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 chain of ANA-positive IgG was 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 mutation (n = 4). (B) Spontaneous GC formation in the spleen of 6–10-wk-old DCBlimp-1^ko mice. GC (PNA⁺ B220⁺, asterisks) was analyzed by IHC. Pictures are representative images (bars, 100 µm). On the right, GL-7⁺B220⁺ GC B cells were quantified by flow cytometry as depicted in representative pictures. Each dot represents an individual mouse and horizontal bars indicate means of three independent experiments.