Fink P J, Rammensee H G, Benedetto J D, Staerz U D, Lefrancois L, Bevan M J
J Immunol. 1984 Oct;133(4):1769-74.
We have shown in the accompanying companion paper that cloned cytotoxic T lymphocytes (CTL) can serve as veto cells in vitro, suppressing primary cytotoxic activity directed against antigens expressed by those cloned CTL but not against third party antigens. We now explore the mechanism of this antigen-specific suppression by cloned CTL, using as a model system the ability of G4, a BALB.B anti-H-2Dd CTL clone, to specifically suppress a primary in vitro anti-H-2b CTL response. G4 cells do not constitutively secrete a suppressor factor, because suppression cannot be mediated by supernatants removed from G4 cells at a time when they are routinely used as veto cells. Furthermore, medium removed from cultures suppressed by G4 will not suppress, indicating that the veto cell function of G4 is not mediated by soluble factors. Full suppression of primary anti-H-2b CTL responses requires that G4 be present throughout the 5-day mixed lymphocyte culture (MLC). Removal of G4 during the first 3 days of MLC results in a drastic reduction in the level of antigen-specific suppression, with a slight but reproducible loss of suppression after veto cell removal on day 4. The addition of G4 during the course of an ongoing MLC reveals that maximal suppression requires the presence of veto cells during the first 24 to 48 hr of culture. Thus, G4 cells must be present both early and late in an MLC to exert maximal veto cell suppression. Several experiments suggest that G4-induced veto cell activity is unlikely to be due to cytolysis of CTL precursors which are capable of recognizing G4. G4 cannot specifically recognize these CTL precursors, and G4 cells are inefficient at lectin-mediated lysis of non-tumor cell targets. Furthermore, we show that G4 cells cannot lyse CTL which recognize them. Finally, dilutions of anti-clonotypic antibodies which completely block both lectin-mediated and specific cytolysis by G4 do not block (and in fact enhance) G4-mediated veto cell activity.
在随附的论文中我们已经表明，克隆的细胞毒性T淋巴细胞（CTL）在体外可作为否决细胞，抑制针对那些克隆CTL所表达抗原的原发性细胞毒性活性，但不抑制针对第三方抗原的活性。我们现在以G4（一种BALB.B抗H-2Dd CTL克隆）特异性抑制原发性体外抗H-2b CTL反应的能力作为模型系统，探索克隆CTL这种抗原特异性抑制的机制。G4细胞不会组成性地分泌抑制因子，因为当它们被常规用作否决细胞时，从G4细胞中去除的上清液无法介导抑制作用。此外，从被G4抑制的培养物中去除的培养基也不会产生抑制作用，这表明G4的否决细胞功能不是由可溶性因子介导的。原发性抗H-2b CTL反应的完全抑制要求G4在为期5天的混合淋巴细胞培养（MLC）全过程中都存在。在MLC的前3天去除G4会导致抗原特异性抑制水平大幅降低，在第4天去除否决细胞后抑制作用会有轻微但可重复的丧失。在正在进行的MLC过程中添加G4表明，最大抑制作用需要在培养的最初24至48小时内存在否决细胞。因此，G4细胞必须在MLC的早期和晚期都存在才能发挥最大的否决细胞抑制作用。几个实验表明，G4诱导的否决细胞活性不太可能是由于能够识别G4的CTL前体细胞的细胞溶解。G4不能特异性识别这些CTL前体细胞，并且G4细胞在凝集素介导的非肿瘤细胞靶标裂解方面效率不高。此外，我们表明G4细胞不能裂解识别它们的CTL。最后，完全阻断G4介导的凝集素介导的和特异性细胞溶解的抗克隆型抗体稀释液不会阻断（实际上会增强）G4介导的否决细胞活性。
