Tracking vaccine-specific B cells in persistent GCs. (A and B) Clustering visualized via UMAP of B cells from blood, lymph node (LN), and bone marrow (BM) scRNA-seq samples in participant 05 (A) and participant 04 (B). Each dot represents a cell, colored by phenotype as defined by transcriptomic profiles. Naïve B cells (gold), PBs (red), ABCs (green), GC B cells (blue), LNPCs (red), RMBs (lavender), and plasma cells (PC, red) populations are pooled from all time points (first panel). 2018 QIV–specific cells at each week after vaccination are colored as described. (C) Frequency of 2018 QIV–specific GC B cell clones at the indicated time points in participant 05. Each slice represents one clonal family. The frequency of a clonal family is defined as the percentage of cells in each clonal family among the total GC B cells at each time point (n = 206 at week 2, n = 149 at week 4, n = 293 at week 9, n = 273 at week 13). Colored slices indicate clones identified at multiple time points. N.D., no data. See also Fig. S2; and Tables S3, S4, S5, S6, and S7.