Alterations in ganglioside expression during the differentiation of human mast cells

Gangliosides are physiological components of the outer cell membrane. In th e present study, the role of ganglioside expression during differentiation of human mast cells was evaluated. After 11 days of culture in medium known to induce mast cell differentiation, 70% of peripheral blood mononuclear c ells (PBMC) showed positive staining for the high affinity IgE receptor and tryptase on immunocytochemistry and an associated 20-fold increase of gang lioside GM3 expression. Furthermore, exogenous addition of GM3 during culti vation of PBMC in medium containing low levels of growth factors induced an increase of mast cell specific tryptase. The association of ganglioside ex pression with mast cell. differentiation was confirmed by experiments with the human mast cell line HMC-1. Fc epsilon RI-positive cultured cells enric hed with immunobeads exhibited a 3-fold higher expression of GM3, compared to Fc epsilon RI negative HMC-1 cells. Furthermore, measurable amounts of t he gangliosides GM2, GM1 and GD1a were found only in the Fc epsilon RI posi tive cells. A corresponding transient increase of mRNA for GalNAcT, the key enzyme in the production of these latter gangliosides, could be detected p receding the expression of these gangliosides and the Fc epsilon RI by RT-P CR. Taken together, these data point to a functional role of gangliosides i n the differentiation of human mast cells.