DEVELOPMENT OF IMMUNOTHERAPY To HEMATOLOGIC MALIGNANCIES

我们的目标是开发利用NKT细胞进行血液系统恶性肿瘤的免疫治疗。人类NKT细胞的配体是CD1d/糖脂复合体，它利用TCR中的Va24。与小鼠NKT细胞一样，人类NKT细胞中存在CD4-CD8-和CD4+亚群。在这个项目中，我们现在新确定了CD8+亚群。此外，我们还阐明了这些亚群之间的功能差异，特别是细胞因子产生谱的差异。我们在这里发现，人类T细胞肿瘤经常高水平表达CD1d，并且Va24NKT细胞对CD1d+T细胞肿瘤细胞具有抗肿瘤活性。糖脂α-半乳糖基神经酰胺(a-GalCer)可增强NKT细胞的体外抗肿瘤活性。因此，直接给予α-GalCer或通过α-GalCer体外扩增的NKT细胞可能是治疗T细胞肿瘤性疾病的潜在选择。为了进一步探讨这种可能性，我们建立了基于NKT细胞的体内抗肿瘤治疗模型。小鼠前体T细胞肿瘤细胞株EL-4仅微弱表达CD1d。我们将CD1d基因导入EL-4细胞，获得了不同程度高表达CD1d的细胞系。在体外，NKT对高水平表达CD1d的EL-4细胞具有较强的细胞毒作用。然后，将这些细胞系注射到同基因B57BL/6小鼠体内。我们发现，注射了表达高水平CD1d的EL-4系的小鼠存活时间更长，并且通过注射a-GalCer延长了小鼠的存活时间。这些结果表明，内源性NKT细胞通过CD1d相互作用抑制肿瘤生长。我们现在制定了一项使用NKT细胞进行T细胞白血病临床试验的方案。

We aimed at development of immunotherapy to hematological malignancies using NKT cells. Human NKT cells, ligands for which are CD1d/glycolipid complexes, utilize Va24 in TCR. As in mouse NKT cells, presence of CD4-CD8-and CD4+ subsets have been known in human NKT cells. In this project, we now newly identified the CD8+ subset. Moreover, we clarified the differences in the function among these subsets, particulaily the difference in the cytokine production profile.We here found that human T cell neoplasms frequently express CD1d at a high level and that Va24NKT cells show anti-tumor activity against the CD1d+ T cell neoplastic cells. A glycolipid, a-galactosyl ceramide (a-GalCer), enhanced the anti-tumor activity of NKT cells in vitro. Therefore, direct administration of a-GalCer or administration of NKT cells that are expanded in vitro by a-GalCer could be a potential therapeutic option for T cell neoplastic diseases.To further investigate such a possibility, we established an in vivo model for NKT cell-based anti-tumor therapy. A mouse precursor T cell tumor cell line, EL-4 expresses CD1d only at a weak level. We introduced CD1d cDNA into EL-4 and obtained cell lines overexpressing CD1d at various levels. In vitro, NKT-based cytotoxicity was stronger for EL-4 expressing CD1d at higher levels. Then, these cell lines were injected into syngenic B57BL/6 mice. We found that mice injected with EL-4 lines expressing higher levels of CD1d survived longer periods of time and that the survival time was extended by the administration of a-GalCer. These results indicate that endogenous NKT cells inhibit tumor growth through CD1d interaction.We now creating a protocol on a clinical trial for T cell lymphoblastic leukemia using NKT cells.