Transfected CHO cells reaggregate by a homophilic mechanism. CHO cells (Ntm, control, and Ntm pretreated with PI-PLC) were dissociated and allowed to reaggregate for 60 min. Photomicrographs of representative aggregates that formed by Ntm-transfected CHO cells (A), control CHO cells (B), and Ntm-transfected CHO cells pretreated with PI-PLC (C) are shown. To examine the kinetics of reaggregation, aliquots were withdrawn at 15 min intervals, and single cells were counted in a hemocytometer (D). Values are the mean ± SEM for four independent experiments. Analysis of the composition of aggregates formed by a mixture of Ntm-transfected and control CHO cells demonstrates that aggregates are composed predominantly of Ntm-transfected cells (E). Control mixture of CHO-Ntm labeled with diI and diO reveals that the composition of aggregates is equally mixed (F).