Ablation of Noxa results in memory B-cell responses of reduced quality and quantity. Mice were immunized with TNP-KLH and boosted after 28 days. Seven days after boost, antibody responses were analyzed. (n = 5 per genotype; 1 of 2 experiments with similar results is shown). (A) TNP-specific antibody responses were assessed by ELISA under limiting serum dilutions with fixed TNP-BSA coating (5 ug/mL). Shown are IgM (top), IgG1 (middle), and IgG2b (bottom) responses (WT indicates wild-type; and p.i.-serum, pre-immune serum, sera isolated from mice before immunization). (B) TNP-specific IgG1 antibody responses were assessed by ELISA under limiting TNP-BSA coating, using high (15:1, top panel) and low (4:1, bottom panel) avidity antigen. Results are expressed as percentage of the response at maximum antigen levels. (C) Numbers of TNP-specific IgG1 producing plasma cells in the spleen, measured by ELISPOT. Mean and SEM are shown (*P < .05, **P < .005, and ***P < .0001; Student t test).