Effect of IL-6–signaling inhibitors on TLR7-mediated growth of CLL cells in vivo. (A) Immunodeficient mice were engrafted with 5 × 10⁷ PBMCs, given bi-weekly injections of splenic stromal cell conditioned media (ie, SS) (1 ml) or (B) daily injections of IL-6, treated with resiquimod (100 μg) with or without actemra (100 μg), and euthanized 1 week later. CLL cells in spleens were calculated from total cell counts in a hemocytometer and percentages of human CD5⁺CD19⁺ cells measured by flow cytometry. The results of separate experiments using PBMCs from different patients are shown. (C) Paired differences in splenic CLL cell numbers with and without actemra are shown for all experiments.