Roger R, Bréard J, Comisso M, Bohuon C, Pallardy M, Bertoglio J
Laboratoire d'Immunotoxicologie et de Cancérogenèse, INSERM CJF 93-01, Faculté de Pharmacie Paris XI, Châtenay-Malabry, France.
Cell Immunol. 1996 Feb 25;168(1):24-32. doi: 10.1006/cimm.1996.0045.
The mechanisms leading to target cell killing by the human NK-like cell line YT2C2 have been studied. YT2C2 cells express CD28 antigen and kill B7-expressing targets by a CD28-mediated mechanism which is inhibited by anti-CD28 mAb (CD28.2). The lysis of B7-negative targets, which are also killed by YT2C2, is insensitive to CD28.2, but can be inhibited by cyclosporin A (CsA). CsA reduces degranulation in YT2C2 as measured by BLT-esterase release assays. A total suppression of B7-negative cell lysis was observed in the presence of EGTA, which blocks both degranulation and perforin polymerization, confirming that lysis of this type of target depends solely upon granule exocytosis. In contrast, an additional extracellular EGTA-resistant component in B7-positive target killing was evidenced. These results were consistently obtained with a panel of B7-positive and B7-negative targets, including a Jurkat subclone transfected to express B7 and its parental cell line. Ca2+-independent killing was completed during the first hour of the cytotoxicity assay, whereas EGTA-sensitive lysis increased throughout the whole incubation time. These two lytic mechanisms used by YT2C2 were found to induce two different modes of cell death. Extracellular Ca2+-dependent killing caused apoptotic death in both B7-positive and B7-negative targets, whereas the EGTA-resistant cytolytic pathway, observed exclusively with B7-positive targets, led to necrosis. CD28 triggering in YT2C2 induces, therefore, an additional mechanism of cell killing, independent of granule exocytosis, the nature of which remains to be identified.
对人NK样细胞系YT2C2导致靶细胞杀伤的机制进行了研究。YT2C2细胞表达CD28抗原，并通过一种CD28介导的机制杀伤表达B7的靶细胞，该机制可被抗CD28单克隆抗体（CD28.2）抑制。B7阴性靶细胞也可被YT2C2杀伤，但其裂解对CD28.2不敏感，但可被环孢素A（CsA）抑制。通过BLT酯酶释放试验测定，CsA可减少YT2C2中的脱颗粒现象。在存在EGTA的情况下，观察到B7阴性细胞裂解被完全抑制，EGTA可阻断脱颗粒和穿孔素聚合，证实这类靶细胞的裂解仅依赖于颗粒胞吐作用。相比之下，在B7阳性靶细胞杀伤中发现了一种额外的细胞外EGTA抗性成分。使用一组B7阳性和B7阴性靶细胞（包括转染以表达Bx的Jurkat亚克隆及其亲本细胞系）一致获得了这些结果。不依赖Ca2+的杀伤在细胞毒性试验的第一个小时内完成，而EGTA敏感的裂解在整个孵育时间内都增加。发现YT2C2使用的这两种裂解机制可诱导两种不同的细胞死亡模式。细胞外Ca2+依赖性杀伤在B7阳性和B7阴性靶细胞中均导致凋亡性死亡，而仅在B7阳性靶细胞中观察到的EGTA抗性溶细胞途径导致坏死。因此，YT2C2中的CD28触发诱导了一种额外的细胞杀伤机制，该机制独立于颗粒胞吐作用，其性质仍有待确定。
