CD23-MEDIATED CELL SIGNALING

Signal transduction through ligation of the CD23 (Ec epsilon RII) mole cule was analysed in human B cells and monocytes. Monoclonal antibodie s directed against the IgE binding site of CD23 were found to trigger phosphoinositide hydrolysis and calcium mobilization in B cells, but n ot in monocytes. These early events were also obtained with an IgE+ an ti-IgE complex, which supposedly mimicks the physiological situation o f a multivalent antigen inducing the cross-linking of cell-bound IgE. Redistribution of CD23 was also found to evoke cAMP accumulation both in B lymphocytes and monocytes. Moreover, we present evidence indicati ng a possible cross-talk between the IL-4- and CD23-induced second mes sengers. We suggest that the alternative transduction pathways elicite d by ligation of CD23 are linked to the CD23 isoform(s) expressed by t hese cells and may result from their association with different sets o f molecules.