoptosis by highly enhanced activation of caspases. Co-immunoprecipitations of SHP-2 and c-Cbl from primary T helper cells demonstrated that SHP-2 strongly interacts with the ubiquitin ligase c-Cbl, indicating that c-Cbl could mediate the negative signals of SHP-2. Our results show that SHP-2 signal transduction regulates central checkpoints of T cell differentiation by the activation of distinct signaling cascades.     

SHP-2酪氨酸磷酸酶激活突变导致小鼠髓系异常增殖

目的: 观察激活突变SHP-2酪氨酸磷酸酶是否参与髓系异常增殖的发生。方法: 以野生型(WT)和SHP-2^D61G/+突变型C57BL/6小鼠为研究对象,计数外周血白细胞,比较脾大小,流式细胞术检测外周血及骨髓髓系来源细胞表面标志分子(Mac-1、Gr-1),并统计外周血Mac-1和Gr-1阳性细胞率及骨髓细胞中红系 (Ter119)、髓系 (Mac-1、Gr-1)、T(CD3)、B(B220)淋巴细胞系的阳性细胞率,观察骨髓造血干/祖细胞的集落形成(CFU)能力,Western blotting检测外周血白细胞经白细胞介素 3(IL-3)和5 μg/L,刺激后磷酸化的丝氨酸/苏氨酸蛋白激酶B(p-Akt)和磷酸化的细胞外信号调节激酶(p-ERK)表达水平。结果: SHP-2^D61G/+突变16周龄组小鼠较WT组外周血白细胞数增多(P<0.05),脾明显增大,同时外周血白细胞的Mac-1和Gr-1阳性细胞率增加(P<0.05),骨髓细胞中Mac-1和Gr-1的阳性细胞率也增多,但红系、淋巴细胞系的变化不明显。同时骨髓中粒-单核细胞集落形成单位(CFU-GM)较正常对照组明显增加,白细胞经IL-3刺激后Akt和ERK蛋白磷酸化水平升高。结论: SHP-2D61G/+突变可能通过MAPK及PI3K的活化而导致小鼠髓系异常增殖。     

Src homology 2 domain-containing protein tyrosine phosphatase substrate 1 regulates the induction of Langerhans cell maturation

Recently, we reported that Src homology 2 domain-containing protein tyrosine phosphatase substrate 1 (SHPS-1) plays an important role in the migration of Langerhans cells (LC). Here, we show that SHPS-1 is involved in the maturation of LC. Immunofluorescence analysis on epidermal sheets for I-A or CD86 revealed that LC maturation induced by 2,4-dinitro-1-fluorobenzene (DNFB) or by TNF-alpha was inhibited by pretreatment with an anti-SHPS-1 monoclonal antibody (mAb) or with CD47-Fc fusion protein, a ligand for SHPS-1. Further, FACS analysis demonstrated that I-A(+) LC that had emigrated from skin explants expressed CD80 or CD86, whereas CD47-Fc protein reduced CD80(high+) or CD86(high+) cells. CD47-Fc protein also reduced the up-regulation of surface CD80 or CD86 by LC remaining in the skin explants. In SHPS-1 mutant mice, we observed that the up-regulation of surface CD86 and CCR7 by LC induced by DNFB as well as that of surface CD80 and CD86 by LC in skin explants was attenuated. Finally, contact hypersensitivity (CHS) response was suppressed in SHPS-1 mutant mice and in wild-type mice treated with an anti-SHPS-1 mAb. These observations indicate that SHPS-1 plays an important role in the maturation of LC ex vivo and in vivo, and that SHPS-1-CD47 interaction may negatively regulate CHS.     

Protein phosphatase-2A regulates protein tyrosine phosphatase activity in Lewis lung carcinoma tumor variants

Cellular adherence and motility are processes that are controlled by focal adhesion assembly and disassembly. Consequently, the dynamics of focal adhesions regulate tumor cell metastasis and are influenced by the tyrosine phosphorylation state of paxillin. Metastatic LLC cells are more migratory and have reduced paxillin tyrosine phosphorylation as compared to nonmetastatic LLC cells. In nonmetastatic Lewis lung carcinoma (LLC) tumor cells, inhibition of the serine/threonine protein phosphatase-2A (PP-2A) activity results in increased motility that is associated with a reduction in the phosphotyrosine content of paxillin. Studies to determine if PP-2A can regulate protein tyrosine phosphatase activity showed that blocking PP-2A activity of nonmetastatic LLC-C8 tumor cells with okadaic acid reduces protein tyrosine phosphatase activity. Among the tyrosine phosphatases whose activity was inhibited upon PP-2A inhibition is Shp-2. In contrast, protein levels of Shp-2 are unaffected by PP-2A inhibition. While these results do not fully identify how inhibition of PP-2A results in tyrosine dephosphorylation of paxillin, they do demonstrate that PP-2A can link serine/threonine and tyrosine signaling pathways by regulating protein tyrosine phosphatases. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sterigmatocystin induced apoptosis in human pulmonary cells in vitro

Sterigmatocystin (ST) is generally recognized as a potential carcinogen, mutagen and teratogen. Studies showed that ST could induce adenocarcinoma of lung in mice in vivo and DNA damage, cell cycle arrest in a human immortalized bronchial epithelial cell line (BEAS–2 B cells) and a human lung cancer cell line (A549 cells) in vitro. Besides, ST could induce G₂ arrest (cell cycle arrest in G₂ phase) in several other cells. Cell cycle arrest may be one of the common toxic effects of ST. As cells may undergo apoptosis or death due to cell cycle arrest, we wondered whether apoptosis is another common effect of ST in different cells in vitro. In the present study, we studied the effects of ST on proliferation and apoptosis in A549 cells and BEAS–2 B cells with 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay and flow cytometric analysis (FCM). The MTT results showed that proliferation inhibition following ST treatment for 24 h was observed in both A549 and BEAS–2 B cells in vitro. And increased apoptosis by FCM was also found after ST treatment. Down-regulation of Bcl-2, up-regulation of Bax and the activation of caspase-3 after ST treatment were detected by western blotting analyses. The results in the present study are consistent with our previous results, which indicated that inducing apoptosis may be a common effect of ST in different cells in vitro.     

The autoimmune-predisposing variant of lymphoid tyrosine phosphatase favors T helper 1 responses

The C1858T single nucleotide polymorphism in PTPN22, which is the gene encoding lymphoid tyrosine phosphatase (LYP), confers increased risk for various autoimmune disorders in Caucasians. Although the disease-associated LYP allele (LYP*W620) is a gain-of-function variant that has higher catalytic activity than the major allele (LYP*R620), it is still unclear how LYP*W620 predisposes for autoimmunity. Here, we compared both T cell signaling and T cell function in healthy human donors homozygous for either LYP*R620 or LYP*W620. Generally, the presence of LYP*W620 caused reduced proximal T cell antigen receptor-mediated signaling (e.g. ζ chain phosphorylation) but augmented CD28-associated signaling (e.g. AKT activation). Altered ligand binding properties of the two LYP variants could explain these findings since LYP*R620 interacted more strongly with the p85 subunit of PI3K. Variation in signaling between cells expressing either LYP*R620 or LYP*W620 also affected the differentiation of conventional CD4⁺ T cells. For example, LYP*W620 homozygous donors displayed exaggerated Th1 responses (e.g. IFNγ production) and reduced Th17 responses (e.g. IL-17 production). Importantly, while regulatory T cells normally suppressed Th1-mediated IFNγ production in LYP*R620 homozygous individuals, such suppression was lost in LYP*W620 homozygous individuals. Altogether, these findings provide a molecular and cellular explanation for the autoimmune phenotype associated with LYP*W620.     

HIV Tat蛋白增加CD4+ T淋巴细胞bcl-2表达并抑制TRAIL诱导的细胞凋亡

目的探讨HIV Tat蛋白对CD4^＋ T淋巴细胞bcl-2表达的影响，并探讨肿瘤坏死因子相关凋亡诱导配体（TRAIL）与经HIV Tat蛋白刺激后的CD4^＋ T淋巴细胞凋亡的相互关系。方法用Western blot方法测定经HIV Tat蛋白刺激后，CD4＋ T淋巴细胞表达bcl-2的水平，以λ-氨基放线菌素D（7-AAD）和AnnexinV染色方法测定CD4＋ T淋巴细胞的凋亡。结果HIV Tat蛋白能明显增加CD4＋ T淋巴细胞bcl-2的表达，以100ng/ml为最佳浓度；7-AAD染色结果表明100ng/ml重组TRAIL能诱导53．85％±2．63％的CD4^＋ T淋巴细胞发生凋亡，如CD4^＋ T淋巴细胞经HIV Tat蛋白刺激后，则仅有16．04％±5．26％的细胞发生凋亡，此作用能被多克隆抗-Tat蛋白抗体抑制。Annexin V染色取得了同样的结果。结论经HIV Tat蛋白刺激后CD4^＋ T淋巴细胞bcl-2的表达明显增加，并能抑制由重组TRAIL诱导的细胞凋亡，提示HIV Tat蛋白是导致HIV在CD4^＋ T淋巴细胞内持续感染的重要调节蛋白，在HIV感染中起十分重要作用。     

人FAT10蛋白过表达诱导饥饿状态下HEK 293细胞发生凋亡

目的:采用flag标记的人FAT10蛋白研究人FAT10蛋白对HEK293细胞的影响。方法:将FAT10基因片段克隆到载体pcDNA3-flag上,对阳性克隆进行PCR、酶切和测序鉴定,用脂质体转染HEK293细胞,用Western blotting方法检测外源性FAT10正常培养状态和饥饿状态下的HEK293细胞中的表达情况;并用XTT法和DNA ladder法观察正常培养和饥饿状态下HEK293细胞的凋亡情况。结果:重组质粒在HEK293细胞中高效表达,但在正常培养状态下和饥饿状态下表达情况不同。饥饿状态下,过表达FAT10的HEK293细胞存活率显著低于对照细胞,并且出现DNA ladder现象。结论:成功构建了带Flag标签的FAT10真核表达质粒,可在HEK293细胞中高效表达;FAT10过表达促进饥饿状态的HEK293细胞发生凋亡。     

The CD45 protein tyrosine phosphatase is required for the completion of the activation program leading to lymphokine production in the Jurkat human T cell line.

Stimulation of the T cell antigen receptor, TCR-CD3, induces tyrosine phosphorylation of specific cellular proteins through activation of a tyrosine kinase. The possible regulatory role of the CD45 protein tyrosine phosphatase in this process was explored by studying the functional properties of cellular variants of the Jurkat T cell line which have been selected to have normal levels of the TCR-CD3 complex, but low or negative expression of CD45. These variants had less than 20% of the normal membrane tyrosine phosphatase activity. Triggering the TCR-CD3 receptor on the CD45 variants with anti-CD3 mAb induced the activation of a tyrosine kinase. Tyrosine phosphorylation of cellular substrates as well as of the CD3 zeta chain was qualitatively comparable to normal cells although the extent of stimulation was lower. No differences were observed between the variants and the normal cells in the duration of the tyrosine phosphorylation signal. The increase in intracellular calcium concentration following receptor stimulation was also less efficient, suggesting that CD45 is necessary for optimal generation of the second messengers of the activation. The CD45 deficient cells secreted highly reduced levels of lymphokines (IL-2, IL-3 or GM-CSF) after activation by anti-CD3 mAb combined with the phorbol ester TPA. This impaired lymphokines production is related to the absence of CD45 since a CD45+ revertant subclone, isolated from one CD45- clone, produced normal levels of cytokines upon activation via CD3, while CD45- subclones were unable to secrete cytokines following activation via CD3. However, upon activation with Ca2+ ionophore and PMA, all CD45- (sub)clones secreted cytokines at levels comparable to those produced by CD45+ cells. These results show that CD45 is required for cytokine production after activation via the TCR-CD3 complex.