siRNA knockdown of TAPP2 or utrophin inhibits lymphocyte adhesion. (A) BJAB cells were transfected with synthetic siRNAs using a lipid transfection vehicle and harvested after 48 hours. Cell viability was similar under all conditions. TAPP2 expression in the indicated siRNA-treated populations was then assessed by Western blot. (Right panels) Utrophin expression in BJAB cells treated with control or utrophin-specific siRNAs, as determined by utrophin immunoprecipitation and Western blot. (B) Various siRNA-treated populations (indicated by bottom labels) were assessed for adhesion to fibronectin-coated plates in the presence of anti-IgM (1 μg/mL) or PMA (50 ng/mL) stimulation. Results represent the average and SD of triplicate wells from a representative experiment (1 of 5). **P < .05 in a Student t test comparing the indicated specific siRNA-treated groups to the corresponding IgM-stimulated control siRNA group. (C) JVM-3 cells were transfected with control, TAPP2, or utrophin siRNAs using the method described in panel A. Cells were then assayed for adhesion in the presence of anti-IgM (1 μg/mL) or SDF1 (0.5 μg/mL). Results indicate the average and SEM of 2 independent experiments (6 replicate wells). **P < .05 in a Student t test comparing the specific siRNA-treated groups to the correspondingly stimulated control siRNA group. Right panels show Western blot analysis of TAPP2 and utrophin in the siRNA-treated cells. (D) Nalm-6 cells were transduced with lentiviral vectors expressing control or TAPP2-specific shRNAs and then assayed for adhesion in the presence of increasing SDF1 concentrations (0.2, 0.5, 1 μg/mL), indicated by a triangle. Results indicate the average and SEM mean of 2 independent experiments (6 replicate wells). **P < .05 in a Student t test comparing the TAPP2 shRNA-transduced group to the correspondingly stimulated control shRNA group. Right panel shows Western blot analysis of TAPP2 in the cells transduced with shRNA-lentivirus.