T-cell inhibition by MM plasma cells. (A) CD8⁺ T-cell expansion after a 2-week coculture with irradiated RPMI 8226 MM cells pre-incubated with 500 IU/mL IFN-γ and 20 μM UO126 or anti-B7-H1 or isotype control. (B) CTL activity of CD8-sorted T cells expanded for 2 weeks with irradiated RPMI 8226 cells, against HEK 293, K562, and RPMI 8226 cells. (C) CTL activity against RPMI 8226 cells of CD8-sorted T cells expanded for 2 weeks with irradiated RPMI 8226 cells pre-incubated with 500 IU/mL IFN-γ ^{+ /−} 20 μM UO126 or anti-B7-H1 or isotype control. (D) Same as (C) but with CD8-sorted T cells expanded with irradiated RPMI 8226/DN-hMyD88 cells. (E) Same as (C) but 500 ng/mL LPS instead used for preincubation of stimulator cells in coculture. (F) CTL activity against CD-138 selected MM cells of CD8-sorted T cells expanded for 2 weeks with irradiated CD138-selected samples pre-incubated for 24 hours with 500 IU/mL IFN-γ or 500 ng/mL LPS used as stimulator cells in coculture. Results are means and SD of 4 samples. (G) Same as (B) but against target cells pre-incubated for 1 hour with TLR ligands (500 ng/mL LPS, 2.5 μg/mL PGN, 5 μM ODN) or 500 IU/mL IFN-γ before CTL assay. Data represent mean and SD of experiments performed twice in quadruplicate.