Abrams S I, Dobrzanski M J, Wells D T, Stanziale S F, Zaremba S, Masuelli L, Kantor J A, Schlom J, Masuelle L [corrected to Masuelli L ]
Laboratory of Tumor Immunology and Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-1750, USA.
Eur J Immunol. 1995 Sep;25(9):2588-97. doi: 10.1002/eji.1830250928.
Alterations in the ras p21 protein have been associated with both rodent and human neoplasia. Thus, mutated ras p21 proteins may bear unique antigenic epitopes for immune recognition, such as by T cells, which have been implicated in host antitumor activity. Synthetic peptides that mimic segments of mutated ras p21 have been reported to be immunogenic in mice in vivo, although detailed functional analyses remains undefined. Here, in a murine model, we explored and characterized distinct effector properties of host-derived T lymphocytes reactive to mutated ras peptides, which was consistent with the CD4+ T helper type 1 (Th1) subset. BALB/c mice (H-2d) were immunized with a purified peptide, 13 amino acids in length, containing the substitution of Gly (G12) to Val (V12) at position 12, which is commonly found in human carcinomas. An alpha beta T cell receptor-positive, CD3+, CD4+, CD8- T cell line was established, which expressed peptide-specific proliferation. Cytokine assays revealed the production of interleukin-2, interferon-gamma, tumor necrosis factor and granulocyte-macrophage colony-stimulating factor. Moreover, antigen-specific cytotoxicity was demonstrable against: (1) Iad-bearing A20 tumor cells incubated with exogenously bound V12 peptide; and (2) A20 tumor cells transduced with the K-ras p21 oncogene encoding the corresponding point mutation. CD4(+)-mediated cytotoxicity was major histocompatibility complex (MHC) class II-restricted, as revealed by the absence of lysis against MHC class II- P815 targets, inhibition of A20 lysis with anti-Iad monoclonal antibodies, and induction of lysis against L cell targets transfected with E alpha A beta d. Independent isolation of a second CD4+ V12 line revealed a very similar cytolytic and MHC class II-restricted profile. Overall, these data demonstrated that peptide immunization produced a CD4+ Th1 response that specifically recognized tumor cells expressing endogenous activated K-ras epitopes, which may have implications for the development of peptide-based active immunotherapies.
Ras p21蛋白的改变与啮齿动物和人类肿瘤形成均有关联。因此，突变的Ras p21蛋白可能带有独特的抗原表位以供免疫识别，比如被认为参与宿主抗肿瘤活性的T细胞识别。据报道，模拟突变Ras p21片段的合成肽在小鼠体内具有免疫原性，不过详细的功能分析仍不明确。在此，我们在一个小鼠模型中探究并表征了对突变Ras肽有反应的宿主来源T淋巴细胞的不同效应特性，这些特性与CD4+ 1型辅助性T细胞（Th1）亚群一致。用一种纯化的13个氨基酸长度的肽对BALB/c小鼠（H-2d）进行免疫，该肽在第12位含有常见于人类癌组织中的甘氨酸（G12）到缬氨酸（V12）的替换。建立了一个αβ T细胞受体阳性、CD3+、CD4+、CD8-的T细胞系，其表现出肽特异性增殖。细胞因子检测显示白细胞介素-2、干扰素-γ、肿瘤坏死因子和粒细胞-巨噬细胞集落刺激因子的产生。此外，抗原特异性细胞毒性可针对以下细胞表现出来：（1）与外源性结合的V12肽一起孵育的携带Iad的A20肿瘤细胞；（2）用编码相应点突变的K-ras p21癌基因转导的A20肿瘤细胞。如对MHC II类P815靶细胞无裂解、用抗Iad单克隆抗体抑制A20裂解以及对转染了EαAβd的L细胞靶细胞诱导裂解所显示，CD4(+)介导的细胞毒性受主要组织相容性复合体（MHC）II类限制。独立分离出的第二个CD4+ V12细胞系显示出非常相似的溶细胞和MHC II类限制特征。总体而言，这些数据表明肽免疫产生了一种CD4+ Th1反应，该反应特异性识别表达内源性活化K-ras表位的肿瘤细胞，这可能对基于肽的主动免疫疗法的开发具有启示意义。
