14675
We previously reported that human umbilical vein EC provide costimulatory signals to PHA-stimulated PBL via CD2:lymphocyte function-associated Ag-3 and an unidentified ligand pair , resulting in a three- to eight-fold enhancement of IL-2 production .
 ( cell type: PBL, None) , ( protein: CD2:lymphocyte function-associated Ag-3, None) , ( cell type: PHA-stimulated PBL, None) , ( cell type: EC, None) , ( protein: IL-2, None) , ( cell type: human umbilical vein EC, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( cell type: PBL, None) , ( protein: CD2:lymphocyte function-associated Ag-3, None) , ( cell type: PHA-stimulated PBL, None) , ( cell type: EC, None) , ( protein: IL-2, None) , ( cell type: human umbilical vein EC, None) 