Glycosylation of human leukocyte locus A molecules is dependent on the cell type

Peripheral blood monocytes and B cells were isolated from a normal donor, and a portion of the B cells was transformed by the Epstein‐Barr virus (EBV). Human leukocyte locus A (HLA) class‐I and class‐II molecules were immunoprecipitated by specific monoclonal antibodies after cell labeling with [ 3 H]mannose. Glycopeptides of HLA molecules were obtained by pronase digestion and were analysed by lectin‐affinity chromatography. Complex structures were hydrazinolysed, and their sialic acid content was analysed by ion‐exchange chromatography, whereas the high‐mannose structures were separated by HPLC. In normal cells, class‐I antigens bear principally fucosylated biantennary structures while HLA‐DR class‐II antigens bear bi‐, tri‐ and tetraantennary structures and high‐mannose structures. HLA antigens are more sialylated on normal B cells than on normal monocytes. An EBV cell line had a very different pattern of HLA‐antigen glycosylation when compared with the original B cells. In the transformed cells, the fractions containing biantennary structures are largely decreased. In contrast, an increase of the tri‐ and tetra‐antennary structure fractions is noticed, particulary in class‐II molecules, while both triantennary and high‐mannose structures are increased in class‐I molecules. Moreover, when compared to normal B cells, the complex structures of class‐I antigens in the EBV‐transformed B‐cell line are undersialylated while they are oversialylated in the case of the class‐II molecules.