Recombinant tumor necrosis factor and immune interferon act singly and in combination to reorganize human vascular endothelial cell monolayers.

Human endothelial cells (HECs) in confluent primary culture reproduce the epithelioid organization of the vascular lining in situ. The addition of greater than or equal to 20 U/ml recombinant tumor necrosis factor (rTNF) or greater than or equal to 16 U/ml recombinant immune interferon (rIFN-gamma) causes HECs 1) to become elongated, 2) to overlap, 3) to rearrange their actin filaments, and 4) to lose their stainable fibronectin matrix. These changes develop over 72-96 hours and are reversible upon withdrawal of the mediator. In serially passaged HECs similar morphologic changes develop. Furthermore, rTNF and rIFN-gamma are each cytostatic for subconfluent passaged cultures. When added in combination, low concentrations of rTNF and rIFN-gamma act synergistically, whereas higher concentrations (eg, 100 U/ml rTNF and 200 U/ml rIFN-gamma) produce unique morphologic changes. Doubly treated primary HECs extend many long, overlapping, spinelike processes and expose the substratum. Doubly treated passaged HECs become extremely elongated and then shed in large numbers. These in vitro changes in endothelial cell morphology and behavior may underlie immunologically mediated vascular responses in vivo.