Relative use of individual IGHV genes in HCV⁺and healthy individuals, across the 4 B-cell subsets. Only those IGHV genes that accounted for at least 1% usage in at least 1 B-cell subset are shown. As a numerical measure to quantify the effect of HCV infection on IGHV segment usage, we computed for each IGHV segment the Bhattacharyya coefficient (BC) for posterior distributions of segment usage in HCV⁺ patients vs HD. BC values close to 0 (= 0 overlap between posteriors) indicate that there is a clear difference in the usage of the respective IGHV segment in HCV⁺ patients and HD. BC values close to 1 (= complete overlap of posteriors) mean that the usage of the respective segment is the same in HCV⁺ and healthy individuals. The 30 most significant differences between HCV⁺ patients and HD are annotated with BC. We also performed a further statistical evaluation of the data with the Mann-Whitney U test (supplemental Figure 2; supplemental methods). Whereas some IGHV genes showed a significant differential usage only with 1 or the other test, importantly, the IGHV genes IGHV1-69, IGHV3-30, and IGVH4-59 showed a significantly biased usage by NCSM B cells in HCV patients according to both tests.