负性刺激分子PD-L对T细胞介导小鼠L929肿瘤细胞免疫效应的影响

目的：探讨负性刺激分子在肿瘤细胞逃避免疫效应中的作用.方法：以L929细胞为靶细胞,体内致敏C57BL/6小鼠,注入PD-L1、PD-L2抗体阻断,并设立未致敏对照组.分离小鼠脾细胞,体外采用3H-TdR掺入法、荧光标记双染色FCM以及PI染色FCM法分别检测淋巴细胞增殖反应、活化诱导的细胞凋亡以及脾细胞及其培养上清对肿瘤细胞的杀伤效应.结果：L929细胞表达PD-L1,而不表达PD-L2.体内与体外联合应用PD-L1抗体,能显著增强L929肿瘤细胞诱导的致敏组小鼠脾细胞的增殖活性和特异性杀伤效应,并可抑制活化诱导的T细胞凋亡;PD-L1抗体亦可增加L929细胞诱导的未致敏组小鼠脾细胞的增殖活性和促进其脾细胞培养上清对L929细胞的杀伤效应.结论：PD-L1抗体可通过阻断PD1/PDL途径促进初始T细胞和致敏T细胞介导的抗瘤效应.

The role of negative co-stimulation molecule PD-L in the T-cell immune response against murine tumor cell line L929

Objective:To investigate the possible roles of the negative co-stimulation molecule PD-L(ligand) in the T-cell mediated immune response against tumor.Methods:Flow cytometric analysis was used to examine murine tumor cell line L929 expresses PD-L(L1 and L2).Anti-PD-L blocking monoclonal antibodies combined with injection i.p.of irradiated L929 into C57BL/6 mice was employed to sensitize the T cells of the animals.2 weeks after sensitization,mice were sacrificed,and splenocytes were prepared to perform the examinations of T cell proliferation,cytotoxic T cells(CTL) activity,and apoptosis through in vitro coculture with L929 in the presence of blocking PD-L antibodies.Results:The expression of PD-L1 by L929 was detectable,whereas there was no expression of PD-L2 on these cells.Application of blocking antibody against PD-L1 or PD-L2 together with irradiated L929 cells in the process of in vivo sensitization as well as in vitro stimulation,it was shown that blockade of PD-L1 significantly enhanced the T cell proliferation induced by L929 cells and the CTL activity against L929,evidenced by the increased apoptosis and death rate of L929 cells.In control,blockade of PD-L2 had small effects on these terms.Conclusion:The negative co-stimulation molecule PD-L1 plays a role in the escape of tumor cells from host T-cell mediated tumor immunity.Therefore,blockade of PD-L1 has potential significance for tumor immunotherapy.