Tonic BCR signaling in R406-sensitive and -resistant DLBCL cell lines. Single-cell phospho-flow cytometry was used to assess low-level SYK348 and 352 and BLNK phosphorylation in the absence (green) or presence (red) of BCR crosslinking in R406-sensitive (A) and -resistant (B) DLBCL cell lines. Cells stained with an isotype-matched control Ig are shown in black. The x-axis denotes expression (log scale) and the y-axis indicates cell number.