Morelli L, Lemieux S
Centre de Recherche en Immunologie, Institut Armand-Frappier, Université du Québec, Laval, Canada.
J Immunol. 1993 Dec 15;151(12):6783-93.
The NK2.1 alloantigen, one of the few NK-specific markers in the mouse, identifies a subset rather than all splenic NK cells. On the basis of the cell surface expression of a variety of Ag of the lymphocytic and monocytic lineages, we establish that BALB/c NK2.1+ cells are heterogeneous and that their phenotype is quite similar to the one reported for NK1.1+ cells. A NK2.1- cell population of the same size and related phenotype was also identified in fresh NK-enriched cell suspensions. After stimulation with IL-2, the only phenotypic trait that distinguishes NK2.1+ and NK2.1- cell subsets is precisely the expression of the NK2.1 Ag. To investigate whether NK2.1+ and NK2.1- lymphokine-activated killer cells would also be identical in their cytotoxic activity, NK-enriched spleen cells were cultured for 5 days with IL-2, sorted afterward on the basis of NK2.1 expression, and compared for their capacity to lyse YAC-1 targets. NK2.1+ cells are significantly more lytic than NK2.1- cells, suggesting that the anti-NK2.1 mAb, used for cell sorting, could have triggered NK2.1+ cells and enhanced their lytic activity. In support to this hypothesis we show that 1) immobilized anti-NK2.1 mAb induces granule exocytosis by LAK cells, 2) soluble anti-NK2.1 mAb specifically inhibits NK and LAK cell-mediated lysis of 4LO3311 hybridoma cells secreting anti-NK2.1 mAb, and 3) binding of anti-NK2.1 mAb selectively enhances the lysis of NK-sensitive targets. Furthermore, the successful activation of NK2.1+ cells induced by anti-NK2.1 F(ab')2 or F(ab) mAb fragments indicates that the triggering mechanism is different from reverse antibody-dependent cellular cytotoxicity and does not require cross-linking of the NK2.1 molecule. Our results strongly suggest that the NK2.1 molecule is implicated in a post-binding NK cell signaling event, and point out the possible functional relevance of this NK-specific Ag in non-MHC-restricted cytotoxicity.
NK2.1同种异体抗原是小鼠中少数几种NK特异性标志物之一，它识别的是一个亚群而非所有脾NK细胞。基于淋巴细胞和单核细胞谱系多种抗原的细胞表面表达，我们确定BALB/c NK2.1+细胞是异质性的，其表型与报道的NK1.1+细胞的表型非常相似。在新鲜的富含NK细胞的悬浮液中也鉴定出了相同大小且相关表型的NK2.1-细胞群体。用IL-2刺激后，区分NK2.1+和NK2.1-细胞亚群的唯一表型特征正是NK2.1抗原的表达。为了研究NK2.1+和NK2.1-淋巴因子激活的杀伤细胞在细胞毒性活性方面是否也相同，将富含NK细胞的脾细胞用IL-2培养5天，然后根据NK2.1表达进行分选，并比较它们裂解YAC-1靶标的能力。NK2.1+细胞的裂解能力明显强于NK2.1-细胞，这表明用于细胞分选的抗NK2.1单克隆抗体可能触发了NK2.1+细胞并增强了它们的裂解活性。为支持这一假设，我们表明：1）固定化的抗NK2.1单克隆抗体可诱导LAK细胞的颗粒胞吐作用；2）可溶性抗NK2.1单克隆抗体特异性抑制NK和LAK细胞介导的对分泌抗NK2.1单克隆抗体的4LO3311杂交瘤细胞的裂解；3）抗NK2.1单克隆抗体的结合选择性增强对NK敏感靶标的裂解。此外，抗NK2.1 F(ab')2或F(ab)单克隆抗体片段成功激活NK2.1+细胞表明触发机制不同于反向抗体依赖性细胞毒性，且不需要NK2.1分子的交联。我们的结果强烈表明NK2.1分子参与了结合后NK细胞的信号传导事件，并指出了这种NK特异性抗原在非MHC限制的细胞毒性中的可能功能相关性。
