Fig 1: B cell aptamer interaction with CD22 protein(A) B-ALL aptamer (B-ALL1–B-ALL5 and B-ALL31) and control aptamer (Cont.) specificity for CD22 was evaluated using an aptamer qRT-PCR internalization assay with CHO cells expressing CD22 (CHO 22+) and wild-type CHO cells not expressing CD22 (CHO WT). Data are plotted as mean ± SEM; n = 3 biological replicates; mixed effect analysis p > 0.005 with post hoc Bonferroni’s multiple-comparisons test; ∗∗∗p < 0.0001. (B) Dose dependence of B cell aptamer B-ALL1 and Cont. aptamer for CD22. Data are plotted as mean ± SEM; n = 3 biological replicates; 2-way ANOVA, p < 0.0001 with Sidak’s multiple-comparisons post hoc test; ∗p < 0.05, ∗∗p < 0.001, ∗∗∗p < 0.0001. (C) Knockdown of CD22 expression by treatment with anti-CD22 siRNAs. CD22 was detected by anti-human CD22 (green), the cytoplasm was stained with AF568-phalloidin (red), and the nucleus was visualized by TOPRO-3 (blue). Scale bar, 20 μm. (D) qRT-PCR aptamer internalization assay of aptamers B-ALL1, B-ALL2, and Cont. aptamer with CHO 22+ cells and CHO 22+ (siRNA-treated) cells. Data are plotted as mean ± SEM; n = 3 biological replicates; 2-way ANOVA, p < 0.0001 with Bonferroni’s multiple-comparisons post hoc test; ∗∗∗p < 0.0001. (E) B-ALL1 aptamer and Cont. aptamer specificity for recombinant histidine-tagged CD22 or control histidine-tagged protein (glyoxalase) in the presence of epratuzumab or a control IgG1 (bevacizumab). Data are plotted as mean ± SEM; n = 4 biological replicates; one-way ANOVA with multiple-comparisons post hoc test; ∗∗p < 0.001, ∗p < 0.05.