TLR9 and B-cell chronic lymphocytic leukemia: In CLL, the proliferating fraction is in the bone marrow and in the lymph nodes, while the cells in the blood are arrested in G0/G1 phase (34, 41), PB-derived CLL cells do therefore not proliferate in vitro but can be activated by surface Ig-crosslinking or by triggering TLR9 (34).