Size and composition of the B-cell compartment <i>ex vivo</i> influences B-cell expansion during culture.

<p>Flow cytometry analysis was performed to determine proportions and subsequently calculate absolute numbers of (A) total CD19+ B-cells (blue dots) and (B) IgG+CD19+ B-cells (orange dots) <i>ex vivo</i> and post-culture. <i>Ex vivo</i> proportions of (C) total CD19+ B-cells (blue dots) within viable PBMCs were plotted against the fold change in their absolute numbers, and (D) IgG+ B-cells (orange dots) within total CD19+ B-cells were plotted against the fold change in their proportion within the B-cell compartment. (E) Proportions of IgG+CD19+ B-cells (orange dots) and (F) IgG−CD19+ B-cells (green dots) within viable PBMCs were plotted against the fold increase in their respective absolute numbers post-culture compared to <i>ex vivo</i>. Colored dots show cultures from all 269 stimulated samples (3–7 time points per volunteer), while black dots show the cultures from only the 62 baseline samples (1 for each individual volunteer). The black dashed line indicates the median fold change (with value), grey dotted lines represent the upper and lower limit of the interquartile range. Spearman r and p values are shown for analysis of baseline samples (black dots) from the 62 donors assessed.