text: As reported previously by others in immortalized TRAF6 KO MEFs (12, 17, 18) or TRAF6 KO monocytes (39), we found that IL-1 signaling could be restored to immortalized TRAF6 KO MEFs by reexpressing the WT TRAF6 but not by the TRAF6[C70A] mutant, whereas only trace IL-1 signaling was restored by the reexpression of TRAF6[L74H] (Fig.