Requirement of immobilization of CD137 ligand agonists.

<p>SGH-MM5 (A and B) or SGH-MM6 (C and D) cells at a density of 10⁶ cells/ml were cultured on uncoated plates (PBS), or on plate-bound Fc, CD137-Fc, mouse IgG (MOPC21) or anti-CD137 ligand antibody (clones 5F4 and C65-485) or on uncoated plates (PBS), or to which Fc or CD137-Fc proteins were added soluble at 10 µg/ml. (A) Percentage of dead cells (left panel) and number of total live cells (right panel) were determined after 24 h via trypan blue staining. (B) Extent of apoptosis of cells in (A) was determined by Annexin V and 7-AAD staining. (C) Percentages of dead cells were determined at indicated times via trypan blue staining. (D) IL-8 concentrations in 24 h cell supernatants as determined by ELISA. Depicted are means ± standard deviations of triplicate measurements. * p<0.05.