Efficient Ab production by B cell–specific HSP90b1 KO mice in vivo. (A) Baseline Ig level in the sera of 8- to 12-week-old WT and KO mice (n = 12 per group). P > .05 between WT and KO mice with all isotypes. (B) Mice were immunized with HSA plus alum and bled weekly for 3 times. Mice were then rechallenged with HSA and were bled weekly for 4 additional time points. Serum anti-HSA IgG1 was then quantified by ELISA (n = 4-6 mice per group). P > .05 at all time points. Error bars represent SEM. (C) Mice were killed 1 week after secondary immunization with HSA and alum; 5-μm-thick sections of spleens were stained with PNA (red) and HSP90b1 (green), and analyzed by fluorescence microscopy (200× magnification). Representative images were shown.