Changes in glycan branching and sialylation of the Thy-1 antigen during normal differentiation of mouse T-lymphocytes.

The glycans of the Thy-1 antigen present on thymocytes and lymph-node T-lymphocytes were investigated after external labelling of the cells. Neuraminidase, endoglycosidase H and endoglycosidase F were used in combination with sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and isoelectric focusing in order to characterize the nature of the glycans on 125I-labelled and immunoprecipitated Thy-1. Glycopeptides were prepared from Thy-1 obtained from cells labelled by periodate/boro[3H]hydride treatment. The glycopeptides were separated by affinity chromatography on concanavalin A-Sepharose and analysed by gel filtration. The results show that both types of cells possess Thy-1 molecules with three N-linked carbohydrate chains, of which one is of 'high-mannose' type and the other two of triantennary and biantennary 'complex' type. The ratio of triantennary/biantennary chains was decreased on Thy-1 of mature cells compared with that of immature cells, but instead more sialic acid was present on these chains. Deglycosylated Thy-1 appeared to be of the same size regardless of origin, indicating that only the carbohydrate moiety differs between Thy-1 molecules of the two cell types.