The CC-chemokine receptor 6 (CCR6) is expressed constitutively at an intermediate level on naïve B cells and is upregulated after activation on pregerminal center (GC) B cells. We hypothesized that it could be involved in the events leading to GC reaction and high-affinity antibody production, and therefore investigated the potential role of CCR6 in B-cell differentiation in vivo. After antigenic challenge of CCR6-/- mice with the T-cell-dependent antigen nitrophenyl-keyhole limpet hemocyanin (NP-KLH), GC B-cell development was found to be accelerated and the number of GC had increased significantly compared with control mice, but the antibodies produced by CCR6-/- B cells were on average of lower affinity. We conclude from these data that the CCR6/CCL20 axis has an important role in regulating the kinetics and efficiency of the GC reaction.