Tyrosine phosphorylation of p72syk induced by anti-9-O-acetyl GD3 antibodies in human peripheral blood mononuclear cells.

We have previously shown that a subpopulation of peripheral blood CD4+ T-cells are strongly positive for the ganglioside 9-O-acetyl GD3. Treatment of peripheral blood mononuclear cells (PBMC) with monoclonal anti-9-O-acetyl GD3 antibodies (MoAb 27A) induced a dose-dependent proliferative response in the cells. Here we show that binding of 27A IgG to PBMC induces rapid tyrosine phosphorylation of p72syk and mobilization of phosphoinositides. Equal phosphorylation was not seen after stimulation of PBMC with anti-GD3 antibodies (MoAb R24) despite the apparent similar cell surface distribution of the two gangliosides. This suggests that the O-acetyl modification enhances the signal transduction mediated by GD3 ganglioside.