ANTIGANGLIOSIDE MONOCLONAL-ANTIBODY AA4 SELECTIVELY INHIBITS IGE-INDUCED SIGNAL-TRANSDUCTION PATHWAYS IN RAT BASOPHILIC LEUKEMIA-CELLS

In rat basophilic leukemia 2H3 (RBL-2H3) cells, mAb AA4 binds to two d erivatives of ganglioside GD(1b) that associate with the Src family ki nase p53/56(lym) and a serine kinase. Pre-incubation of cells with mAb AA4 blocks immunoglobulin E (IgE) mediated histamine release. In the present study we investigated the effect of incubation with mAb AA4 on signal transduction events. In addition to stimulation of the high af finity IgE receptor (FceRI), cells were also activated by the calcium ionophore A23187 and the acetylcholine agonist carbachol in RBL-2H3 ce lls transfected with the G protein-coupled m3 muscarinic receptor. Inc ubation of cells with mAb AA4 in a dose-dependent manner inhibited the following FcsRI-induced signal transduction events: the increase of i ntracellular free calcium, phosphoinositol breakdown, tyrosine phospho rylation of proteins including the beta- of FcERI and secretion. Howev er, there was no inhibition of degranulation or of these biochemical e vents when cells were stimulated with calcium ionophore or activated v ia a G protein-coupled pathway. Our results demonstrate that mAb AA4 s electively blocks FcERI-induced cell activation at a very early step u pstream of receptor tyrosine phosphorylation. As mAb AA4 has previousl y been found to bind to gangliosides associated with FcERI, inhibition of very early biochemical events may be due to interaction of mAb AA4 with the FcERI induced signal transduction cascade at the receptor le vel. (C) 1997 Elsevier Science Ltd.