The T lymphocyte structure CD60 contains a sialylated carbohydrate epitope that is expressed on both gangliosides and glycoproteins.
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.
Fox
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DA
Division of Rheumatology, Multipurpose Arthritis and Musculoskeletal Diseases Center, University of Michigan Medical School, Ann Arbor 48109, USA.
He
X
X
Abe
A
A
Hollander
T
T
Li
L L
LL
Kan
L
L
Friedman
A W
AW
Shimizu
Y
Y
Shayman
J A
JA
Kozarsky
K
K
D015703:Antigens, CD / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D002240:Carbohydrate Sequence; D019040:E-Selectin / Q000378:metabolism; D018985:Epitopes, B-Lymphocyte / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D005732:Gangliosides / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D005963:Glucosylceramides / Q000037:antagonists & inhibitors; D006023:Glycoproteins / Q000737:chemistry / Q000276:immunology*; D006801:Humans; D019169:Jurkat Cells; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D011412:Propanolamines / Q000494:pharmacology; D011759:Pyrrolidines / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology*
C401299:1-phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; C064741:CDw60 antigen; D019040:E-Selectin; D018985:Epitopes, B-Lymphocyte; D005732:Gangliosides; D005963:Glucosylceramides; D006023:Glycoproteins; D011412:Propanolamines; D011759:Pyrrolidines; C026226:ganglioside, GD3; C049132:9-O-acetyl-GD3 ganglioside; D019158:N-Acetylneuraminic Acid