In vitro stimulation of lymphocytes by vascular endothelial cells. A study with canine arterial and venous endothelial cells.

Data are presented on the ability of arterial and venous endothelial cells to stimulate allogeneic leukocytes. Mixed cultures of allogeneic endothelium and lymphocytes result in proliferation of lymphocytes and generation of cell-mediated cytotoxicity, which do not occur in cultures of syngeneic combinations of endothelium and lymphocytes. Studies of kinetics showed a peak in proliferation at days 6-7. The optimal responder-stimulator ratio appeared to be 15:1. Lymphocytes stimulated with venous endothelial cells were cytotoxic both for arterial and for venous endothelial cells and PHA blasts of the stimulator dog, whereas lymphocytes stimulated with arterial endothelial cells lysed only arterial endothelial cells and PHA blasts of the stimulator. Lysis of syngeneic or third-party allogeneic control targets was virtually absent. Optimal conditions for long-term culture of effector cells from mixed leukocyte endothelial cell cultures were analyzed. Addition of Il 2 every 3 days and the original stimulating antigen every 6 days permitted continuous proliferation of these cytotoxic lymphocytes with preservation of the cytotoxicity pattern.