THE ANALYSIS OF THE MECHANISM OF ALLOGRAFT REJECTION USING KNOCK OUT MICES

小鼠CD4T细胞在免疫反应和异种皮肤移植排斥反应中的重要作用已有报道。为进一步阐明CD_4和CD_8T细胞在异种皮肤非协调性排斥反应中的作用，本研究采用了CD_4和CD_8基因敲除[C57BL/6铬-碳化硅(B6；H-2b)背景]小鼠。当将人类皮肤移植到CD8基因敲除小鼠或B6小鼠身上时，两种宿主都在移植后12天内拒绝了人类皮肤移植。相比之下，人类皮肤移植物在CD4基因敲除小鼠中的存活时间显著延长[平均存活时间(MST)=19.3标准差(SD)1.6天；中位数19.9天]。CM基因敲除小鼠14天内完全同种异体C3H/He-SIC(H-2k)皮肤移植物发生排斥反应，提示CD4基因敲除小鼠的非CD4T细胞对同种异体移植排斥反应具有免疫活性。在这些受体小鼠的脾中，CD8T细胞似乎在人类皮肤移植后10天被激活。免疫组织化学分析显示，CD4基因敲除小鼠皮肤移植部位有CD8T细胞的浸润。为了进一步研究CD8T细胞在CD4基因敲除小鼠中的作用，我们在第0天进行了人皮肤移植，并在第0、5、14天注射了抗CD8单抗。这些结果表明：1)CD4T细胞在快速排斥异种异种皮肤中起重要作用；2)CD8T细胞也具有排斥异种皮肤的能力。

An essential role of murine CD4+ T cells in immune reactivity and skin graft rejection in discordant xenogeneic combinations have been reported. The present study was conducted in order to further clarify the roles of CD4+ and CD8+ T cells in discordant skin xenograft rejection, by using CD4 and CD8 knockout [C57BL/6 Cr Sic (B6 ; H-2b) background] mice. When human skins were grafted on CD8 knockout mice or B6 mice, both hosts rejected human skin grafts within 12 days after grafting. By contrast, survival of human skin grafts was significantly prolonged in CD4 knockout mice [mean survival times (MST)= 19.3 _} standard deviation(SD)1.6days ; Medianl9days]. Fully allogeneic C3H/He Sic (H-2k) skin grafts were rejected within 14 days in CM knockout mice, suggesting that non-CD4+ T cells in CD4 knockout mice were immunocompetent for allograft rejection. In spleens of these recipient mice, CD8+ T cells seemed to be activated 10 days after human skin grafting. Immunohistological analysis revealed the infiltration of CD8+ T cells at the site of transplanted human skin on CD4 knockout mice. In order to further examine the role of CD8+ T cells in CD4 knockout mice, human skin grafting was performed on day 0 followed by administration of anti-CD8 monoclonal antibody (mAb) on days 0, 5, and 14. The administration of anti-CD8 mAb caused the significant prolongation of human skin graft survival. These results indicate the following two conclusions : 1) CD4+ T cells have an essential role in rejecting discordant human skin xenografts rapidly, 2) however, CD8+ T cells also are capable of rejecting discordant human skin xenografts.