6891
Additionally, virus reactivation in resting PBMCs infected in vitro with HIV-1 was found to be specifically induced by ligands of the CDR2-loop in domain 1 ( D1 ) of CD4 ( virus envelope and anti- CD4 monoclonal antibodies ).
 ( protein: CD4, None) , ( protein: domain 1, None) , ( protein: CDR2-loop, None) , ( protein: virus envelope and anti- CD4 monoclonal antibodies, None) , ( cell type: resting PBMCs, None) , ( protein: CD4, None) , ( cell type: PBMCs, None) , ( protein: D1, 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) , ( protein: domain 1, None) , ( protein: CDR2-loop, None) , ( protein: virus envelope and anti- CD4 monoclonal antibodies, None) , ( cell type: resting PBMCs, None) , ( protein: CD4, None) , ( cell type: PBMCs, None) , ( protein: D1, None) 