Concanavalin A Inhibition of Tissue Factor (Thromboplastin) Activity

Studies with the jackbean lectin, concanavalin A, were undertaken to clarify the relationship between tissue factor and the cell membrane of cultured fibroblasts. Concanavalin A blocks the coagulant activity of tissue factor of cultured human skin fibroblasts and also rabbit brain. The inhibitory effect, which is dose-dependent and reversed by alpha-methyl-D-mannopyranoside, cannot be explained by an effect on other reactants necessary for clot formation. These results support the contention that tissue factor is located on the cell surface. Since concanavalin A does not affect adhesion-related phenomena in cultured cells, these results also suggest that tissue factor produced by trypsinized fibroblasts is a consequence rather than the cause of cell adhesion and that tissue factor is not synonymous with the adhesive site on the cell surface.