7228
Although a substantial amount is known about the cellular elements that compose the lymphoid and nonlymphoid components of the secondary lymphoid tissues , information concerning the signals that control the development of the tissues and that maintain the organized tissue microenvironment remain undefined.
 ( DNA: cellular elements, 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:
 ( DNA: cellular elements, None) 