6889
When submitted to an in vitro CD4 cross-linking by iHIV-1 , PBMCs from HIV-1 -infected patients were found to produce virus.
 ( protein: CD4, None) , ( cell type: PBMCs, 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:
 ( protein: CD4, None) , ( cell type: PBMCs, None) 