The role of leukemia-derived B7-H1 (PD-L1) in tumor–T-cell interactions in humans - Salih, Helmut Rainer; Wintterle, Sabine; Krusch, Matthias; Kroner, Antje; Huang, Yu-Hwa; Chen, Lieping; Wiendl, Heinz (Experimental Hematology, 2006)