Nonsense and missense amino acid mutation analysis. Nonsense and missense amino acid mutation analysis. (A) Percentage of IGH sequences that contained at least one premature stop codon, while being in-frame. (B) Average number of V-region somatic mutations among in-frame sequences with a premature stop codon. The P value is from a two-sided Wilcoxon–Mann–Whitney test. (C) Percentage of observed premature stop codons that occurred in the CDR3. (D) Percentage of amino acid mutations in IgA and IgG sequences at day 7 that were considered radical. Similarity between the germline residue and the mutated residue was assessed by IMGT based on three aspects: hydropathy, volume, and chemical characteristics; a mutation was called “radical” if the residue changed class in at least two aspects. Charles F. A. de Bourcy et al. PNAS 2017;114:5:1105-1110 ©2017 by National Academy of Sciences