p50/105 and p52/p100 are required for LTβR-induced NF-κB activities. (A) LTβR-induced NF-κB activation is completely abolished in p50 and p52 double mutants and perturbed in p50 and p52 single-mutant MEFs. MEFs of the indicated genotype were stimulated with agonistic anti-LTβR antibody for the indicated times and subject to a NF-κB EMSA. Three specific activities are indicated by arrows as in Figure 1A. (B) Identification of p50- and p52-containing NF-κB activities. Extracts from wild-type, Nfkb1^-/-, and Nfkb2^-/- MEFs, untreated or stimulated for 24 hours with agonistic LTβR antibody, were subject to supershift analyses with the indicated NF-κB antibodies and competitor oligonucleotides.