CD40-mediated activation of intracellular pathways in B cells requires the presence of TRAF2 and cIAP1/cIAP2. B cells were purified from the spleens of mice of the indicated genotypes and stimulated for the indicated times with CD40L. Whole cell lysates were prepared and subjected to Western blot analysis with antisera directed against the indicated proteins. β-Actin was used as a loading control. Note that, in each case, intervening lanes (which were part of a separate study) between the “0 minutes” and “5 minutes” time points were removed using Adobe Photoshop software Version 10.0.1. All samples in each blot are from the same cells stimulated at the same time and run on the same gel. Duplicate experiments in each case generated similar results.