Bonavida B, Katz J
J Immunol. 1985 Sep;135(3):1616-23.
The present study examines the role of nonclass I MHC target membrane structures involved in lysis by cytotoxic lymphocytes in the lectin-dependent cellular cytotoxicity (LDCC) system. Cytotoxic cells of rodents and humans have been shown to nonspecifically lyse target cells of different origins and species. The mechanism by which such cytotoxicity takes place is not known, although several hypotheses have been put forth. This study examines the role of class I MHC expression on target cells and Lyt-2 antigens on the cytotoxic cells in both allogeneic and xenogeneic LDCC systems. Human peripheral blood lymphocytes, and murine-allosensitized cytotoxic T lymphocytes (CTL) are used as effector cells, and class I MHC-negative Daudi and class I MHC-positive Raji human target cells are used. The studies reveal that in LDCC, human lymphocytes lyse HLA-negative Daudi targets to the same extent as HLA-positive Raji targets. This was shown by the 51Cr-release assay as well as the single cell assay. Furthermore, allosensitized murine CTL lyse Daudi and Raji in LDCC, demonstrating that lysis of class I negative targets is achieved by xenogeneic CTL. Target cells treated with papain were found to be resistant to lysis in LDCC. However, incubation of papain-treated targets for 1 to 2 hr resulted in recovery of cytotoxicity. In the single cell assay, the papain treatment of targets slightly reduces the frequency of binders but significantly reduces the frequency of killers, revealing that the papain-sensitive structures are essential during the lethal hit stage of lysis. Monoclonal anti-Lyt-2 antibody inhibits lysis of both Daudi and Raji targets by murine CTL. The lack of discrimination between mouse and human targets by murine CTL suggests that the Lyt-2 molecule may have a different role than merely interacting with the target cell. In the LDCC system, we propose that class I MHC molecules are not essential for lysis. Several papain-sensitive and -insensitive target cell structures may participate in the cytolytic mechanism, and we propose that both the lectin and Lyt-2 molecules are involved in the perturbation of cell membrane conformation essential for lysis.
本研究探讨了在凝集素依赖性细胞毒性（LDCC）系统中，参与细胞毒性淋巴细胞裂解作用的非I类主要组织相容性复合体（MHC）靶膜结构的作用。啮齿动物和人类的细胞毒性细胞已被证明能非特异性地裂解不同来源和物种的靶细胞。尽管已经提出了几种假说，但这种细胞毒性发生的机制尚不清楚。本研究考察了I类MHC在靶细胞上的表达以及细胞毒性细胞上的Lyt-2抗原在同种异体和异种LDCC系统中的作用。使用人外周血淋巴细胞和小鼠同种异体致敏的细胞毒性T淋巴细胞（CTL）作为效应细胞，并使用I类MHC阴性的Daudi细胞和I类MHC阳性的Raji人靶细胞。研究表明，在LDCC中，人淋巴细胞裂解HLA阴性的Daudi靶细胞的程度与HLA阳性的Raji靶细胞相同。这通过51Cr释放试验以及单细胞试验得以证明。此外，同种异体致敏的小鼠CTL在LDCC中裂解Daudi细胞和Raji细胞，表明异种CTL可实现对I类阴性靶细胞的裂解。发现用木瓜蛋白酶处理的靶细胞在LDCC中对裂解具有抗性。然而，将用木瓜蛋白酶处理的靶细胞孵育1至2小时后，细胞毒性得以恢复。在单细胞试验中，木瓜蛋白酶处理靶细胞会略微降低结合细胞的频率，但显著降低杀伤细胞的频率，这表明木瓜蛋白酶敏感结构在裂解的致死性打击阶段至关重要。单克隆抗Lyt-2抗体可抑制小鼠CTL对Daudi和Raji靶细胞的裂解。小鼠CTL对小鼠和人靶细胞缺乏区分能力，这表明Lyt-2分子可能具有不同于仅仅与靶细胞相互作用的作用。在LDCC系统中，我们提出I类MHC分子对于裂解并非必不可少。几种木瓜蛋白酶敏感和不敏感的靶细胞结构可能参与了细胞溶解机制，并且我们提出凝集素和Lyt-2分子均参与了对裂解至关重要的细胞膜构象的扰动。
