Affinity-matured late GC B cells can bind and neutralize heterologous influenza viruses. Related to Fig. 3. (A) Lineage tree with corresponding heavy chain amino acid sequences in clonal family 05.89107.H1N1. Each row corresponds to its aligned node. Each row corresponds to the adjacent tip of the tree. (B) Lineage tree of clonal families 05.111394.H3N2, 05.129238.B/Ph, and 05.173963.H3N2 from participant 05 and 04.113954.B/Ph and 04.46156.B/Ph from participant 04. IGHV and IGHJ gene use is indicated. Cells from which mAbs are derived are labeled with the cell of origin and the week isolated. P values are calculated as described in the methods. (C) Optical density (OD) at 490 nm of A/Singapore/INFIMH-16-0019/2016 H3-binding or B/Phuket/3073/2013 HA-binding mAbs from clonal families in B. (D) Binding of Fabs from clonal family 05.111394.H3N2 to A/Singapore/INFIMH-16-0019/2016 H3 and Fabs from clonal family 04.113954.B to B/Phuket/3073/2013 HA as measured by BLI. (E) Median half-maximal binding concentration of mAbs isolated from GC B cell clonal lineages from participant 04 (purple) and participant 05 (blue) early (week 2/4) or late (week 9/13/17) after vaccination as measured by ELISA to relevant HA proteins. Filled circles indicate the clonal lineage tree is included in the manuscript. Median values are indicated above each column. P value was determined by paired t test. KD, dissociation constant.