Increased TRAF3 expression, hyperactivity of the alternative NF-κB pathway, and extended in vitro survival of B cells in the absence of cIAP1 plus cIAP2. (A-B) Cytoplasmic and nuclear extracts from purified lymph node B cells were subjected to Western blot analysis with antisera directed against the indicated proteins. β-Actin was used as a loading control. (C) Purified lymph node B cells from the indicated mouse lines were incubated in unsupplemented culture medium, and the number of live cells present at the indicated time points were assayed by flow cytometry. Control data are from wild-type, cIap1ΔB, and cIap2^−/− mice. Points represent data from individual mice; and lines connect the mean value obtained at each time point. Data are representative of 3 individual experiments.