Fig A1.

Binding specificity of anti–programmed death-1 (PD-1) monoclonal antibody (MDX-1106). (A) MDX-1106 (20 μg/mL) was tested for binding to various T cell immunogloblulin (Ig) family members by standard enzyme-linked immunosorbent assay using plate-coated Fc-fusion proteins (R&D Systems, Minneapolis, MN). Goat antihuman immunoglobulin G (IgG; kappa chain specific) polyclonal antibody conjugated with horseradish peroxidase (Jackson ImmunoResearch, West Grove, PA) was used as secondary antibody (Ab). (B) MDX-1106 inhibits binding of both B7-H1 and B7-DC to PD-1. Transfected Chinese hamster ovary cells expressing PD-1 molecules were incubated with serial dilutions of MDX-1106 or an isotype-matched control antibody, followed by addition of fluorescein isothyocyanate–conjugated recombinant human B7-H1-Fc or B7-DC-Fc fusion proteins and flow cytometric analysis.