Activation of glu-plasminogen by uPA in the presence of cells. Plasmin generation rates were determined in the presence of 100 nmol/L glu-plasminogen with 15 pmol/L enzyme as HMW uPA (•), scuPA (⧫), and LMW uPA (▵) or no added enzyme (+, dashed line) in the presence of varying concentrations of U937 cells or Nalm6 cells. Values shown are mean ± standard error (SE), n = 2.