Gene expression profiles of naive, memory, B-1 cells, and plasmablasts. The gene expression profile of purified B-cell subsets as defined in Figure 1 was determined and clustering analysis on log2-transformed normalized expression values is shown (red/green scale bar). (A) Dendrogram of hierarchical clustering of different B-cell subpopulations based on the top 100 overexpressed genes discriminating plasmablasts from memory B cells on a red/green map display for over- and underexpressed genes. The scale ranges from 0 (green) to 9.4 (red). (B) Dendrogram of hierarchical clustering of different B-cell subpopulations based on the top 100 overexpressed genes discriminating plasmablasts from the proposed B-1 cells on a red/green map display for over- and underexpressed genes. The scale ranges from 0 (green) to 9.0 (red).