静注免疫球蛋白对新生儿单个核细胞IL—2,IL—4mRN …

探讨静注免疫蛋白抑制体外脐血Ｂ细胞免疫蛋白释放的机制。方法运用ＲＴ－ＰＣＲ法观察ＩＶＩＧ对体外新生儿单个核细胞分泌的ＩＬ＿２ｍＲＮＡ及ＩＬ－４ｍＲＮＡ表达的影响。结论ＩＶＩＧ对ＩＬ－２，ＩＬ－４两种细胞因子产生的抑制可能源于转录到分泌至胞外整个阶段任一时相上的抑制 。     

静脉注射免疫球蛋白对新生儿脐血单个核细胞活化增殖的影响

目的探讨静脉注射免疫球蛋白（ＩＶＩＧ）对新生儿单个核细胞活化增殖的影响。方法运用光学显微镜及３Ｈ－ＴｄＲ掺入法观察ＩＶＩＧ对脐血单个核细胞（ＣＢＭＣ）形态学的影响及对ＣＢＭＣ增殖的调节。结果ＩＶＩＧ使ＣＢＭＣ的母细胞化减少,细胞代谢的速度减慢。ＩＶＩＧ使ＣＢＭＣ的３Ｈ－ＴｄＲ掺入率下降更加明显地反映了ＩＶＩＧ对ＣＢＭＣ增殖的抑制。ＩＬ－２或ＩＬ－２联合ＩＬ－４可以拮抗ＩＶＩＧ对ＣＢＭＣ增殖的抑制。结论ＩＶＩＧ并非直接抑制ＣＢＭＣ的活化或干预由ＩＬ－２与ＩＬ－２Ｒ相互作用所介导的增殖反应。ＩＶＩＧ可能通过抑制细胞因子的产生而阻碍ＣＢＭＣ的增殖反应     

定量测定IL—4和IFN—γmRNA的RT—竞争PCR法及其 …

目的 建立测定ＩＦＮ－γｍＲＮＡ和ＩＬ－ｍＲＮＡ和ＲＴ－竞争ＰＣＲ方法，探讨体外诱生条件并作临床初步应用。方法 用自行设计和制备的ＩＦＮ－γ ＣＤＮＡ和ＩＬ－４ ｅＤＮＡ竞争模板，作ＲＴ－竞争ＰＣＲ，对健康人经ＰＭＡ和ｃａｌｃｉｕｍ ｉｏｎｏｐｈｏｒｅ（钙离子载体）诱导的ＰＢＭＣ、１１例健康人和１３例哮喘患者ＰＢＭＣ作ＩＦＮ－γ ｍＲＮＡ和ＩＬ－４ ｍＲＮＡ定量测定。结果 在建立了准确的定量测定ｍ     

人可溶性IL-6R基因在COS7细胞中的表达及活性分析

目的在ＣＯＳ７细胞中表达具有生物学功能的人可溶性ＩＬ－６Ｒ（ｓＩＬ－６Ｒ），作为研究ｓＩＬ－６Ｒ结构与功能关系的基础。方法首先利用ＰＣＲ技术扩增出人可溶性ＩＬ－６Ｒ（ｈｓＩＬ－６Ｒ）编码基因片段，并重组入克隆载体ｐＡＬＴＥＲ－１。通过基因序列分析确定了目的基因的核苷酸序列，并进一步构建了由ＳＶ４０晚期启动子和ＨＣＭＶ早期启动子控制的表达质粒ｐＳＶＬ６Ｒ和ｐＣＭＶ６Ｒ。用脂质体介导的方法将表达质粒转染ＣＯＳ７细胞，并分别在ｍＲＮＡ水平（斑点杂交）和蛋白水平（ＥＬＩＳＡ和Ｗｅｓｔｅｒｎ－ｂｌｏｔ）检测ｓＩＬ－６Ｒ基因在ＣＯＳ７细胞中的表达。在７ＴＤ１，ＬＴ１２两种ＩＬ－６反应细胞系上检测转染细胞上清（含ｓＩＬ－６Ｒ）的生物学活性。结果在ｍＲＮＡ水平和蛋白水平分别检测到ｓＩＬ－６Ｒ基因在ＣＯＳ７细胞中的表达，表达产物分子量约为５００００。表达产物在７ＴＤ１，ＬＴ１２细胞系上检测到明显的生物学活性。结论天然ｓＩＬ－６Ｒ基因在ＣＯＳ７细胞中的成功表达为进一步制备ｓＩＬ－６Ｒ突变体及其结构与功能关系的研究奠定了基础     

IFN—γ调节HHV—6诱导单核细胞产生IL—10和IL—12

为探讨人疱疹病毒６型（ＨＨＶ－６）感染对单核／巨噬细胞功能的影响，用逆转录－聚合酶链反应（ＲＴ－ＰＣＲ）和双抗体夹心ＥＬＩＳＡ法检测ＩＬ－１０及ＩＬ－１２的产生。ＨＨＶ－６诱导单核细胞、ＴＨＰ－１细胞表达及产生ＩＬ－１０和ＩＬ－１２。细胞因子ｍＲＮＡ动力学观察显示ＩＬ－１２随ＩＬ－１０ｍＲＮＡ积累而减少，用抗人ＩＬ－１０的单克隆抗体阻断ＨＨＶ－６诱导的内源性ＩＬ－１０，ＩＬ－１２ｍＲＮＡ表达和因子产生明显增加，提示内源性ＩＬ－１０抑制ＩＬ－１２产生。在ＨＨＶ－６感染培养中加入ＩＦＮ－γ，ＩＬ－１２基因表达随ＩＦＮ－γ浓度而增加，ＩＬ－１０ｍＲＮＡ测减少，ＩＬ－１２和ＩＬ－１０因子测定结果亦明显增加或降低，表明ＩＦＮ－γ在转录水平调节ＨＨＶ－６诱导的ＩＬ－１２和ＩＬ－１０产生，其机理可能主要与ＩＦＮ－γ抑制内源性ＩＬ－１０有关。     

分泌抗rHuIL—6McAb杂交瘤细胞系的建立及其应用研究

应用常规方法建立了４株稳定分泌抗重组人ＩＬ－６（ｒＨｕＩＬ－６）单克隆抗体（ＭｃＡｂ）小鼠杂交瘤细胞系１Ｈ３、２Ａ１０、３Ａ３和４Ｂ１。其中，１Ｈ３为ＩｇＧ２ｂ（Ｋ），２Ａ１０为ＩｇＧ１（Ｋ），３Ａ３和４Ｂ１为ＩｇＧ２ａ（Ｋ）。４株ＭｃＡｂ特异性强，与细胞因子ＩＬ－１β、ＩＬ－３、ＩＬ－８、ＴＮＦ－α、ＧＭ－ＳＣＦ、ＩＣＡＭ－１，以及受体菌菌体蛋白成分均无交叉反应。间接ＥＬＩＳＡ测定小鼠腹水ＭｃＡ     

IL-4对治疗前后亚急性重型病毒性肝炎患者PBMCs TNF-α和IL-1αmRNA表达的影响

目的　了解白介素（ＩＬ）４ 对重型病毒性肝炎患者外周血单个核细胞（ＰＢＭＣｓ） 中肿瘤坏死因子（ＴＮＦ）α和ＩＬ１αｍＲＮＡ的表达的影响。方法　ＴＮＦα和ＩＬ１αｍＲＮＡ的表达水平采用半定量逆转录聚合酶链反应（ＲＴＰＣＲ） 进行检测。结果　ＩＬ４ 均以剂量依赖的方式抑制治疗前、后亚急性重型肝炎患者ＰＢＭＣｓ ＴＮＦα和ＩＬ１αｍＲＮＡ的表达,在发病初期,ＩＬ４ 于１ ０００Ｕｍｌ 时接近最大抑制效应;而恢复期患者,ＩＬ４ 于１００Ｕｍｌ 时即接近最大抑制效应,剂量－ 反应曲线明显左移。如以１００Ｕｍｌ 的ＩＬ４ 处理ＰＢＭＣｓ,恢复期亚急性重型肝炎患者ＰＢＭＣｓ ＴＮＦα和ＩＬ１αｍＲＮＡ的抑制率接近５０％ 。另外还发现,在发病初期,ＩＬ４ 对内毒素血症和ＨＢｅＡｇ 阳性患者ＰＢＭＣｓＴＮＦα和ＩＬ１αｍＲＮＡ表达的抑制作用低于阴性的患者。结论　ＩＬ４ 对发病初期患者ＰＢＭＣＴＮＦα和ＩＬ１αｍＲＮＡ 表达的抑制作用明显低于恢复期患者,其原因可能与内毒素血症和病毒血症有关     

内源性IL-12决定人PBMC产生干扰素γ的水平(英)

目的：ＩＦＮ－γ是由被有丝分裂原或抗原所激活的Ｔ细胞和ＮＫ细胞所产生，它具有广泛的免疫调节活性，现认为ＩＬ－１２（外源性）是诱导 ＩＦＮ－γ产生的强诱导剂，并可促进静息 ＣＤ４＋Ｔ细胞朝向 Ｔｈ１表型分化，即诱导细胞免疫。目的是为了解由ＰＢＭＣ产生的内源性ＩＬ－１２是否在体外可诱导ＩＦＮ－γ的产生及通过何机制诱导细胞免疫。方法：用抗ＣＤ３抗体、ＰＨＡ、抗ＣＤ３抗体加抗ＣＤ２８抗体和抗原（ＭＬＣ）来检测被刺激的ＰＢＭ细胞的ＩＦＮ－γ的产生，同时也用ＩＬ－１２和ＩＬ－１２Ｒβ１的中和抗体来抑制ＩＦＮ－γ的产生。结果：激活的人ＰＢＭ中ＩＦＮ－γ分泌依赖于内源性ＩＬ－１２的产生，而且激活的Ｔ细胞可诱导ＡＰＣ细胞产生ＩＬ－１２，此过程是通过Ｔ细胞表面的ＣＤ４０Ｌ和ＡＰＣ的ＣＤ４０相互作用而实现。结论：这些结果提示，内源性ＩＬ－１２在正常宿主抗细胞内抗原的感染反应中起重要作用，在某些形式的自身免疫性疾病和移植排斥反应的免疫病理发生中也起中心作用。     

IL—10对外周血单个核细胞体外产生IL—2及IFN—γ的调节作用

为探讨Ｔｈ１与Ｔｈ２两类细胞因子间相互调节，研究了ｒｈＩＬ－１０对ＰＨＡ体外诱导人ＰＢＭＣ产生ＩＬ－２及ＩＦＮ－γ的影响。结果表明，１０ｎｇ／ｍｌＩＬ－１０明显抑制ＰＢＭＣ产生ＩＬ－２及ＩＦＮ－γ（Ｐ＜０．０２及Ｐ＜０．０１）。在加入兔抗人ＩＬ－１０抗体的ＰＢＭＣ体外培养体系中，在５μｇ／ｍｌ浓度时，ＩＬ－２产生可明显增加（Ｐ＜０．０５），随着抗体浓度增加，ＩＬ－２呈剂量依赖性增加（ｒ＝０．９６２，Ｐ＜０．０１），ＩＦＮ－γ产生亦增加，但差异不明显。本研究表明ＩＬ－１０抑制活化人ＰＢＭＣ体外产生ＩＬ－２及ＩＦＮ－γ，而抗人ＩＬ－１０抗体则表现出增强作用。ＩＬ－１０介导Ｔｈ１与Ｔｈ２两类辅助性Ｔ细胞间的相互调节，选择机体对抗原的免疫应答类型，从而对临床疾患的防治有一定指导意义。     

重型病毒性肝炎患者PBMCs中TNF-α、IL-1α和IL-4mRNA表达水平及其意义探讨

本实验应用半定量ＲＴ－ＰＣＲ检测了８例急重肝、１３例亚急重肝和１６例慢重肝患者ＰＢＭＣｓＴＮＦ－α、ＩＬ－１α和ＩＬ－４ｍＲＮＡ的表达水平并对其意义进行了探讨。结果表明，急重肝和亚急重肝患者ＰＢＭＣｓＴＮＦ－α和ＩＬ－１αｍＲＮＡ的表达水平较正常人明显增高，且与内毒素血症和病情轻重相关，而慢重肝仅ＴＮＦ－αｍＲＮＡ略增高，提示ＴＮＦ－α和ＩＬ－１α在急重肝和亚急重肝的发病机理中可能起重要的作用，而在慢重肝的作用可能不是主要的。虽然三型重型肝炎患者ＩＬ－４ｍＲＮＡ的表达水平与正常人比较无显著差异，但急重肝和亚急重肝患者ＩＬ－４ｍＲＮＡ／ＴＮＦ－αｍＲＮＡ和ＩＬ－４ｍＲＮＡ／ＩＬ－１αｍＲＮＡ的比值均明显低于正常人，表明急重肝和亚急重肝患者炎症细胞因子和抗炎症细胞因子调节网络严重失调，ＩＬ－４水平相对低下可能是急重肝和亚急重肝患者ＴＮＦ－α和ＩＬ－１α异常增高的原因之一。     

Human T cell activation: differential response to anti-CD28 as compared to anti-CD3 monoclonal antibodies

Monoclonal antibodies (mAb) against CD3 or CD28 in conjunction with the tumor promoter phorbol 12-myristate 13-acetate (PMA) induce interleukin 2 receptor (IL2R) expression, IL2 production and proliferation in resting T cells. Recent studies indicate that these two pathways are biochemically distinct. In this study T cell activation induced by PMA and anti-CD28 mAb 9.3 is compared to the effects of PMA plus anti-CD3 mAb (T3-II and 235) in the presence or absence of cyclosporin A (CsA), dibutyryladenosine 3':5' cyclic monophosphate (db-cAMP) or cholera toxin (CT). Proliferation of T cells stimulated with PMA plus mAb 9.3 is resistant to the inhibitory effects of CsA, db-cAMP and CT. Only at the highest dose did CsA have any effect on PMA plus mAb 9.3-induced T cell proliferation. Conversely, CsA, db-cAMP and CT inhibit PMA plus T3-II-induced T cell proliferation. mRNA analysis further demonstrates the similarities and the differences between the CD28 and CD3 activation pathways. Recently, T3-II was reported to induce tumor necrosis factor (TNF) and lymphotoxin (LT) mRNA synthesis in PMA-treated T cells. In this study mAb 9.3 is shown to substitute for T3-II in the induction of TNF and mRNA. However, the production of TNF and LT mRNA in PMA plus mAb 9.3-treated T cells is greater than that seen in PMA plus T3-II-treated cells. mRNA synthesis included by PMA plus T3-II is blocked by CsA. mRNA production in T cells activated with PMA plus mAb 9.3 is resistant to CsA. Similar results are noted with IL2 and IL2R mRNA. Flow cytometric analysis of the IL2R confirms the mRNA data. CsA blocks the T3-II-induced potentiation of PMA-induced IL2R expression but not the mAb 9.3-induced potentiation. This differential inhibitory effect of CsA on IL2R expression is also seen with db-cAMP and CT. We examined the effects of these two pathways on the expression of the early activation antigen EA 1 and cytoplasmic free calcium. Recently, we have shown anti-CD3 mAb potentiate EA 1 expression induced by 1,2-sn-dioctanoylglycerol and this potentiation is calcium dependent. dp-cAMP blocks T3-II- and 235-induced potentiation of EA1 expression and inhibits the T3-II- and 235-mediated rise in intracellular free calcium [( Ca2+]i). Conversely, 9.3 does not potentiate EA 1 expression or induce a rise in [Ca2+]i. These results provide further evidence that the CD28 and CD3 activation pathways utilize distinct signal transduction pathways.     

新生儿和成人PBMC中IL-4基因表达和NF-AT活性的比较

通过比较新生儿脐血单个核细胞 (CBMC)和成人外周血单个核细胞 (PBMC)中IL 4基因表达水平和活化T细胞核因子(NF AT)活性 ,探讨新生儿IL 4基因表达水平低下的机制。用ELISA和RT PCR法测IL 4及其mRNA水平 ;电泳迁移率转换试验 (EMSA)测NF AT活性。结果显示 :抗CD3+PMA刺激后 ,CBMC培养上清液中IL 4水平较PBMC明显低下 (P <0 0 1) ;CBMC产生的IL 4mRNA较PBMC明显减少 ;CBMC核蛋白内几乎测不出NF AT活性 ,而PBMC核蛋白内NF AT活性较强。表明在转录水平上缺乏NF AT调控可能使新生儿IL 4基因转录减少 ,从而导致新生儿IL 4基因表达水平低下。     

Induction of interleukin 2 (IL2) and interferon-γ and enhancement of IL2 receptor expression by a CD26 monoclonal antibody

The ability of the 134-2C2 monoclonal antibody (mAb; CD26) to transmit an activation signal and to affect T cell proliferation has been studied. The 134-2C2 mAb, although not being mitogenic by itself, is able to increase the proliferation of purified T cells in the presence of exogenous interleukin 2 (IL2) or phorbol 12-myristate 13-acetate (PMA). No effect of our mAb was observed on the proliferation of T cells induced by other stimuli such as Sepharose-bound CD3 mAb, phytohemagglutinin or calcium ionophore. Since the co-stimulatory effect of 134-2C2 mAb on PMA-induced T cell proliferation was strongly inhibited by an anti-Tac antibody, its involvement on the IL2/IL2 receptor pathway was investigated. An increased IL2 secretion in T cells cultured with PMA plus 134-2C2 mAb was observed and Northern blot analysis showed that the mAb 134-2C2 acts synergistically with PMA favoring the induction of both IL2 and interferon-γ mRNA synthesis, as well as the enhancement of IL2 receptor and transferrin receptor mRNA expression. Studies on mechanisms implicated in signal transduction showed that 134-2C2 mAb modifies neither intracellular calcium levels nor phosphoinositide breakdown. Additionally, no effect was exerted on protein kinase C translocation. These data suggest that the CD26 antigen is involved in T cell activation in an IL2/IL2 receptor-dependent pathway.     

Mechanism of ethanol-mediated immunosuppression in mice: ethanol suppresses T-cell proliferation without affecting IL2 production and IL2 receptor expression.

The effect of extended ethanol consumption in young C57BL/6 mice on T-cell proliferation was studied. Splenic cells of young mice (3-4 months old), fed with one of three different liquid diets (5% ethanol, maltose-substitute, or standard liquid diet) for 28-38 days were cultured with plant lectins to assess T-cell proliferation and IL2 production. Expression of T-cell subset markers (CD4+/CD8+) was also determined. Then, Con A-activated T blast cells were assessed for their ability to express IL2 receptor (IL2R) and to respond to IL2. Finally, the proliferative response of splenic cells to PMA/ionomycin was assessed. The results showed that both lectin- and PMA/ionomycin-induced mitogenesis and IL2-dependent proliferation of T-cells from ethanol diet-fed mice were diminished as compared with that of maltose-substitute diet or standard liquid diet. However, the ability of T-cells from ethanol diet-fed mice to produce IL2 and to express IL2 R or CD4+/CD8+ subset markers was not affected. Furthermore, the magnitude of ethanol-mediated suppression of T-cell proliferation induced by PMA/ionomycin was comparable with that induced by Con A. These results taken together indicate that ethanol suppresses T-cell proliferation by interfering with events following the IL2-IL2R interaction. Therefore, it is likely that ethanol inhibits murine T-cell proliferation by selectively affecting the progression (IL2R-mediated events) rather than the initiation (mitogenic receptor-mediated events) of the cell cycle.     

Effect of oestrogen on T cell apoptosis in patients with systemic lupus erythematosus

Defective control of T cell apoptosis is considered to be one of the pathogenetic mechanisms in systemic lupus erythematosus (SLE). Oestrogen has been known to predispose women to SLE and also to exacerbate activity of SLE; however, the role of oestrogen in the apoptosis of SLE T cells has not yet been documented. In this study, we investigated the direct effect of oestrogen on the activation‐induced cell death of T cells in SLE patients. The results demonstrated that oestradiol decreased the apoptosis of SLE T cells stimulated with phorbol 12‐myristate 13‐acetate (PMA) plus ionomycin in a dose‐dependent manner. In addition, oestradiol down‐regulated the expression of Fas ligand (FasL) in activated SLE T cells at the both protein and mRNA levels. In contrast, testosterone increased FasL expression dose‐dependently in SLE T cells stimulated with PMA plus ionomycin. The inhibitory effect of oestradiol on FasL expression was mediated through binding to its receptor, as co‐treatment of tamoxifen, an oestrogen receptor inhibitor, completely nullified the oestradiol‐induced decrease in FasL mRNA expression. Moreover, pre‐treatment of FasL‐transfected L5178Y cells with either oestradiol or anti‐FasL antibody inhibited significantly the apoptosis of Fas‐sensitive Hela cells when two types of cells were co‐cultured. These data suggest that oestrogen inhibits activation‐induced apoptosis of SLE T cells by down‐regulating the expression of FasL. Oestrogen inhibition of T cell apoptosis may allow for the persistence of autoreactive T cells, thereby exhibiting the detrimental action of oestrogen on SLE activity.     

Mechanism of immunosuppressive effect of alprazolam: alprazolam suppresses T-cell proliferation by selectively inhibiting the production of IL2 but not acquisition of IL2 receptor.

The purpose of this study was to elucidate the mechanism of action of alprazolam on concanavalin A (Con A)-induced murine T-cell proliferation. Splenic cells of BALB/c mice were first cultured with an optimum dose of Con A in the presence or absence of varying doses of alprazolam to assess effects of alprazolam on T-cell proliferation, interleukin 2 (IL2) production and IL2 receptor (IL2R) expression. Then, Con A-induced T-blast cells from BALB/c mice were cultured with an excess dose of human recombinant IL2 (rIL2) or crude rat IL2 supernate in the presence or absence of alprazolam to assess the effects of alprazolam on the interaction of IL2 and IL2R. The results of these studies clearly demonstrated that alprazolam can inhibit the T-cell proliferation in response to Con A but not to IL2. Alprazolam also reduced the production of IL2 by splenic T-cells, but did not alter the expression of IL2R on Con A-induced T-blast cells. Furthermore, the results also showed that (a) alprazolam did not inhibit the proliferative response of splenic T-cells to a combination of phorbol 12-myristate-13-acetate (PMA) and ionomycin, and (b) the addition of exogenous IL2 reversed the inhibitory effect of alprazolam on T-cell proliferation. Finally, the addition of alprazolam produced a time-dependent inhibiting effect on T-cell proliferation. However, this inhibitory effect of alprazolam was abolished when the drug was added to the cultures of competent cells that fully expressed IL2R. Taken together, these results suggest that alprazolam inhibits murine T-cell proliferation by affecting the mitogenic receptor-mediated events (initiation) rather than the IL2R-mediated events (progression) of ligand-activated T-cells through the cell cycle.     

Interleukin 4 (IL) 4 up-regulates gene and surface IL 1 receptor type I in murine T helper type 2 cells.

The T cell-derived cytokine interleukin (IL) 4 is known to increase the proliferative response of T cells stimulated with IL 1. IL 4 is also an autocrine growth factor for type II T helper cells (Th2) cells. In the present studies, we examined the effect of murine recombinant IL 4 on the expression of the IL 1 receptor type I (IL 1RtI) in murine Th2 cell lines at the mRNA and surface level. Using a specific anti-murine IL 1RtI monoclonal antibody and flow microfluorometry, we found that IL 4 increased the surface expression of IL 1RtI in a dose-dependent manner. In D10S cells, a subline of the Th2 cell line D10.G4.1, 50-500 pg/ml IL 4 up-regulated the receptor 1.8- to 3.2-fold (p less than 0.05). This up-regulation was also seen at the mRNA level. The effect was not due to increased stability of the mRNA, since IL 4 did not modify the half-life of IL 1RtI mRNA. IL 4 also up-regulated IL 1RtI on CDC25 cells, another Th2 cell line. However, we did not observe an effect of IL 4 on gene expression of IL 1RtI in BALB/c 3T3 fibroblasts. IL 2 and IL 4 showed an additive effect in up-regulating IL 1RtI and D10S cells. These studies indicate that IL 4 up-regulates IL 1RtI in murine Th2 cells by increasing gene expression for IL 1RtI without affecting mRNA stability. Thus, IL 4 production by Th2 cells may amplify the immune response via up-regulation of IL 1RtI.     

Differential inhibition of interleukin 2- and interleukin 4-mediated human B cell proliferation by ionomycin: a possible regulatory role for apoptosis

Surface immunoglobulin (Ig) cross-linking by anti-IgM (mu) antibodies leads to B cell activation resulting in numerous early biochemical events including an increase in intracellular [Ca2+]. Furthermore, anti-mu-activated B cells become able to proliferate in response to interleukin (IL)2 and IL4. These studies examined the effect of the calcium ionophore ionomycin, an enhancer of cytoplasmic [Ca2+] levels, on IL2 and IL4-mediated proliferation of anti-mu-stimulated normal human B cells. Ionomycin inhibited the proliferative response of anti-mu-activated B cells to IL4. In contrast, IL2 and phorbol 12,13 dibutyrate (PBu2)-mediated B cell proliferation was refractory to the growth inhibitory effects of ionomycin. In an attempt to delineate a possible mechanism(s) for this differential growth effect of ionomycin, we first studied direct effects of ionomycin on activated B cells. Our data suggested that ionomycin induced DNA fragmentation in anti-mu-costimulated B cells. Interestingly, in contrast to PBu2, IL4 did not prevent ionomycin-dependent DNA fragmentation. Importantly, H7, an inhibitor of protein kinase C activation, down-regulated only the IL2 and PBu2-driven B cell proliferation but not B cell proliferative response to IL4. These results suggest that putative protein kinase C activation, either by direct treatment with phorbol ester or during IL2 signaling, counteracts the inhibitory effects of ionomycin. In contrast, IL4 signaling does not exhibit the same protective properties.