6899
Furthermore, HIV-1 replication is cooperatively stimulated when the distinct LT-betaR and TNF receptor systems are simultaneously engaged by their specific ligands.
 ( protein: LT-betaR, None) , ( protein: TNF receptor systems, 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: LT-betaR, None) , ( protein: TNF receptor systems, None) 