13839
Porcine MHC class II antigens are potent stimulators of direct T-cell recognition by human CD4+ T cells and are, therefore, likely to play an important role in the rejection responses to transgenic pig donors in clinical xenotransplantation .
 ( cell type: human CD4+ T cells, None) , ( protein: Porcine MHC class II antigens, 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:
 ( cell type: human CD4+ T cells, None) , ( protein: Porcine MHC class II antigens, None) 