BDCA2-ADC binds to and is internalized by BDCA2-expressing cells as efficiently as the parental antibody. (A) Human BDCA2-expressing CHOK1 cells or cynomolgus monkey BDCA2-expressing 293T cells were treated with BDCA2-ADC or BIIB059 at different concentrations. Cell-surface binding of the BDCA2-ADC or BIIB059 was measured by FACS. (B) Human BDCA2-expressing CHOK1 cells were stained with BDCA2-ADC or BIIB059 on ice (binding) and incubated at 37°C for 1, 2 and 4 h (internalization). BDCA2 internalization was determined based on the proportion of BDCA2-ADC or BIIB059 that stayed bound to the cell surface. ADC: antibody–drug conjugate; BDCA2: blood dendritic cell antigen 2; FACS: flow cytometry analysis; hIgG1: human immunoglobulin gamma-1; MFI: mean fluorescence intensity