Characterization of ANA IgG and GC response. (A) Sequence analysis of ANA IgG from hybridomas. Hybridomas were generated by splenocytes of 4-mo-old DCBlimp-1^ko mice. Total heavy and light chains of ANA-positive IgG were amplified and sequenced. Mutations were determined by comparison with the mouse genomic sequence database. Numbers in each pie graph represent the number of clones categorized by the number of mutations (n = 4). (B) Spontaneous GC formation in the spleen of 6–10-wk-old control and DCBlimp-1^ko mice. On the left, GCs were analyzed by immunohistochemistry using FITC-PNA (green) and PE-conjugated anti-B220 (red). Graph shows quantification of GCs in the spleens of mice. Representative IHC images are shown (bars, 260 μm). On the right, GL-7⁺B220⁺ GC B cells were quantified by flow cytometry as depicted in representative dot plots. Each dot represents an individual mouse and horizontal bars indicate means of three independent experiments.