PI3K在TCR和CD28协同激发的γδT细胞活化信号转导中的作用

目的 探讨CD28协同结核杆菌（M.tb)低分子多肽激活人外周血γδ^ T细胞时，其胞内信号的传递经过磷酸肌醇3激酶（PI3K）的介导作用。方法 用激发型抗CD28单抗模拟第二信号，与M.tb抗原一起刺激纯化的T细胞，同时用特异性PI3K抑制剂LY294002阻断PI3K的活性，用流式细胞仪分析γδ^ T细胞上CD69分子的表达及γδ^ T细胞的增殖效应。结果 随着LY294002浓度的增加，γδ^ T细胞表面CD69分子的表达率降低，其增殖效应亦被不同程度地阻断。结论 抗CD28单抗可协同M.tb抗原激活γδ^ T细胞，綦知化信号在γδ^ T细胞内的转导经过PI3K的介导。     

HLA-E的表达对RSA及PIH患者外周血γδT细胞细胞毒效应的影响

探索HLA-E分子的表达对习惯性流产(recurrent spontaneous abortion,RSA)及妊高症(pregnancy-induced hypertension,PIH)患者外周血γδT细胞细胞毒效应的影响。通过固相抗体法体外分离并扩增外周γδT血细胞作为效应细胞,以HLA-E转染的LcL721.221细胞(.221E)及滋养层细胞JAR作为靶细胞,采用4 h乳酸脱氢酶(LDH)释放试验观察NK细胞对靶细胞的细胞毒效应。结果显示,来自RSA、PIH及正常对照组的γδ细胞均不能有效杀伤HLA-E转染的.221E细胞及JAR细胞,但未经HLA-E转染的LcL721.221细胞则被溶解;抗HLA-E单抗3D12及抗CD94单抗HP-3B1的阻断可以分别部分恢复效应细胞对靶细胞LcL721.221E的杀伤,但对JAR细胞没有影响;与正常对照组相比,RSA及PIH患者外周血γδT细胞对.221、.221E及JAR细胞的细胞毒活性没有显著性差异(P>0.05)。这说明HLA-E分子的体外表达可以保护靶细胞防止γδT细胞的杀伤,该保护机制主要是通过γδT细胞受体CD94/NKG2对靶细胞表面HLA-E分子的识别来实现的;滋养层细胞对γδT细胞杀伤的抵抗可能存在MHC I类非依赖的机制。     

辣椒素对人γδT细胞杀伤人骨肉瘤HOS细胞的影响

探讨辣椒素对人γδT细胞体外增殖及杀伤骨肉瘤细胞的影响及作用机制。分离健康人PBMC,加入到含异戊烯焦磷酸(isopentenyl pyrophosphate,IPP)和IL-2的DMEM-F12完全培养基中诱导培养γδT细胞。不同浓度的辣椒素作用于γδT细胞48h后,CCK-8法检测各药物浓度组γδT细胞的增殖能力,采用流式细胞术检测各组γδT细胞穿孔素、颗粒酶B、CD107a及IFN-γ的表达,用LDH释放法检测各组γδT细胞对骨肉瘤HOS细胞的体外杀伤活性。结果显示,培养7d时各组γδT细胞纯度达到了(85.33±6.07)%。浓度为3.2~50μmol/L的辣椒素能显著促进γδT细胞的增殖,在浓度为25μmol/L时其穿孔素、颗粒酶B、CD107a及IFN-γ的表达均显著高于对照组,且对人骨肉瘤HOS细胞的体外杀伤活性显著增强。以上结果提示辣椒素在体外能通过促进γδT细胞穿孔素、颗粒酶B和IFN-γ的表达上调显著增强其抗骨肉瘤细胞活性。     

Gardiquimod增强人γδT细胞杀伤肿瘤细胞的研究

目的研究Toll样受体7激动剂(Gardiquimod)对人γδT细胞杀伤肿瘤作用的影响。方法以异戊烯焦磷酸法扩增人外周血γδT细胞。用不同浓度的Gardiquimod处理γδT细胞和肺癌细胞A549,MTT法检测细胞增殖情况。LDH法检测Gardiquimod处理后γδT细胞对A549的杀伤活性;流式细胞术检测处理前后γδT细胞上CD107a、穿孔素和颗粒酶的表达情况。结果 Gardiquimod在5.0~0.31μg/ml浓度可明显促进γδT细胞增殖,同时抑制A549增殖。Gardiquimod处理γδT细胞后,杀伤A549能力明显增强,且CD107a、颗粒酶及穿孔素的表达显著升高,与对照组相比,有统计学差异(P<0.05)。结论 Gardiquimod通过增高γδT细胞上的CD107a、颗粒酶及穿孔素的表达来增强其杀伤肿瘤作用。     

急性髓细胞白血病患者外周血淋巴细胞亚群的特征及临床意义

目的通过检测急性髓细胞白血病患者外周血各淋巴细胞亚群的分布,探讨该类患者免疫功能状况。方法通过流式细胞术检测健康对照组(n=20)、急性髓细胞白血病初发患者(n=31)及完全缓解期患者(n=31)外周血中CD4+T细胞、CD8+T细胞、TCRγδ+T细胞、CD4+CD25+调节性T细胞(Treg)、CD16+CD56+NK细胞比例;通过细胞杀伤实验分析NK细胞和γδT细胞的杀伤活性以及与Treg的关系。结果与对照组相比,初发白血病患者和完全缓解患者外周血中CD4+T细胞、CD8+T细胞比例无明显差异,但CD4+CD25+Treg比例明显增高,TCRγδ+T细胞和CD16+CD56+NK细胞比例明显下降。初发病患者NK细胞和γδT细胞具有杀伤活性,但Treg能明显抑制其杀伤活性。结论急性髓细胞白血病患者外周血γδT和NK细胞虽具有杀伤功能,但比例明显下降,Treg对其杀伤功能具有抑制作用。     

一种简单快速的γδT细胞扩增方法

建立一种特异快速地诱导扩增人外周血γδT细胞的方法。用 5～ 10ml外周血通过CD3细胞的富集、γδ单抗的诱导以及肿瘤细胞刺激的培养体系进行γδT细胞的体外扩增。结果显示 ,γδT细胞能在短时间内快速大量扩增到 10 9～ 10 10 的数量级 ;诱导 4周的CD8、γδ阳性的细胞百分率分别为 42 6 9%和 5 8 6 7% ,明显高于诱导前的 2 3 97%和 6 6 2 % ;γδT细胞对NK敏感的K5 6 2细胞和NK抵抗的Daudi细胞均有较高的杀伤活性 ;γδT细胞对经抗HSP单抗封闭后的Daudi细胞的杀伤率明显下降。该培养体系是一种用血量少、特异、经济、快速的人外周血γδT细胞体外扩增方法。     

双氢青蒿素对γδT细胞杀伤SW1990细胞的增强作用

目的 探讨双氢青蒿素(dihydroartemisinin,DHA)对人外周血γδT细胞体外增殖及抗肿瘤活性的影响.方法 分离健康人外周血单个核细胞(PBMC),加入到含异戊烯焦磷酸(isopentenyl pyrophosphate,IPP)和IL-2的RPMI 1640完全培养基中诱导培养γδT细胞.不同浓度的DHA作用于γδT细胞4δ h后,MTT法检测各药物浓度组γδT细胞的增殖能力,采用流式细胞术检测各组γδT细胞穿孔素、颗粒酶B和CD107a的表达,用CCK-8试剂盒检测各组γδT细胞对SW1990细胞的体外杀伤效应.结果 培养8d时各组γδT细胞纯度达到了75.46％ ±5.32％.浓度为50～100μmol/ml的DHA能显著促进γδT细胞的增殖.DHA处理后γδT细胞杀伤胰腺癌SW1990细胞能力及其穿孔素、颗粒酶B和CD107a的表达均显著高于对照组.结论 DHA可增强γδT细胞抗肿瘤活性,其机制可能与其促进γδT细胞穿孔素和颗粒酶B的表达上调有关.     

白藜芦醇对γδT细胞杀伤结肠癌SW-1116细胞的影响及机制研究

目的 观察白藜芦醇作用前后γδT细胞对结肠癌SW-1116细胞杀伤活性的变化,并探讨其发生的机制。方法 异戊烯焦磷酸法体外扩增人外周血γδT细胞,不同浓度的白藜芦醇作用于γδT细胞和结肠癌SW-1116细胞,四甲基偶氮唑蓝(MTT)法检测白藜芦醇对γδT细胞及结肠癌细胞的生长的影响;流式细胞术(FCM)检测白藜芦醇作用前后γδT细胞穿孔素、颗粒酶B、CD107a的表达;乳酸脱氢酶( LDH)释放法检测白藜芦醇对γδT细胞杀伤结肠癌SW-1l16细胞活性的影响。Western blot检测药物作用前后γδT细胞细胞外信号调节激酶(ERK1/2)蛋白的活性的变化。结果 白藜芦醇在0.39 ～3.125μmol/L时对γδT细胞的生长具有促进作用,对结肠癌SW-1116细胞作用不明显;经白藜芦醇诱导后γδT细胞的穿孔素、颗粒酶B、CD107a的表达显著高于对照组(P＜0.05);对结肠癌SW-1116细胞的杀伤活性也显著高于未诱导组(P＜0.05);经浓度为0.1～10 μmol/L白藜芦醇作用的γδT细胞的p-ERK1/2表达较对照组增加(P＜0.05)。结论 白藜芦醇能够促进γδT细胞的增殖,并增强其对结肠癌SW-1116细胞的杀伤能力,其机制可能与上调γδT细胞表面的穿孔素、颗粒酶B、CD107a的表达及活化细胞外信号调节激酶等有关。     

CD4+ CD25+调节性T细胞对树突状细胞的杀伤作用

目的 探讨CD4^＋CD25^＋调节性T细胞是否对树突状细胞发挥免疫调节作用及其可能的机制。方法 用MACS（magnetic cell sorting）从BALB／c小鼠静息T细胞分离纯化CD4^＋CD25^＋T细胞，体外细胞增殖实验观察其对CD4^＋CD25^＋T细胞的免疫抑制作用；GM-CSF／IL-4培养自体小鼠骨髓来源DC，FACS（fluorescence-activated cell sorting）鉴定其表面分子特性；以CD3／CD28单克隆抗体活化CD4^＋CD25^＋调节性T细胞，FACS体外杀伤实验研究其对自体DC的调节作用，并观察穿孔素抑制剂EGTA对上述作用的影响。结果 用MACS法成功分离出CD4^＋CD25^＋T细胞，纯度可达98％，特异性表达而Faxp3基因，能明显抑制CD4^＋CD25^＋T细胞的体外增殖；骨髓来源的DC表达CDllc、MHCⅡ及少量协同刺激分子CD80、CD86；FACS体外杀伤实验证实以CD3／CD28抗体体外活化的CD4^＋CD25^＋调节性T细胞对自体DC有显著杀伤作用（P〈0．05），穿孔素抑制剂EGTA能部分抑制该杀伤效应（P〈0．05）。结论 CD4^＋CD25^＋调节性T细胞可通过杀伤作用对自体DC发挥免疫调节作用，穿孔素／颗粒酶杀伤途径可能参与其中。     

子宫内膜异位症患者γδ＋T细胞及NK细胞的功能分析

目的 分析子宫内膜异位症患者γδ＋T细胞和天然杀作细胞（NK）功能的变化,以及探讨患者腹腔液对正常人γδ＋T细胞细胞和自然杀伤细胞（NK）功能的影响。方法 采用免疫荧光细胞检测及细胞毒活性检测法,分析22例子宫内膜异位症患者外周血、腹腔液中γδ＋T细胞细胞及NK细胞的表型与功能。结果 子宫内膜异位症（疾病组）患者外周血、腹腔液中CD56^ 细胞与正常对照组相比较无明显差异,而疾病组腹腔液中的γδ＋T细胞及NK细胞的功能低于外周血及正常对照组。疾病组的腹腔液对正常人外周血γδ＋T细胞及NK细胞的功能具有负调节作用。结论 子宫内膜异位症患者的γδ＋T细胞及NK细胞的功能低下,处于被抑制状态,提示患者的腹腔液中,可能在γδ＋T细胞细胞及NK细胞的功能抑制因子。     

The CD94/NKG2C killer lectin-like receptor constitutes an alternative activation pathway for a subset of CD8+ T cells

The CD94/NKG2C killer lectin-like receptor (KLR) specific for HLA-E is coupled to the KARAP/DAP12 adapter in a subset of NK cells, triggering their effector functions. We have studied the distribution and function of this KLR in T lymphocytes. Like other NK cell receptors (NKR), CD94/NKG2C was predominantly expressed by a CD8(+) T cell subset, though TCRgammadelta(+) NKG2C(+) and rare CD4(+) NKG2C(+) cells were also detected in some individuals. Coculture with the 721.221 HLA class I-deficient lymphoma cell line transfected with HLA-E (.221-AEH) induced IL-2Ralpha expression in CD94/NKG2C+ NK cells and a minor subset of CD94/NKG2C(+) T cells, promoting their proliferation; moreover, a similar response was triggered upon selective engagement of CD94/NKG2C with a specific mAb. CD8(+) TCRalphabeta CD94/NKG2C(+) T cell clones, that displayed different combinations of KIR and CD85j receptors, expressed KARAP/DAP12 which was co-precipitated by an anti-CD94 mAb. Specific engagement of the KLR triggered cytotoxicity and cytokine production in CD94/NKG2C(+) T cell clones, inducing as well IL-2Ralpha expression and a proliferative response. Altogether these results support that CD94/NKG2C may constitute an alternative T cell activation pathway capable of driving the expansion and triggering the effector functions of a CTL subset.     

抗CD4单抗增强抗CD3单抗／IL—2活化的肿瘤特异性T细胞的抗瘤活性

目的探讨抗CD4mAb增强抗CD3mAb刺激的肿瘤特异性T细胞增殖和杀瘤活性的作用。方法将肿瘤细胞免疫的小鼠脾细胞,采用4种不同的方案培养1单独加2×104U/LrIL2IL2组2单独加抗CD3mAb抗CD3组3加抗CD3mAb48h后,再加入抗CD3mAb和2×104U/LrIL2抗CD3 IL2组4同时加抗CD3mAb和抗CD4mAb48h后,再加入抗CD3mAb、抗CD4mAb和2×104U/LrIL2抗CD3 IL2 抗CD4组。然后分别检测4组效应细胞的增殖水平、杀瘤活性及表型。结果抗CD3 IL2组细胞的3HTdR掺入量在第6,12和20d分别为:22045、13986和1931;抗CD3 IL2 抗CD4组细胞的3HTdR掺入量在第6、12和20d,分别为46193、31047和7443,后者明显高于前者P0.05。在培养12d时,抗CD3 IL2组的细胞对FBL3细胞株的最大杀伤率为83.6%;抗CD3 IL2 抗CD4组细胞的最大杀伤率为91.7%。细胞表型:FACS分析表明,抗CD3 IL2 抗CD4组培养12d的细胞,99%以上为Thy1.2 细胞,且CD4 、CD25 细胞的百分率均高于抗CD3 IL2组。结论抗CD4mAb对抗CD3mAb刺激、IL2诱导的肿瘤特异性T细胞的增殖和杀瘤活性具有增强作用。     

C-type lectin-like receptors in peptide-specific HLA class I-restricted cytotoxic T lymphocytes: differential expression and modulation of effector functions in clones sharing identical TCR structure and epitope specificity

C-type lectin-like inhibitory receptors are heterodimers consisting of CD94 and NKG2-A-B molecules expressed on NK cells and on a subset of activated T lymphocytes. Their inhibitory effects on NK cytotoxicity and on the NK-like activity of T cell clones have been demonstrated, but no data are currently available on antigen-specific class I-restricted cytotoxic T lymphocytes (CTL). We have generated a panel of HLA-A2.1-restricted CTL clones directed against a nonapeptide derived from a melanoma-associated antigen, dopachrome tautomerase (TRP-2). All clones were CD8⁺ and TCR α β⁺. About half of them expressed a CD94^bright phenotype, whereas the remaining were CD94^dim. Only the CD94^bright CTL expressed the NKG2-A-B gene, consistent with the expression of a C-type, lectin-like, inhibitory CD94/NKG2-A-B heterodimer. Both CD94^bright and CD94^dim clones appeared to require similar amounts of synthetic epitope sensitizing target cells. Addition of anti-CD94 mAb resulted in a significant increase of specific killing by CD94^bright, but not by CD94^dim clones in the presence of suboptimal concentrations of peptide, whereas, when optimal amounts were used, the mAb did not induce a significant modulation of the cytotoxicity. Antigen-induced inward [Ca²⁺]_i fluxes were unaffected, but an enhancement of TCR down-modulation could be observed in the presence of anti-CD94 mAb at high concentration of antigenic peptide. The analysis of the TCR-Vβ repertoire of the CTL clones by RT-PCR and immunofluorescence revealed that all clones regardless of CD94 phenotype shared Vβ22 expression. Most importantly, sequence analysis showed that they all expressed identical Vβ22 TCR rearranged with Jβ2.1 and Cβ2. Taken together, these data indicate that different expression of functionally active lectin-like inhibitory receptors can be detected in CTL clones sharing identical TCR sequence and peptide specificity.     

微波消融肝癌对小鼠细胞免疫的影响

目的：探讨不同温度微波消融肝癌对小鼠细 胞免疫的影响。方法：建立C57BL/6J小鼠Hepa 1-6肝癌皮下移植模型,分别采用45 ℃、50 ℃、55 ℃和60 ℃×180 s 的消融条件对肝癌进行微波消融。用流式细 胞仪分析外周血CD4＋、CD8＋ T细胞和NK细胞的比例，用LDH法测脾NK细胞和灭活的Hep a 1-6细胞活化的脾细胞毒T 淋巴细胞（CTL）的细胞毒活性。结果:50 ℃和55 ℃组消融后 21 d 外周血CD4＋、CD8＋ T细胞和NK细胞比例明显升高，60 ℃组 消融后 21 d 外周血NK比例明显升高，但消融后42 d与对照组相比均无明显差异。50 ℃和55 ℃组消融后 21 d 和42 d脾CTL和NK细胞毒活性均明显增强，且均明显强于同期45 ℃ 组。50 ℃和55 ℃组消融后 21 d 脾CTL细胞毒活性明显强于同期60 ℃组。结论:在一定消融温度条件下，肝癌微波消融能促进机体产生细胞免疫反应。     

p40, a novel surface molecule involved in the regulation of the non-major histocompatibility complex-restricted cytolytic activity in humans

Four monoclonal antibodies (mAb) termed NKTA255, NKTA72, 1F1 and 1B1 were selected on the basis of their ability to inhibit the cytolytic activity of natural killer (NK) cell clones against P815 target cells. These mAb selectively reacted with normal or tumor cells of hematopoietic origin and displayed a cellular distribution similar to that of CD45 or CD11a/CD18 antigens. Immunoprecipitation experiments showed that they reacted with molecules with an apparent molecular mass of 40 kDa under both reducing and nonreducing conditions (“p40” molecules), thus differing from CD45 or CD11a/CD18 antigens as well as from the “inhibitory” receptors for HLA class I molecules (i.e. p58, CD94 and NKB1 molecules). Double-immunofluorescence analysis of peripheral blood mononuclear cells allowed the identification of three distinct populations on the basis of the fluorescence intensity of cells stained with anti-p40 mAb. p40^bright cells were homogeneously HLA-DR-positive, p40^medium cells were HLA-DR-negative but co-expressed CD56 antigens, while p40^dull cells were all CD3⁺. Anti-p40 mAb strongly inhibited the lysis of K562 target cells, mediated by fresh NK cells, as well as the lysis of P815 target cells by NK or T cell clones. In addition, in redirected killing assays, anti-p40 mAb strongly reduced the anti-CD16 mAb-induced cytolytic activity of NK cell clones. On the contrary, they did not inhibit either the anti-CD3 or anti-T cell receptor mAb-mediated cytolytic activity of T cell clones or the lysis of allogeneic phytohemagglutinin blasts mediated by specific cytolytic T cell clones. The p40-induced inhibition of the NK cytotoxicity required optimal cross-linking, as anti-p40 mAb could inhibit the lysis of Fcγ receptor (FcγR)-positive but not of FcγR-negative target cells. In addition, (Fab')₂ fragments of anti-p40 mAb failed to inhibit the lysis of FcγR-positive target cells. In conclusion, p40 molecules represent a new type of inhibitory surface molecule that appears to play a general regulatory role in the NK-mediated cytolysis.     

Activation-induced NK cell death triggered by CD2 stimulation

Both T cells and natural killer (NK) cells express CD2, the target of an alternative activation pathway that induces the proliferation of both cell types. The mitogenic response to CD2 ligation requires the co-expression of CD3 : TCR in T cells and FcγRIII in NK cells, suggesting that these receptors are involved in transducing the response initiated by CD2. The ability of FcγRIII to trigger the activation-induced death of IL-2-primed NK cells led us to investigate the potential for CD2 to trigger activation-induced NK cell death. Our results reveal that the same anti-CD2 monoclonal antibodies (mAb) that activate freshly isolated NK cells induce apoptosis in IL-2-primed NK cells. CD2-induced apoptosis results in chromatin condensation, DNA fragmentation and cleavage of caspase-3. Activation-induced NK cell death triggered by CD2 ligation is extremely rapid (DNA fragmentation is first observed at 90 min) and it is not inhibited by neutralizing antibodies reactive with TNF-α or Fas ligand. Whereas mAb reactive with distinct CD2 epitopes (i.e. T11.1, T11.2, and T11.3) are required for activation-induced T cell death, mAb reactive with a single CD2 epitope are sufficient for activation-induced NK cell death. The ability of CD2, CD16, and CD94 to induce apoptosis in IL-2-primed lymphocytes suggests that cytokine priming changes the response to a signaling cascade that is common to each of these activation receptors.     

Tumor cell lysis by T cells distinct from NK cells and alloantigen-specific cytotoxic T cells

The generation and mechanism of tumor cell lysis by cytotoxic T cells derived from natural killer cell (NK) and allospecific cytotoxic T cell (CTL)-depleted precursors were examined. NK cells and the precursors of alloantigen-specific CTL were deleted from human peripheral blood lymphocytes by preincubation with L-leucyl-L-leucine methyl ester (Leu-Leu-OMe). Following phytohemagglutinin activation, CD3(+), CD4(+) or CD8(+), CD11b(-), CD16(-), and NKH1(-) killer cells capable of lysing a broad spectrum of tumor targets were generated. Cytolysis was not strictly lectin dependent as similar killer cells were generated by activating Leu-Leu-OMe-treated T cells with immobilized monoclonal antibodies to the CD3 molecular complex. The rate of tumor cell lysis by these mitogen-activated T cells was slower than that mediated by CD3(-) NK cells. Tumor cell lysis by mitogen-activated killers was inhibited by anti-CD3 but was not restricted by major histocompatibility complex antigen expression on target cells or by CD4/CD8 expression on effectors. Although similar to NK cells in susceptibility to anti-LFA-1 inhibition of killing, these mitogen-activated killer cells were more sensitive to the inhibitory effects of anti-CD2 than were CD3(-)-activated NK-like cells. Thus, tumor cell lysis by CD3(+) cytotoxic cells generated from Leu-Leu-OMe-treated lymphocytes appears to be mediated in part by mechanisms distinct from those employed by CD3(-) NK cells or antigen-specific CTL.     

Split peripheral tolerance: CD40 ligation blocks tolerance induction for CD8 T cells but not for CD4 T cells in response to intestinal antigens

The role of antigen-presenting cells in the balance between immunity and tolerance to intestinal antigens remains poorly understood. In this study, we examined whether CD40 ligation affects the induction of CD4 and CD8 T cell tolerance in response to intestinal antigens. We show that an agonistic anti-CD40 mAb treatment did not block the induction of OVA-specific CD4 T cell tolerance, whereas this approach enabled strong priming of OVA-specific cytotoxic T cells (CTL), preventing CTL tolerance to intestinal antigen. Such CTL priming was independent of CD4 T cell help but required B7 costimulation. Co-administration of anti-CD40 mAb increased the synthesis of IL-2 and the expression of CD25 by CD8 T cells, but neither IL-2 production nor CD25 expression by CD4 T cells was enhanced by anti-CD40 mAb. However, neutralization of TGF-beta together with addition of agonistic anti-CD40 mAb was able to reverse CD4 T cell tolerance. These findings suggest that the induction of tolerance versus immunity against intestinal antigens is determined by the status of the antigen-presenting cells and that signals via CD40 differently regulate the outcome of CD4 and CD8 T cells in vivo.     

CD2-CD48 interactions promote cytotoxic T lymphocyte induction and function: anti-CD2 and anti-CD48 antibodies impair cytokine synthesis, proliferation, target recognition/adhesion, and cytotoxicity.

The role of CD2 signaling in cytotoxic T lymphocyte (CTL) development was examined by stimulating mouse T cells with anti-CD3 monoclonal antibody (mAb) in the absence or presence of anti-CD2 mAb or anti-CD48 mAb or both. Induction of nonspecific CTL and interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) synthesis were impaired in the absence of CD2-CD48 interactions. Anti-CD2 mAb also inhibited activation-induced expression of the high-affinity IL-2 receptor (IL-2R). In contrast, IFN-gamma receptor (IFNGR) expression was increased in the presence of anti-CD2 mAb. Reduced cytotoxicity by CTL induced in the absence of CD2-CD48 interactions was associated with a diminished ability of CTL to conjugate with target cells and reduced expression of granzyme B and perforin. Anti-CD2 mAb did not affect expression of Fas ligand and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) by anti-CD3-activated T cells. Cytotoxic effector function and granzyme B and perforin expression were rescued when exogenous IL-2 and IFN-gamma were added in combination with anti-CD2 mAb to anti-CD3-activated T cells at initiation of culture. We conclude that CD2-CD48 interactions during T cell activation are critical for the synthesis of sufficient IL-2 and IFN-gamma to drive CD8(+) T cells to differentiate into functional cytotoxic effector cells.     

Biased activation of human T lymphocytes due to low extracellular pH is antagonized by B7/CD28 costimulation

As T cell response to tumor-associated antigens may be impaired by the acidic microenvironment typical of solid tumors, we assessed the effect of extracellular pH (pH(e)) on the activation and proliferation of human T lymphocytes and generation of the cytotoxic response. T lymphocytes stimulated with anti-CD3 mAb or PHA at low pH(e) were unable to secrete IL-2 and IFN-gamma and their ability to progress through the cell cycle was impaired. T lymphocytes also displayed up-regulation of IFN-gammaR2 chain and CTLA-4 expression, rendering them sensitive to negative regulatory signals. Agonistic mAb against CD28, but not against CD2, completely restored cytokine production and cell cycle progression, but down-regulated IFN-gammaR2 and CTLA-4 expression. The anti-CD28mAb rescued the CTL response of allogeneic anti-tumor cultures generated at low pH(e). Following anti-CD28 mAb treatment, T cells synthesized cyclooxygenase-2 (Cox-2) protein, which is involved in the early phases of T cell activation. This rescue of T cell activation was independent of the inducible 6-phosphofructo-2-kinase (iPFK-2) pathway, which stimulates proliferation in hypoxic and acidic conditions. The restoration of proliferative and cytotoxic T cell responses by CD28-triggering provides insight into the mechanisms by which B7 enhances the T cell anti-tumor response in vivo.