Unsupervised principal component analysis. PCA of the 1174 genes with the highest SD among the 49 samples. The separation of the 5 groups of samples was visualized on a 2-dimensional plot. The coordinates of each sample correspond to its principal component scores. PBB indicates peripheral blood B cells; TBC, tonsil B cells; TPC, tonsil plasma cells; BMPC, bone marrow plasma cells; PPC, polyclonal plasmablastic cells.