Ono K, Takahashi K, Hirabayashi Y, Itoh T, Hiraga Y, Taniguchi M
Department of Immunology, School of Medicine, Chiba University, Japan.
Cancer Res. 1988 May 15;48(10):2730-3.
A mouse melanoma (B16) antigen was investigated at a cellular level by three blocking experiments using monoclonal antimelanoma antibodies, soluble melanoma antigen, and enzyme-treated B16 melanoma cells as inhibitors. The activity of antimelanoma cytotoxic T-lymphocytes (CTL) was specifically reduced by addition of the mixture of two monoclonal antimelanoma antibodies, one (M2590) recognizing the cross-species melanoma epitope on GM3(NeuAc) and the other (M562) reactive with the mouse melanoma-specific epitope on protein molecules. The CTL activity was also blocked by GM3 liposome as well as by the soluble antigen. However, 3,000 times more GM3 than the soluble melanoma antigen is required to obtain a similar inhibitory effect. When pronase-treated B16 melanoma cells, which have had protein molecules removed but GM3 left intact on the surface, were used as an inhibitor, their blocking activity was greatly reduced but was still partly observed at a high inhibitor/target ratio. These results indicate that the melanoma antigen is not GM3 itself but is composed of the GM3-protein complex. This finding was also supported by using an interleukin 2-dependent CTL clone whose activity was blocked by both M562 and M2590. Antimelanoma CTL were found to belong to a double-negative T-cell population with Thy-1+, Lyt-2-, L3T4- phenotypes. L3T4+ T-cells were also demonstrated to be necessary for induction of double negative antimelanoma CTL.
通过三项阻断实验在细胞水平上研究了小鼠黑色素瘤（B16）抗原，实验使用单克隆抗黑色素瘤抗体、可溶性黑色素瘤抗原以及经酶处理的B16黑色素瘤细胞作为抑制剂。添加两种单克隆抗黑色素瘤抗体的混合物可特异性降低抗黑色素瘤细胞毒性T淋巴细胞（CTL）的活性，其中一种抗体（M2590）识别GM3（NeuAc）上的跨物种黑色素瘤表位，另一种抗体（M562）与蛋白质分子上的小鼠黑色素瘤特异性表位反应。GM3脂质体以及可溶性抗原也可阻断CTL活性。然而，要获得类似的抑制效果，所需的GM3比可溶性黑色素瘤抗原多3000倍。当使用经链霉蛋白酶处理的B16黑色素瘤细胞作为抑制剂时，其表面的蛋白质分子已被去除，但GM3保持完整，此时其阻断活性大大降低，但在高抑制剂/靶细胞比例下仍可部分观察到。这些结果表明，黑色素瘤抗原不是GM3本身，而是由GM3 - 蛋白质复合物组成。使用白细胞介素2依赖性CTL克隆也支持了这一发现，其活性被M562和M2590均阻断。发现抗黑色素瘤CTL属于具有Thy - 1 +、Lyt - 2 -、L3T4 - 表型的双阴性T细胞群体。还证明L3T4 + T细胞对于诱导双阴性抗黑色素瘤CTL是必需的。
