Interactions between lymphoid tumor cells and isolated liver endothelial cells.

Interactions were studied between highly metastatic murine MB6A lymphosarcoma cells and rat liver endothelial cells that had been isolated by collagenase perfusion and purified by unit gravity sedimentation. Experiments were performed on the day of isolation. MB6A cells were observed to adhere to the endothelial cells. Addition of rat serum had a striking effect: The endothelial cells spread over the MB6A cell surface, engulfing the tumor cells. The factor involved was nondialyzable and also was present in rat plasma. Similar interactions were seen with highly metastatic ESb and MDAY-D2 lymphoma cells and with nonmetastatic Eb cells. Low-metastatic GRSL 34 leukemia and TA3/Ha ascites mammary carcinoma cells did not adhere to the endothelial cells. With this in vitro model the molecular mechanisms of adhesion to liver endothelium were studied. As a first step, univalent antibodies against MB6A cells were found to inhibit adhesion, indicating involvement of specific cell surface molecules.