Sequential shifts in the three major glycosphingolipid series are associated with B cell differentiation

Cell surface glycolipid expression as well as total glycolipid content of various B cell lines, representative of different B cell stages, and normal B lymphocytes were examined. Glycolipids, made up of a carbohydrate chain attached to a lipid called ceramide, are classified in four main 'series'. These series are defined according to the identity and chemical bonding of the sugars closest to the ceramide moiety. The pre-B cell lines contained lacto-series type II chain-based glycolipids and II3-alpha-N-acetyl-neuraminosyllactosylceramide (GM3) ganglioside. Upon differentiation, the lacto-series synthesis was shut down whereas compounds of the globo-series appeared: resting lymphocytes and lymphoblastoid cell lines (LCL) expressed GM3, globotriaosylceramide (Gb3), and globoside (Gb4). At a later stage of B cell differentiation, biosynthesis of the ganglio-series was extended and myeloma cells expressed II3-alpha-N-acetyl-neuraminosylgangliotriosylceramide (GM2). At the cell surface, in addition to Gb3, that we previously described as specifically expressed on Burkitt's lymphoma cells and on a subset of germinal centre tonsillar B cells, two glycolipids seemed specific of certain B cell lines: Gb4 was strongly positive on six out of eight LCLs and on the low buoyant density fraction of tonsillar B lymphocytes, whereas GM2 ganglioside was only detected on the two myeloma cell lines. These results, demonstrating the stage-dependent expression of certain glycolipids, suggest that these carbohydrate molecules could play functional roles during B cell differentiation.