双功能抗体抗CD3/抗CD19介导T细胞对靶细胞的杀伤作用

背景与目的:双功能抗体有2个抗原结合臂,一方面具有肿瘤相关抗原,另一方面具有和免疫效应细胞表面分子标记结合的能力,并能有效地使效应细胞靶向杀火肿瘤细胞的作用.本实验探讨抗CD3/抗CD19双功能抗体介导T细胞杀伤靶细胞的作用.方法:利用非放射性荧光染料Calcein-AM进行抗体介导的体外特异性杀伤活性榆测,Ficoll-Hypaque法分离外周血淋巴细胞(peripheral blood lymphocyte,PBL),流式细胞术从中分选T淋巴细胞及CD4+T淋巴细胞和CD8+T淋巴细胞作为效应细胞.首先以Raji细胞为靶细胞,按不同效靶比,不同抗体浓度分组,以PBS、抗CD3scFv+、抗CD3scFv抗体及非相关抗体抗CD3/抗PGP为对照,另设CD19-K562细胞为非相关靶细胞组,比较双功能抗体介导特异性体外杀伤活性.取上述杀伤实验效靶比25:1,抗体浓度500 ng/mL各组,ELISA法比较激活的T细胞分泌IL-2的量,Real-time PcR法检测T细胞因子IL-3、IFN-γ、TNF-α激活后的表达变化.结果:体外介导T细胞杀伤靶细胞Raji的效果比对照组明显增强(P＜0.05),激活T细胞分泌IL-2、IL-3、IFN-γ及TNF-α的表达均明显高于对照组.结论:双功能抗体抗CD3/抗CD19在体外介导T细胞对靶细胞具有较强的杀伤作用.     

微型双功能抗体介导人T细胞杀伤耐药实体瘤细胞

目的 探讨抗P-糖蛋白（P-gP）／抗CD3微型双功能抗体介导人T细胞杀伤耐药实体瘤细胞的作用。方法 采用抗E-tag亲和层析柱分离纯化抗P-gp／抗CD3微型双功能抗体,十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）进行鉴定;采用^51Cr释放实验,测定抗P-gP／抗CD3微型双功能抗体介导的人T细胞体外靶向杀伤活性;采用多药耐药（MDR）细胞系KB／MDR、敏感KB细胞裸鼠移植瘤模型,测定该微型双功能抗体介导的体内靶向杀伤活性。结果 纯化的抗P-gp／抗CD3微型双功能抗体,在相对分子质量28000和26000处各有1条蛋白带。在抗P-gp／抗CD3微型双功能抗体存在的情况下,激活的T淋巴细胞能够裂解KB／MDR细胞,且随着效靶比的增高而增高。抗P-gp／抗CD3微型双功能抗体联合人T淋巴细胞能有效抑制KB／MDR细胞裸鼠移植瘤的生长,而对敏感KB细胞移植瘤的生长无抑制作用。结论 抗P-gP／抗CD3微型双功能抗体在体内外均能介导人T淋巴细胞杀伤表达P-gP抗原的KB／MDR细胞,是有望用于耐药实体瘤临床治疗的双特异性抗体。     

抗人CD3人/鼠嵌合抗体的表达及特性

将从HIT3a基因库分离克隆的功能性抗CD3轻重链可变区基因插入含有人k轻链及γ1重链恒定区基因的哺乳动物表达载体中，构建了抗CD3嵌合抗体基因,用Lipofectin将抗CD3人／鼠嵌合轻重链基因共转染SP2／0细胞表达，获得稳定传代和稳定表达抗CD3嵌合抗体的转染杂交瘤细胞株C-HIT3a，ELISA，免疫荧光和PCR实验证实嵌合抗体与原鼠CD3单抗有相同的特异性和亲和性。体外生物活性的初步分析表明嵌合抗体与鼠CD3单抗对人的PBMC细胞的增殖有相同类型的作用，高剂量抗体抑制人T细胞的增殖，低剂量显示明显的激活增殖作用，当与IL-2联合应用其激活增殖作用增加20倍。细胞毒实验表明嵌合CD3抗体或由该抗体介导的免疫活性细胞(CD3-AK)对多种肿瘤细胞有明显的杀伤活性，较单用IL-2或单用LAK细胞其杀伤活性增加25倍。     

嵌合抗CD20 Fab‘对B淋巴瘤细胞Raji细胞生长的影响

目的：研究嵌合抗CD20基因工程抗体Fab‘的抗肿瘤活性。方法：利用MTT法以及^3H掺入法测定嵌合抗CD20 Fab‘对Raji细胞生长的影响。结果：MTT法测定结果显示嵌合抗CD20 Fab‘对Raji细胞的生长具有抑制作用，抑制作用成剂量依赖性，其IC50为24ug/ml；嵌合抗CD20 Fab‘对^3H-TdR掺入Raji细胞无抑制作用，表明抗CD20 Fab‘不影响Raji细胞DNA的合成；但嵌合抗CD20 Fab‘抑制^3H-UdR掺入Raji细胞，表明嵌合抗CD20 Fab‘对Raji细胞RNA合成具有抑制作用，其抑制作用成剂量相关性。结论：嵌合抗CD20 Fab‘抑制Raji细胞生长，嵌合抗CD20 Fab‘具有较好的抗肿瘤活性。     

融合PE38 的抗CD70 纳米抗体免疫毒素的制备及其对肾透明细胞癌786-O细胞的杀伤作用

目的：构建靶向CD70 分子的重组免疫毒素，通过表达、纯化制备PE38 与抗CD70 纳米抗体重组蛋白，体外抗肿瘤实验探究重组蛋白是否对高表达CD70 分子的阳性肿瘤细胞具有杀伤活性。方法：通过基因工程手段，将CD70 纳米抗体Nb 2B3基因片段通过一个连接子与pET21a-PE38 基因片段相连，获得重组表达载体pET21a-Nb 2B3-PE38 并转入BL21（DE3）感受态细胞中进行表达、纯化与鉴定。用间接ELISA 及FACS法检测Nb 2B3-PE38 与CD70 分子的结合活性，MTT法检测Nb 2B3-PE38 对高表达CD70 分子的肾透明细胞癌786-O 细胞的体外杀伤活性，Annexin Ⅴ-FITC/PI 双染法检测Nb 2B3-PE38 对786-O 细胞凋亡的影响。结果：成功构建抗CD70纳米抗体重组免疫毒素Nb 2B3-PE38，纯化获得纯度>90%的重组蛋白，SDS-PAGE及WB检测结果表明目的蛋白正确表达，分子量为56 000。纯化后的Nb 2B3-PE38 能与重组CD70 抗原及786-O细胞表面的CD70 分子特异性结合；25 μg/mL Nb 2B3-PE38即对786-O细胞产生极显著的杀伤作用（P<0.001），并且促进786-O细胞的细胞凋亡（P<0.01），其杀伤效应强于阳性对照顺铂（P<0.01）。结论：成功制备了特异性靶向CD70 分子的免疫毒素Nb 2B3-PE38，其能够有效杀伤786-O细胞并诱导细胞凋亡且效果强于顺铂。     

抗CD3/抗TNP双功能抗体的制备及对胃癌细胞系的杀伤作用

:目的　以化学方法将抗CD3 及抗三硝基苯 (TNP)单克隆抗体交联为双功能抗体 ,研究此双功能抗体与任何TNP化的抗肿瘤单抗结合 ,介导对肿瘤细胞的杀伤作用。方法　分别纯化抗CD3 及抗TNP单克隆抗体 ,经二硫苏糖醇 (DTT)还原、偶联得到抗CD3 /抗TNP双抗。TNP化抗胃癌单抗PD4 、3H11与抗CD3 /抗TNP双抗介导人淋巴细胞对胃癌细胞系MGC80 3的细胞毒作用。结果　双抗与TNP化的单抗结合 ,介导效应细胞对靶细胞的杀伤率高于未TNP化单抗 ,并随着效靶比的提高而升高。结论　抗CD3 /抗TNP双抗能够与不同种类的TNP化单抗结合介导效应细胞杀伤靶细胞 ,有潜在的临床应用价值     

人CD3AK细胞杀伤人肺腺癌细胞的形态学观察

抗CD3抗体激活的杀伤细胞(CD3AK细胞)是一种新型的免疫效应细胞，与LAK细胞相比具有广谱、较高的杀伤活性及低IL-2依赖性的特点，因而受到重视。关于其杀伤机制的研究目前尚无明确报道。本研究把体外培养中贴壁状态的人肺腺癌细胞与用抗CD3单克隆抗体激活的人外周血来源的CD3AK细胞共同培养，电镜下观察了两种细胞的相互作用和靶细胞被杀伤的过程．藉此对CD3AK细胞杀伤肿瘤细胞的机制作一探讨。     

CD3AK细胞对恶性肿瘤患者细胞免疫功能的影响

目的：观察抗CD3单克隆抗体激活的杀伤细胞（CD3AK细胞）对恶性肿瘤患者细胞免疫功能的影响。方法：65例恶性肿瘤病人分为两组，实验组（CD3AK细胞＋化疗）35例，对照组（单纯化疗）30例，两组病人分别于治疗前及治疗后作外周血T细胞亚群和血清可溶性白细胞介素2受体（sIL-2R）水平测定。结果：恶性肿瘤病人细胞免疫功能均校正常人低，化疗病人辅以CD3AK细胞治疗后外周血CD3^ 、CD4^ T细胞及CD4^ /CD8^ 比值均明显升高，sIL-2R水平显著下降；对照组病人经化疗后CD3^ 、CD4^ T细胞与CD4^ /CD8^ 比值明显下降，sIL-2R水平也下降，但其下降幅度比CD3AK细胞治疗组小，两者比较有统计学意义（P＜0.05)。结论：CD3AK细胞能有效地提高化疗中恶性肿瘤患者的细胞免疫功能。     

脐血CD34^＋细胞体外扩增及树突状细胞诱导的实验研究

目的 研究脐血CD34^＋细胞在体外经造血细胞生长因子扩增后,诱导树突状细胞（DC）并观察该类DC在抗肿瘤免疫中的作用。方法 Ficoll分离脐血单个核细胞,免疫微磁珠法分离纯化CD34^ 细胞,以干细胞因子、flt3配体、白细胞介素－3和红细胞生成素体外扩增2周,诱导DC生成,观察肿瘤抗原负载后诱导特异性细胞毒T淋巴细胞生成和对肿瘤细胞杀伤作用。结果（1）脐血经免疫微磁珠法分离可获得高纯高的CD34^ 细胞;（2）2周体外扩增后,细胞数显著增加达150倍;体外集落试验证实该类细胞可形成粒单细胞集落形成单位／（CFU－GM）;（3）扩增的细胞可成功诱导成DC,并具有活化异体淋巴细胞的功能,负载肿瘤抗原后能诱导发生肿瘤特异性淋巴细胞,并可特异性杀伤Daudi肿瘤细胞。结论 脐血来源CD34^ 细胞在体外能成功地扩增,并诱导产生功能性DC。     

抗CD3/抗CD19微型双功能抗体的构建、表达及活性测定

背景与目的:微型双功能抗体是基因工程抗体的-种形式,它具有两个抗原结合位点,可选择性募集效应细胞到靶细胞周围,介导特异性杀伤作用.本实验构建抗CD3/抗CD19微型双功能抗体(diabody)载体,表达纯化后测定其生物学活性.方法:用重叠PCR(overlap PCR)和PCR方法,构建抗CD3/抗CD19 diabody 载体,转化感受态大肠埃希菌进行原核表达.表达产物经抗His-tag亲和层析柱分离纯化,12%SDS-PAGE电泳及Western blot鉴定.应用间接免疫荧光和竞争性免疫荧光结合流式细胞分析技术(PACS)检测生物学活性.结果:基因重组质粒经测序证实序列正确.抗CD3/抗CD19 diabody能够在原核表达系统中进行可溶性表达.12%SDS-PAGE显示28×103和26×103各有-条带,Western blot在28×103显示有条带,与预期相符.表达产物经纯化定量可达5 mg/L.FACS检测抗CD3/抗CD19 diabody可与CD19+ Raji细胞和CD3+ Jurkat细胞特异结合,并能竞争性抑制HIT3a和HIT19a与上述细胞的结合活性.结论:本实验成功构建了抗CD3/抗CD19 diabody,并且能够进行可溶性表达,可与CD19+ Raji细胞和CD3+ Jurkat细胞特异结合,为以后的抗体功能实验奠定了基础.     

Potential therapeutic strategy for non-Hodgkin lymphoma by anti-CD20scFvFc/CD28/CD3zeta gene tranfected T cells

Background

Anti-CD20 monoclonal antibody treatment has not only increased survival and cure rates in many non-Hodgkin lymphomas, but also has prompted an explosion in the development of novel antibodies and biologically active substances with specific cellular targets in the field of malignancies treatment. Since the robust immune responses are elicited by the gene-modified T cells, gene based T cell therapy may also provide a powerful tool for cancer immunotherapy.

Methods

In this study, we developed a vector construction encoding a chimeric T cell receptor that recognizes the CD20 antigen and delivers co-stimulatory signals to achieve T cell activation. One non-Hodgkin lymphoma cell line Raji cells co-cultured with peripheral blood-derived T cells were stably transfected with anti-CD20scFvFc/CD28/CD3zeta gene or anti-CD20scFvFc gene. T cells expressing anti-CD20scFvFc/CD28/CD3zeta or anti-CD20scFvFc gene co-cultured with CD20 positive Raji cells for different times. Cell lysis assay was carried by [³H]TdR release assay. The expressions of Fas, Bcl-2 and Caspase-3 of Raji cells were detected by flow cytometric. The secretion of IFN-gamma and IL-2 in co-culture medium was tested by ELISA assay. Activity of AP-1 was analyzed by EMSA.

Results

Following efficient transduction of peripheral blood-derived T cells with anti-CD20scFvFc/CD28/CD3zeta gene, an obvious cell lysis of Raji cells was observed in co-culture. T cells transduced anti-CD20scFvFc/CD28/CD3zeta gene had superior secretion of IFN-gamma and IL-2 compared to T cells transduced anti-CD20scFvFc gene. Also it led to a much stronger Fas-induced apoptosis signaling transduction in target cancer cells.

Conclusion

So adoptively T cells transduced anti-CD20scFvFc/CD28/CD3zeta gene mediates enhanced anti-tumor activities against CD20 positive tumor cells, suggesting a potential of gene-based immunotherapy for non-Hodgkin lymphoma.     

Human gamma delta T cells recognize heat shock protein-60 on oral tumor cells

In the present investigations, gammadelta T cells were isolated from the peripheral blood of oral cancer patients and analyzed for their immunophenotype and cytotoxic potential. Flow-cytometric analysis revealed a dominant population expressing Vgamma9 and Vdelta2 T-cell receptors. In a 4-hr 51Cr-release assay, activated gammadelta T cells showed specific cytotoxicity against Daudi Burkitt's lymphoma cells and fresh oral tumor cells. Cold target competition assays demonstrated that gammadelta T cells recognize a common ligand on Daudi and oral tumor cells. Expression of heat shock protein 60 (hsp60) molecules was detected on the surface of Daudi as well as oral tumor cells by flow cytometry and immunoprecipitation of surface biotinylated cells by anti-hsp60 monoclonal antibody (MAb). Such MAbs brought about a significant inhibition of cytotoxicity of gammadelta T cells against Daudi and oral tumor cells. The results suggest that gammadelta T cells isolated from the peripheral blood of oral cancer patients have the ability to lyse oral tumor cells. The lysis of oral tumor cells occurs via recognition of hsp60 on the surface of oral tumor cells.     

Enhanced in vitro lysis of human ovarian carcinomas with activated peripheral blood lymphocytes and bifunctional immune heteroaggregates

Heteroaggregated monoclonal antibodies (HA) comprised of an anti-CD3 and an anti-tumor associated antigen (TAA) antibody were evaluated for their ability to lyse fresh human ovarian cancer cells. HAs were able to significantly enhance the in vitro lysis of fresh ovarian tumor cells by in vitro activated peripheral blood lymphocytes (PBLs). HAs did not increase tumor lysis using fresh PBLs or PBLs cultured overnight in vitro. HA efficacy required both anti-CD3 and anti-TAA antibodies to be present in the same molecule, implying that physical bridging between the effector and target cell by the HA may be a requirement for their activity in cell lysis. The presence of anti-CD3 antibody in the PBL cultures enhanced cell growth and did not block the efficacy of the anti-CD3 containing HAs. The frequent expression of multiple TAAs in human ovarian cancers and the ability to recruit cytotoxic T-cell activity with HAs in vitro give promise to the future of this form of immunotherapy in the clinical setting.     

Induction of tumor-cell lysis by bi-specific antibody recognizing ganglioside GD2 and T-cell antigen CD3

Human tumor cells expressing ganglioside GD2 were lysed by various effector populations targeted with an anti-CD3-anti-GD2 bi-specific antibody (BAb CD3 x GD2). This antibodyheteroconjugate was prepared by chemically cross-linking the OKT-3 monoclonal antibody (MAb) reactive with CD3 antigen on T lymphocytes with the ganglioside MAb ME 361, which binds preferentially to the tumor-associated ganglioside GD2. The specificity of target-cell lysis by the cytotoxic T cells (CTL) was mediated by the specificity of the targeting antibody: GD2-negative cells were not lysed in the presence of the CD3 x GD2 BAb. A dose-dependent response was observed in a range of 10 to 10,000 ng/ml. In contrast, 2 other BAbs recognizing the tumor-associated antigens EGF-R and TKB-2 had greater potency to mediate tumor-cell lysis than the GD2 x CD3 BAb. Peripheral-blood cells (PBL) stimulated with OKT-3 MAb or with irradiated tumor cells in a mixed lymphocyte culture (MLTC) could be induced to lyse GD2-positive tumor cells in the presence of CD3 x GD2 BAb. The tumor-cell lysis could be mediated by autologous or allogeneic effector cells. NK cells had no influence on the BAb-induced cytotoxicity.     

Bispecific CD3 × CD19 diabody for T cell-mediated lysis of malignant human B cells

For the treatment of minimal residual disease in patients with leukemias and malignant lymphomas, we constructed a heterodimeric diabody specific for human CD19 on B cells and CD3ϵ chain of the T cell receptor complex. The bispecific diabody was expressed in Escherichia coli using a vector containing a dicistronic operon for co-secretion of V_H3-V_L19 and V_H19-V_L3 single-chain Fv fragments (scFv). It was purified in one step by immobilized metal affinity chromatography (IMAC) from the periplasmic extract and culture medium. Flow cytometry experiments revealed specific interactions of the diabody with both CD3 and CD19 positive cells, to which it bound with affinities close to those of the parental scFvs. It was less stable than anti-CD3 scFv but more stable than anti-CD19 scFv when incubated in human serum at 37°C. In cytotoxicity tests, the diabody proved to be a potent agent for retargeting peripheral blood lymphocytes to lyse tumor cells expressing the CD19 antigen. The efficiency of cell lysis compared favorably with that obtained with a bispecific antibody (BsAb) of the same dual specificity that was prepared by the quadroma technique. Int. J. Cancer 77:763–772, 1998. © 1998 Wiley-Liss, Inc.     

Efficient inhibition of human B-cell lymphoma xenografts with an anti-CD20 x anti-CD3 bispecific diabody.

Bispecific antibodies have been exploited both as cancer immunodiagnostics and as cancer therapeutics, and have shown promise in several clinical trials in cancer imaging and therapy. A number of bispecific antibodies against B-cell markers have been shown to be effective in vitro in mediating tumor cell lysis and in vivo in inhibiting tumor growth in animal models. We have constructed a bispecific diabody from the variable genes encoding two hybridoma-derived monoclonal antibodies directed against human CD20 on B cells and CD3 on T cells. The anti-CD20 x anti-CD3 diabody was expressed in a single Escherichia coli host and purified by a one-step affinity chromatography. The bispecific diabody bound as efficiently to both CD20- and CD3-positive cells as the respective parental antibodies, and was capable of cross-linking CD20-positive tumor cells and human T lymphocytes as shown by cellular rosetting. The diabody effectively lysed human B-lymphoma cells in the presence of T-enriched human peripheral blood lymphocytes (PBL). Further, when combined with human PBL and interleukin-2, the diabody significantly prolonged the survival of nude mice inoculated with human B-lymphoma cells. Taken together, our results suggest that an anti-CD20 x anti-CD3 diabody may have significant clinical application in the treatment of human CD20-positive B-cell malignancies.     

激发型CD40单克隆抗体联合特异性细胞毒T淋巴细胞对B细胞淋巴瘤的免疫治疗作用

目的研究激发型CD40单克隆抗体5C11联合特异性细胞毒T淋巴细胞(CTL)对B细胞淋巴瘤的免疫治疗作用,方法人B细胞淋巴瘤Daudi细胞株经5C11刺激24或48 h,Annexin V/PI结合实验测定凋亡率,流式细胞术检测Fas表达率外周血单个核细胞来源的树突状细胞(DC),经凋亡Daudi细胞负载、5C11诱导成熟后,与自体T细胞混合培养,激发特异性CTL,JAM法检测5C11、CTL或5C11联合CTL对Daudi细胞的杀伤效应。皮下注射Daudi细胞,建立人源化SCID小鼠B细胞淋巴瘤模型;接种肿瘤细胞1周、3周后,分别经腹腔注射5C11、CTL、5C11 CTL进行治疗,通过肿瘤生长曲线、荷瘤小鼠生存期评价疗效。结果5C11作用后,Daudi细胞表面Fas的表达率显著上调,但细胞凋亡率没有明显改变。特异性CTL能有效杀伤靶细胞,且与5C11联合应用后,Daudi细胞DNA片段形成率显著增高,8 h为71.9%±4.0%,12 h达82.6%±4.4%经5C11、CTL、5C11联合CTL治疗后,荷瘤小鼠体内肿瘤生长速度均显著减缓,而且在低肿瘤负荷小鼠中,CTL、5C11联合CTL治疗分别取得了30.0%和70.0%的完全缓解率,与对照组相比,各治疗组小鼠生存期显著延长。结论激发型CD40单抗5C11可显著上调细胞表面Fas的表达,增强Daudi细胞对诱导凋亡的敏感性,从而促进肿瘤特异性CTL的体外杀伤和体内治疗效应。     

A bispecific recombinant immunotoxin, DT2219, targeting human CD19 and CD22 receptors in a mouse xenograft model of B-cell leukemia/lymphoma.

A novel bispecific single-chain fusion protein, DT2219, was assembled consisting of the catalytic and translocation domains of diphtheria toxin (DT(390)) fused to two repeating sFv subunits recognizing CD19 and CD22 and expressed in Escherichia coli. Problems with yield, purity, and aggregation in the refolding step were solved by incorporating a segment of human muscle aldolase and by using a sodium N-lauroyl-sarcosine detergent-based refolding procedure. Problems with reduced efficacy were addressed by combining the anti-CD19 and anti-CD22 on the same single-chain molecule. DT2219 had greater anticancer activity than monomeric or bivalent immunotoxins made with anti-CD19 and anti-CD22 sFv alone and it showed a higher level of binding to patient leukemia cells and to CD19(+)CD22(+) Daudi or Raji cells than did anti-CD19 and anti-CD22 parental monoclonal antibodies. The resulting DT2219, mutated to enhance its avidity, was cytotoxic to Daudi cells in vitro (IC(50) = 0.3 nmol/L). In vivo, DT2219 was effective in a flank tumor therapy model in which it significantly inhibited tumor growth (P < 0.05) and in a systemic model in which it significantly prolonged survival of severe combined immunodeficient mice with established Daudi (P < 0.008) compared with controls. DT2219 has broader reactivity in recognizing B-cell malignancies, has more killing power, and requires less toxin than using individual immunotoxin, which warrants further investigation as a new drug for treating B leukemia/lymphoma.     

MHC class-I-restricted auto-tumor-specific CD4+CD8- T-cell clones established from autologous mixed lymphocyte-tumor-cell culture (MLTC).

Autologous mixed lymphocyte-tumor cell cultures (MLTC) were initiated with cytokine (IFN gamma and TNF alpha)-treated ex-vivo tumor cells of lung, ovarian, breast and stomach carcinomas. The cytokine-treated tumors expressed class-I but not class-II molecules. Although the proportion of CD8+ lymphocytes increased in the bulk culture of MLTCs, in 5/7 experiments the majority of the established T-cell clones were CD4+. Among the CD8+ clones a high proportion (77%) was cytotoxic, while the proliferative response was more frequent among the CD4+ clones (70%). In 4/26 cytotoxic T-lymphocyte (CTL) clones (3/17 CD4+ and 1/9 CD8+), derived from a patient with class I+ class II- stomach carcinoma, lysis was restricted to the autologous tumor cells. These auto-tumor-specific clones did not lyse the autologous ConA blasts, the 5 allogeneic ex-vivo tumors, the NK-sensitive K562 or the relatively sensitive Daudi cells. The cytotoxicity of these clones was inhibited by pre-incubation of the tumor cells with W6/32 (alpha-class I) MAb, or by preincubation of the lymphocytes with OKT3 (alpha-CD3) MAb. The alpha-CD4 (OKT4) MAb had only a marginal effect on the CD4+ clones, while the lytic function of the CD8+ clone was inhibited by the alpha-CD8 (OKT8) MAb. The 3 CD4+ CTL clones also responded with proliferation to the autologous tumor cells. This proliferative response was inhibited by the presence of W6/32 MAb. Our results indicate that the auto-tumor lysis exerted by CD4+ CTL clones was restricted by the class-I antigens, and that the CD4 molecules of the clones were not essential for the lytic interaction.