Structure and Function of a Ganglioside found Exclusively on the Surface of Neuroblastoma cells

我们用神经母细胞瘤后藤细胞和黑色素瘤G361细胞的完整细胞免疫小鼠，获得了两种特异性单克隆抗体（mAb）：mAb I-13和mAb AG 23。通过荧光激活细胞分选仪（fluorescence-activated cell sorter，FACS）分析，发现单克隆抗体I-13能很好地识别神经母细胞瘤细胞后藤和IMR-32，但不能识别其他细胞。另一方面，mAb AG 23识别除后藤外的所有测试细胞。结果表明，mAb I-13的抗原是鞘脂，而AG 23的抗原是糖蛋白，CD 44，5-溴-2 ' -脱氧尿苷（BrdU）处理的后藤细胞（其分化为雪旺细胞）在细胞表面表达CD 44。表达的CD 44种类是编码长胞质尾的造血形式（CD 44 H）。通过血清去除分化为神经细胞的后藤细胞不表达CD 44。另一方面，后藤细胞在分化为雪旺氏细胞和神经细胞后，对单抗I-13的反应性稍低，抗原脂质仅存在于膜微区，称为脂筏。在BrdU处理的后藤细胞中的CD 44也将其自身分配成脂筏，尽管在黑素瘤G361细胞的情况下在质膜组分和脂筏组分中均发现了CD 44。我认为，CD 44在BrdU处理的后藤细胞中可能在细胞分化为雪旺细胞中起重要作用。

We immunized mice with intact cells of neuroblastoma GOTO cells and melanoma G361 cells and obtained two interesting monoclonal antibodies(mAbs), mAb I-13 and mAb AG23, which respectively recognized cell surface antigens. I tried to identify the antigens for two mAbs, and I investigated the differentiation of GOTO cells using these mAbs.By fluorescence-activated cell sorter(FACS)analysis of various cells, the mAb I-13 recognized neuroblastoma cells GOTO and IMR-32 very well, but did not recognize other cells tested. On the other hand, the mAb AG23 recognized all cells tested except GOTO.It turned out that the antigen for mAb I-13 was a sphingolipid and that for AG23 was a glycoprotein, CD44.5-Bromo-2' -deoxyuridine(BrdU)-treated GOTo cells, which are differentiated int Schwann cells, expressed CD44 on the cell surface. The CD44 species expressed was the hemopoietic form(CD44H)encoding long cytoplasmic tail. GOTO cells differentiated into neural cells by serum depletion did not express CD44. On the other hand, GOTO cells became a little less responsive with the mAb I-13 after the differentiation into Schwann as well as neural cells.The antigen lipid was found exclusively in membrane microdomain, called lipid rafts. CD44 in BrdU-treated GOTO cells also partitioned itself into lipid rafts, although it was found in both plasma membrane fractions and lipid rafts fractions in the case of melanoma G361 cells. I think that CD44 in BrdU-treated GOTO cells might play an important role in cells differentiated into Schwann cells.