B7-H1 expression in MM plasma cell lines and in MM and MGUS plasma cells. (A) B7-H1 expression measured by flow cytometry in CD138-selected cells from MM, MGUS, and healthy donors (HDs). (B) Same as (A) but after 24-hour incubation with 500 IU/mL IFN-γ. Two representative histograms of B7-H1 expression of MM cells are also shown. (C) B7-family molecule expression in RPMI 8226 and U266 cells, with or without incubation of 500 IU/mL IFN-γ for 24 hours before flow cytometric analysis. One representative histogram of B7-H1 expression in RPMI 8226 cells is also shown.