Comparison of the fine specificities of anti-VpreB MoAbs by FACS and BIAcore analysis. (Top) Surface FACS analysis of VpreB and μ chains on human proB-cell (JEA2), preB-cell (NALM6), and B-cell (NAMALWA) lines, using the 4G7 anti-VpreB, SLC1, SLC2,10,21and anti-μ MoAbs. The 4G7 MoAb is PE-labeled and unconjugated SLC1 and SLC2 are shown by a PE-conjugated goat antimouse IgG+IgM (H+L). Wherever indicated (line 2), JEA2 cells were cultured with 20 ng/mL of IL-7 for 4 days. (Bottom) Binding of anti-VpreB MoAbs to immobilized VpreB-containing recombinant proteins using the BIAcore apparatus. In two separate experiments, 20 μL (20 μg/mL) of 4G7, SLC1, and SLC2 was injected at a flow rate of 5 μL/min in HBS buffer on four surfaces containing 700, 410, 1,400, and 900 RU of VpreB, scΨL, Fab-like NALM6, and Fab-like 1E8, respectively. The resulting sensorgrams are superimposed.