Chimeric GA and GG mAbs have similar Fab regions despite differences in Fc. (A) G6, GA, and GG mAbs bind similar to CD137-expressing CHO cells and fail to bind CHO/WT controls. (B) CD137-expressing CHO cells were incubated with different concentrations of purified G6, GA, or GG mAbs. Cells were subsequently stained with G6-APC mAb. Increasing concentrations of purified G6, GA, or GG mAbs blocked binding of G6-APC as indicated by MFI in a dose-dependent fashion. (C) CD137-expressing CHO cells were first incubated with increasing concentrations of G6, GA, or GG and subsequently incubated with human CD137L-muCD8 fusion protein. Cells were then stained with PE-conjugated anti-muCD8. As indicated by MFI, G6, GA, and GG blocked CD137/CD137L interaction in a dose-dependent fashion. Filled histograms represent CHO/WT cells (A) or isotype control mAb (B,C). Open histograms represent staining with the indicated antibody. GA indicates aglycosylated chimeric anti-CD137 mAb; GG, glycosylated chimeric anti-CD137 mAb; G6, mouse antihuman CD137 mAb; and MFI, mean fluorescence intensity.