DEVELOPMENT OF MATERIALS WHICH HAVE INHIBITORY ACTIVITY ON GRAFT-VERSUS-HOST DISEASE ACCOPANIED BY BONE MARROW TRANSPLANTATION

本研究旨在开发一种特异性的方法来抑制器官移植和输血中可能发生的移植物抗宿主病。为此，我们使用了一种单抗(RE2抗体)，它能特异性地诱导活化的淋巴细胞死亡，但不能诱导静止的淋巴细胞和体细胞死亡。该单抗的特点是：1)RE2直接杀死依赖IL-2的T细胞克隆、ConA或LPS激活的脾细胞和淋巴结细胞，而不是胸腺细胞，不需要血清补体的参与。RE2的Fab片段不具有细胞杀伤活性，而Fab片段的交联会重建其细胞毒性。2)扫描电子显微镜观察到，RE2作用后5min内，细胞膜上形成了巨大的孔洞。在细胞溶解过程中没有DNA断裂和线粒体肿胀的迹象，表明细胞死亡既不是凋亡，也不是典型的坏死。3)表达克隆研究表明，RE2与包括H-2K、K在内的一系列MHC-I类分子发生反应，为膜刺激活化淋巴细胞死亡的新途径提供了证据。推测RE2通过与MHC-I类分子相关的未知分子诱导细胞死亡。

The present study was carried out to develop a specific method to inhibit the graft versus host disease which may occur in organ transplantation and blood transfucion. For this purpose, we used a monoclonal antibody (RE2 antibody) which induces cell death specifically in activated lymphocytes but not resting lymphocytes nor somatic cells.The features of the RE2 mAb are following : 1) RE2 directly killed IL2-dependent T cell clones, ConA- or LPS-activated spleen cells and lymph node cells, but not thymocyte, without participation of serum complement. Fab fragments of RE2 had no cytolytic activity, while the cross-linking of Fab fragments reconstituted the cytotoxicity. 2) Giant holes on the cell membrane were formed within 5 minutes after the treatment with RE2, as observed by scanning electron microscopy. There was no indication of DNA fragmentation nor swelling of mitochondria during the cytolysis, suggesting that the cell death is neither apoptosis nor typical necrosis. 3) Expression cloning study revealed that RE2 reacts with a family of MHC class I molecules including H-2K^K.These results provide evidence for a novel pathway of cell death of activated lymphocytes by membrane excitation. It was also speculated that RE2 induces cell death through unknown molecule which associated with MHC class I molecules.