MAPK3 and Burkitt lymphoma: To determine if the different BAFFR variants would affect BAFFR surface expression, oligomerization, signaling, and shedding in a comparable and controlled environment, we expressed the variants by lentiviral gene transfer in the Burkitt’s lymphoma line DG-75 (Fig. S2), because this cell line allows the analysis of BAFFR-dependent activation of NF-kB2, AKT, and ERK1/2.