Kahn M, Sugawara H, McGowan P, Okuno K, Nagoya S, Hellström K E, Hellström I, Greenberg P
Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, WA 98121.
J Immunol. 1991 May 1;146(9):3235-41.
p97 is a human tumor-associated Ag present on most melanoma cells that represents a possible target for immunologic attack. To evaluate the capacity of T cells reactive with this protein to promote elimination of melanoma cells expressing p97, a murine model was developed by transfecting a C3H/HeN melanoma with the p97 cDNA, generating p97-specific CD4+ T cells by in vivo immunization of C3H/HeN mice with a vaccinia/p97 recombinant virus followed by in vitro cloning with soluble p97 protein, and determining whether these CD4+ T cells could mediate rejection of pulmonary metastases. Characterization of the T cell clones demonstrated the presence of both I-Ak and I-Ek-restricted clones, although the majority of clones recognized p97 in the context of I-Ek. Analysis of clonal specificity using truncated p97 proteins revealed that at least three epitopes were immunogenic, and further studies with overlapping 15-amino acid peptides from a region of the p97 molecule defined by these truncated proteins identified an immunodominant epitope responsible for the majority of the I-Ek response. The T cell clones were not capable of directly recognizing the p97-expressing melanoma cells but responded to the tumor if syngeneic APC were present to process the tumor-derived p97 Ag. The therapeutic efficacy of these CD4+ T cell clones was evaluated in an adoptive therapy model in which mice bearing metastatic pulmonary lesions were treated by i.v. administration of the p97-specific cells. Despite the inability of the CD4+ clones to directly respond to or lyse the tumor cells, the clones were effective in promoting tumor eradication. In vitro studies demonstrated that this may have reflected secretion of lymphokines that activated macrophages to lyse the tumor. The results suggest that noncytolytic p97-specific CD4+ T cell clones can be effective in therapy of pulmonary melanoma metastases. Moreover, if human T cells reactive with the p97 protein could be generated, the expression of this tumor-associated Ag in melanoma cells might be adequate for such T cells to mediate a therapeutic antitumor response.
p97是一种存在于大多数黑色素瘤细胞上的人类肿瘤相关抗原，是免疫攻击的一个可能靶点。为了评估与该蛋白反应的T细胞促进消除表达p97的黑色素瘤细胞的能力，构建了一个小鼠模型，方法是用p97 cDNA转染C3H/HeN黑色素瘤细胞，用痘苗/p97重组病毒对C3H/HeN小鼠进行体内免疫，然后用可溶性p97蛋白进行体外克隆，从而产生p97特异性CD4+ T细胞，并确定这些CD4+ T细胞是否能介导肺转移瘤的排斥反应。对T细胞克隆的特性分析表明，存在I-Ak和I-Ek限制性克隆，尽管大多数克隆在I-Ek背景下识别p97。使用截短的p97蛋白分析克隆特异性发现，至少有三个表位具有免疫原性，对来自这些截短蛋白所定义的p97分子区域的重叠15氨基酸肽进行的进一步研究确定了一个免疫显性表位，它介导了大部分I-Ek反应。T细胞克隆不能直接识别表达p97的黑色素瘤细胞，但如果有同基因抗原呈递细胞（APC）来处理肿瘤来源的p97抗原，T细胞就能对肿瘤作出反应。在一个过继性治疗模型中评估了这些CD4+ T细胞克隆的治疗效果，在该模型中，通过静脉注射p97特异性细胞来治疗患有转移性肺部病变的小鼠。尽管CD4+克隆不能直接对肿瘤细胞作出反应或裂解肿瘤细胞，但这些克隆在促进肿瘤根除方面是有效的。体外研究表明，这可能反映了淋巴细胞因子的分泌，这些因子激活巨噬细胞来裂解肿瘤。结果表明，非细胞溶解性的p97特异性CD4+ T细胞克隆在治疗肺黑色素瘤转移方面可能是有效的。此外，如果能够产生与p97蛋白反应的人类T细胞，黑色素瘤细胞中这种肿瘤相关抗原的表达可能足以使此类T细胞介导治疗性抗肿瘤反应。
