Activation of HEL cells by plasminogen, Sk, and serum from a Sk-treated patient.

Cells were loaded with FURA-2-AM, and Ca⁺⁺-mobilizing responses measured. Arrows indicate the addition of agonists. (A) Cells were treated with plasminogen (1 μM), Sk (800 U/mL), and serum (10 μL). (B) The serum used was incubated overnight with Sk coupled to Sepharose beads to deplete Sk-binding antibodies. (C) The serum used was incubated overnight with BSA coupled to Sepharose beads as a control.