4264
Mature human lymphocytes are unique targets of 1 alpha,25-dihydroxyvitamin D3 ( 1 alpha,25(OH)2D3 ) in that vitamin D receptors ( VDR ) are not constitutively expressed, and specific cellular activation signals are required for both the up-regulation of VDR and establishment of reactivity to the lipophilic ligand .
 ( protein: vitamin D receptors, None) , ( protein: VDR, None) , ( protein: VDR, None) , ( cell type: human lymphocytes, 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: vitamin D receptors, None) , ( protein: VDR, None) , ( protein: VDR, None) , ( cell type: human lymphocytes, None) 