In vivo migration of primary leukemic cells obtained from patients with CLL. Rag2^−/−γ_c^−/− mice were injected intravenously with a mixture of CD19⁺ CFSE-high– and CFSE-low–labeled leukemic B cells from the PB of 8 patients with CLL with a different pattern of HS1 phosphorylation (HS1^hyper−p and HS1^p). (A,D) Flow cytometric analysis of preinjection samples: percentages of CFSE-low (peak T) and CFSE-high (peak U) cells are indicated. The plots are gated on 7AAD⁻ CFSE⁺ cells. (B-C) Flow cytometric plots show 7AAD⁻ CFSE-low (peak T, HS1^p; patient no. 6 in Table 2) and CFSE-high (peak U, HS1^hyper-p; patient no. 7 in Table 2) cells obtained from spleen (SP) and BM of a representative Rag2^−/−γ_c^−/− recipient mouse killed 20 hours after cell injection. Percentages of cells falling in fractions T and U are indicated. (E-F) Flow cytometric plots show 7AAD⁻ CFSE-low (peak T, HS1^hyper-p; patient no. 1 in Table 2) and CFSE-high (peak U, HS1^p; patient no. 4 in Table 2) cells obtained from SP and BM of the Rag2^−/−γ_c^−/− recipient mouse killed 20 hours after cell injection. The preferential accumulation of HS1^hyper-p cells versus HS1^p cells in the BM of mice is not affected by CFSE concentration.