The Syk inhibitor R406 abrogates induction of CCL3 and CCL4 secretion by CLL cells in cocultures with NLCs. The bars represent the mean (±SEM) CCL3 and CCL4 concentration in CLL cell supernatants from 4 different patients incubated for 24 or 48 hours with NLCs in the presence or absence of the Syk inhibitor R406, as indicated on the horizontal axis. Treatment with R406 significantly inhibited the induction of CCL3 (A) and CCL4 (B) secretion by the CLL cells, as indicated by the asterisks, with P values less than .05 at 24 hours (*) and 48 hours (**). No significant CCL3 or CCL4 concentrations were detected in supernatants of NLCs alone (data not shown).