CD40-associated TRAF3 and cellular NIK levels in matched LMP1⁺vs LMP1⁻clones of mouse BCL lines. (A) The mouse BCL cell line CH12.LX and a subclone stably transfected with IPTG-inducible WT LMP1 were cultured overnight with IPTG as described in “Methods.” CD40 was immunoprecipitated from whole-cell lysates as in Figure 2, and samples subjected to SDS-PAGE were analyzed for CD40-associated TRAF3 by western blot. A representative of 3 similar blots is presented. (B) Relative CD40-associated TRAF3 levels (presented as mean values ± SE from 3 independent experiments as above), with CD40-associated TRAF3 levels in parent CH12.LX cells set at 1. *P < .0001. (C) Effect of LMP1 expression on relative cellular NIK levels. Whole-cell lysates of the indicated cell lines were blotted for NIK and actin as described in “Methods.”