Typical organ distribution of human lymphocytes in human/mouse chimera following transplantation of PBMC from a stage 0 BCLL patient. Human/mouse chimera were prepared as described in Fig 2. Two weeks after transplantation of human BCLL cells, mice were killed, and the recovered cells from different organs were isolated on Ficoll and tested by cytofluorometry for triple staining with anti-CD45, anti-CD3, and anti-CD20. Shown are cells recovered from the spleen (A, B, and C), liver (D, E, and F ), and lung (G, H, and I) of a chimera generated from patient no. 2.