Tanaka K, Hancock W W, Osawa H, Stunkel K G, Alberghini T V, Diamantstein T, Tilney N L, Kupiec-Weglinski J W
Harvard Medical School, Department of Surgery, Brigham and Women's Hospital, Boston, MA 02115.
J Immunol. 1989 Nov 1;143(9):2873-9.
ART-18, a mouse IgG1 mAb recognizing the IL-2 binding domain of the rat p55 subunit IL-2R molecule, prevents graft rejection in various experimental models, although its mechanism of action in vivo, like that of anti-IL-2R mAb generally, remains elusive. These studies were designed to define whether IL-2R+ T effector cells were actually eliminated or their function merely inhibited by comparing directly the in vitro and in vivo efficacy of intact ART-18 and its F(ab)/F(ab')2 fragments. Addition of each mAb preparation profoundly suppressed MLR set up between naive LEW responders and x-radiated BN stimulators, suggesting that mAb fragments retained Ag binding functions in vitro. However, both ART-18 F(ab) and F(ab')2 were ineffectual in vivo as judged by their inability to affect acute (8 days) rejection of (LEW X BN)F1 cardiac allografts in LEW recipients (graft survival ca. 11 and 9 days, respectively, compared to ca. 21 days after therapy with intact ART-18, p less than 0.001). The sera levels of ART-18 and ART-18 F(ab')2 were 4 to 5 micrograms/ml, but only less than 0.5 micrograms/ml of F(ab) could be detected. The therapeutic failure of ART-18 fragments was unrelated to potential host sensitization, as rat antimouse F(ab) or F(ab')2 serum IgG titers remained in the same range as those against intact ART-18. The role of the Fc portion of Ig in the mode of action of ART-18 was then tested further by flow microfluorimetry analysis of host mononuclear spleen cells and immunoperoxidase stains of the graft infiltrate. IL-2R+ cells were abundant in rats treated with ART-18 fragments, comparable to acutely rejecting controls. In contrast, IL-2R expression was abolished in animals undergoing ART-18 therapy. The elimination of IL-2R+ cells is required to prolong cardiac allograft survival in rats after IL-2R targeted treatment with ART-18 mAb.
ART-18是一种识别大鼠p55亚基IL-2R分子的IL-2结合域的小鼠IgG1单克隆抗体，在各种实验模型中可预防移植排斥反应，尽管其体内作用机制与一般抗IL-2R单克隆抗体一样仍不清楚。这些研究旨在通过直接比较完整的ART-18及其F(ab)/F(ab')2片段的体外和体内疗效，来确定IL-2R+ T效应细胞是被实际清除还是其功能仅仅被抑制。添加每种单克隆抗体制剂都能显著抑制由未致敏的LEW应答者和经X射线照射的BN刺激者建立的混合淋巴细胞反应，这表明单克隆抗体片段在体外保留了抗原结合功能。然而，通过它们无法影响LEW受体中(LEW×BN)F1心脏异体移植物的急性（8天）排斥反应来判断，ART-18 F(ab)和F(ab')2在体内均无效（移植物存活时间分别约为11天和9天，而用完整的ART-18治疗后约为21天，p<0.001）。ART-18和ART-18 F(ab')2的血清水平为4至5微克/毫升，但只能检测到低于0.5微克/毫升的F(ab)。ART-18片段的治疗失败与潜在的宿主致敏无关，因为大鼠抗小鼠F(ab)或F(ab')2血清IgG滴度与抗完整ART-18的滴度保持在相同范围内。然后通过宿主单核脾细胞的流式微荧光分析和移植物浸润的免疫过氧化物酶染色进一步测试了Ig的Fc部分在ART-18作用模式中的作用。在用ART-18片段治疗的大鼠中，IL-2R+细胞丰富，与急性排斥对照组相当。相比之下，接受ART-18治疗的动物中IL-2R表达被消除。在用ART-18单克隆抗体进行IL-靶点治疗后，消除IL-2R+细胞是延长大鼠心脏异体移植物存活时间所必需的。
