Analysis of chimera of B7-H1 and B7-DC in molecular shield. (A) Schematic of the full-length B7-H1 (B7-H1), full-length B7-DC (B7-DC), and the chimera of B7-H1 and B7-DC (B7-DC/H1) genes. IgV indicates IgV domain; IgC, IgC domain; TM, transmembrane domain; CY, cytoplasmic domain. (B) The expression of B7-DC/B7-H1 chimeric genes on P815 cells. The expression of B7-DC on B7-DC/P815 (top left) or B7-DC/H1/P815 (top right) were determined by flow cytometry analysis using anti–mouse B7-DC mAb (clone TY25). The ability of B7-DC/P815 (bottom left) or B7-DC/H1/P815 (bottom right) to bind PD-1Ig fusion protein was also determined similarly. (C) Extracellular domain swap between B7-H1 and B7-DC does not affect molecular shield. Activated 2C CTLs were incubated at indicated E/T ratios with ⁵¹Cr-labeled mock/P815, full-length B7-DC/P815, or B7-DC/H1/P815 cells in the presence of control IgG or anti–mouse B7-DC mAb for 4 hours. CTL activity was determined in a ⁵¹Cr release assay. Each point is the mean of triplicates with SD. The data are representative of at least 3 experiments.