2 es cells cultured for 5 passages in the presence of lif in contrast panel c of fig2 shows ssea 1 expression determined by fluorescent flow cytometry in mesc20 clone 2 es cells cultured for 5 passages in the absence of lif comparison of panels b and c illustrates that expression of the primitive cell marker ssea 1 was not decreased following removal of lif from clone 2 es cells indicating that inhibition of e cadherin activity represents a technique by which differentiation of cells in monolayer culture may be retarded and cell numbers increased even without the addition of lif panel d of fig2 shows a phase contrast microscopy image illustrating the formation of three dimensional embryoid bodies following culture of clone 2 es cells in suspension culture in the absence of lif the results show that although partial inhibition of e cadherin activity is sufficient to retard differentiation of murine cells when grown in monolayer culture without lif it is not sufficient to retard differentiation of murine cells in suspension culture without lif accordingly it will be appreciated that in the event that it is wished to retard the differentiation of murine cells in suspension culture it will be preferred that e cadherin should be substantially totally inhibited in the event that it is wished to retard the differentiation of murine cells in monolayer culture this may be achieved using partial or total inhibition of e cadherin activity by the same token it will be recognised that an inhibitor of e cadherin activity that is only capable of partial inhibition of e cadherin may still be used to.