Distribution of mutational events within the nonproductive (left panel) and productive (right panel) Vλ rearrangements in CD19+ B cells from a patient with systemic lupus erythematosus. The percentages of mutated codon positions are given and the mutational hot spots are indicated. Mutational hot spots were determined as described in Supplementary materials and methods. Codons used only by a few rearrangements were not considered in the diagram. CDR = complementarity-determining region.