Fox D A, He X, Abe A, Hollander T, Li L L, Kan L, Friedman A W, Shimizu Y, Shayman J A, Kozarsky K
Division of Rheumatology, Multipurpose Arthritis and Musculoskeletal Diseases Center, University of Michigan Medical School, Ann Arbor 48109, USA.
Immunol Invest. 2001 May;30(2):67-85. doi: 10.1081/imm-100104017.
The CD60 antigen is expressed on a majority of T cells in autoimmune lesions, and anti-CD60 can activate T lymphocytes. CD60 has been defined as the GD3 ganglioside, and subsequently as the 9-O-acetylated form of GD3. However, other evidence suggests that anti-CD60 recognizes a glycoprotein or family of glycoproteins expressed by T lymphocytes. The current studies were undertaken to better define the identity of the CD60 antigen on both T cells and non-T cells. Treatment of intact cells with neuraminidases of various specificities confirmed that detection of the CD60 epitope depends on expression of an alpha2, 8-disialic acid carbohydrate linkage, as is found in GD3 and related gangliosides. However, the sialicacid polymer colominic acid inhibited anti-GD2 and anti-GD3, but not anti-CD60 from binding to cell surfaces. Expression of CD60 did not correlate with expression of GD3 on a variety of cell lines and T cell populations. Expression of CD60 and 9-O-acetyl-GD3 was roughly parallel on some non-T cell lines such as melanoma cells, but on T cells expression of CD60 was consistently greater. Antibodies to GD2, GD3 and 9-O-acetyl-GD3 were ineffective at inhibiting binding of anti-CD60 to CD60+ cells. Activation responses of T cells to anti-CD60 were inducible in either the presence or absence of a response to anti-GD3. A novel inhibitor of glucosyl ceramide synthesis, D-threo-1-phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol (D-t-P4) reduced expression of GD3 much more than CD60 on activated T lymphocytes. Following biotinylation of HUT78 T cells, anti-CD60 immunoprecipitated a 70 kDa antigen. Taken together, the present data and previous findings suggest that anti-CD60 can recognize both a modified form of the GD3 ganglioside and a carbohydrate-dependent complex epitope present on one or more glycoproteins. This glycoprotein epitope may be the more abundant and functionally significant CD60 antigen on T lymphocytes, while 9-O-acetyl-GD3 is likely to be the principal structure recognized by anti-CD60 on melanoma cells. These findings emphasize the complexity of understanding the functional roles of carbohydrate epitopes in cell activation.
CD60抗原在自身免疫性病变中的大多数T细胞上表达，抗CD60可激活T淋巴细胞。CD60最初被定义为GD3神经节苷脂，随后又被定义为GD3的9-O-乙酰化形式。然而，其他证据表明抗CD60识别的是T淋巴细胞表达的一种糖蛋白或糖蛋白家族。目前的研究旨在更好地确定T细胞和非T细胞上CD60抗原的特性。用具有不同特异性的神经氨酸酶处理完整细胞证实，CD60表位的检测取决于α2,8-二唾液酸碳水化合物连接的表达，这在GD3和相关神经节苷脂中也有发现。然而，唾液酸聚合物共聚唾液酸抑制抗GD2和抗GD3，但不抑制抗CD60与细胞表面的结合。在多种细胞系和T细胞群体中，CD60的表达与GD3的表达不相关。在一些非T细胞系如黑色素瘤细胞中，CD60和9-O-乙酰-GD3的表达大致平行，但在T细胞上，CD60的表达始终更高。抗GD2、GD3和9-O-乙酰-GD3抗体在抑制抗CD60与CD60+细胞结合方面无效。无论是否存在对抗GD3的反应，T细胞对抗CD60的激活反应都是可诱导的。一种新型的葡糖神经酰胺合成抑制剂，D-苏式-1-苯基-2-棕榈酰氨基-3-吡咯烷基-1-丙醇（D-t-P4）在活化的T淋巴细胞上使GD3的表达比CD60的表达降低得更多。对HUT78 T细胞进行生物素化后，抗CD60免疫沉淀出一种70 kDa的抗原。综上所述，目前的数据和先前的研究结果表明，抗CD60既能识别GD3神经节苷脂的一种修饰形式，也能识别一种或多种糖蛋白上存在的碳水化合物依赖性复合表位。这种糖蛋白表位可能是T淋巴细胞上更丰富且功能上更重要的CD60抗原，而9-O-乙酰-GD3可能是黑色素瘤细胞上抗CD60识别的主要结构。这些发现强调了理解碳水化合物表位在细胞激活中的功能作用的复杂性。
