Native BJAB cells were incubated with (A) αNP +/− BPCNeuAc-NP, or (B) αCD22/isotype control, under two different sets of conditions. Pre-Bind/Wash: Cells were pre-incubated with αCD22/isotype control, or αNP +/− BPCNeuAc-NP, at 4° C to allow binding to occur. After washing to remove unbound reagents, cells were warmed to 37 °C to enable internalization. Continuous: αCD22/isotype control, or αNP +/− BPCNeuAc-NP were added to cells at 37 °C without pre-incubation, allowing binding and internalization to proceed continuously. At the indicated time points, cells were treated with pH 3.3 buffer (solid line) to measure internalized αNP or pH 7 buffer (shaded and dotted) to measure total αNP and read by flow cytometry. Grey filled histograms represent αNP without BPCNeuAc-NP (A) or isotype control (B). Dotted traces are total antibody binding, and solid traces are internalized antibody.