## Increased HCDR3 length does not correlate with affinity maturation events.

(A) Peripheral blood antibody sequences were grouped by mutation frequency and the percent of sequences in each group that contained codon-length (non-frameshift) insertions was calculated for each donor. All values for healthy donors from Group 1 (n = 4) and Group 2 (n = 3) are shown in the left panel, with the mean percentage ± SEM shown for each mutation value. In the right panel, sequences from Group 1 healthy donors were segregated by B cell subset, and the best-fit linear regression for each subset is shown. (B) Peripheral blood antibody sequences were grouped by HCDR3 length (in amino acids) and the mean number of mutations for each HCDR3 length group was calculated for each donor. As in Figure 1A, the left panel shows the mean ± SEM for all donors in Group 1 and Group 2. The right panel shows the best-fit linear regression of each B cell subset for Group 1 donors. The percent of sequences within each HCDR3 length group containing non-frameshift insertions also was calculated. In the left panel, the mean percentage ± SEM for all donors in Group 1 and Group 2 is shown. In the right panel, the best-fit linear regression of each B cell subset is shown for Group 1 donors. (C) Peripheral blood antibody sequences from Group 1 healthy donors were grouped by donor into naïve and memory subsets and the percent of sequences containing long HCDR3s (≥24 amino acids in length, or two standard deviations above the mean HCDR3 length). The percentages for each donor are shown, with the mean ± SEM. (D) The donor groups from Figure 1C were analyzed for the frequency of very long HCDR3s (≥28 amino acids in length, *i.e.*, three standard deviations above the mean HCDR3 length). The percentages for each donor are shown, with the mean ± SEM. The p values were determined using a one-way ANOVA. All statistically significant differences are indicated. * = p<0.05, ** = p<0.01, *** = p<0.001.