Isolated naïve B cells were centrifuged in antibiotic-free, serumcontaining media as recommended by the Amaxa P3 Primary Cell 4D-Nucloefector X Kit L [Lonza, Cologne, Germany, V4XP-3024] at 300 × g for 10min at room temperature. Cells were resuspended in room temperature Amaxa buffer as suggested by the manufacturer for primary cells. 2–3 × 10^6 cells/100 µL cuvette was the final concentration of cells used for nucleofection.B cells were nucleofected with either mock (no siRNA), 1.5µM of ON-TARGETplus Non-targeting Control Pool [Dharmacon, Lafayette, CO, D-001810-10-05] or SMARTpool ON-TARGETplus human IRF4 siRNA [Dharmacon, LU-019668-00-0005]. 1–1.5µM ON-TARGETplus Targeted Control GAPD Pool [Dharmacon, D-001830-10-05], 1–1.5µM of ON-TARGETplus AICDA siRNA [Dharmacon, LU-021409-00-0005], and 1.5µM siGLO green transfection indicator siRNA [Dharmacon, D- 001630-01-05] were also used. Cells were nucleofected using program EO-117 for primary human B cells of the Amaxa 4D Nucleofector system [Lonza] composed of the core unit and the X unit.