The CC-chemokine receptor 6 (CCR6) can be detected on naive and activated B cells. Counterintuitively, its absence accelerates the appearance of germinal centres (GCs) and increases the production of low-affinity antibodies. The detailed mechanism of CCR6 function during the humoral response has remained elusive, but previously we identified a distinct CCR6 B-cell population in vivo early after antigenic challenge. In this study, we defined this population specifically as early, activated pre-GC B cells. In accordance, we show that CCR6 is upregulated rapidly within hours on the protein or mRNA level after activation in vitro. In addition, only activated B cells migrated specifically towards CCL20, the specific ligand for CCR6. Lack of CCR6 increased the dark zone/light zone ratio of GC and led to decreased antigen-specific IgG1 and IgG2a antibody generation in a B-cell intrinsic manner in mixed bone marrow chimeras. In contrast, antigen-specific IgM responses were normal. Hence, CCR6 negatively regulates entry of activated, antigen-specific pre-GC B cells into the GC reaction.

The CC-chemokine receptor 6 (CCR6) is expressed constitutively at an intermediate level on naı¨ve 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 À/ À 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 À/ À 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. Navigation of B cells in secondary lymphoid organs is driven by differential expression of the G protein-coupled chemokine receptors and their chemokine ligands. 1-3 After contact with antigen, B cells move to the T-B-cell border directed by the CC-chemokine receptor 7 (CCR7) 4 in order to receive T-cell help. [5][6][7] This cognate interaction between T and B cells results in the formation of T-B conjugates that last for extended periods of time. 5-7 Subsequently, B-cells move to the follicle 4,8 guided by CXCR5, where they undergo a burst of proliferation and form germinal centres (GC) 9-11 that facilitate somatic hypermutation and affinity maturation. CC-chemokine receptor 6 (CCR6) can be detected at a high level on activated B cells that receive T-cell help at the T-B intersection, and subsequently enter the follicle. 7 We addressed the specific role of CCR6 on B cells and found that in its absence, the generation of GC was faster and the number increased. RESULTSTo elucidate the timing of CCR6 upregulation in the context of B-cell activation and T-B cell interaction, we transferred splenocytes, which had been isolated from transgenic mice carrying a nitrophenyl (NP)-specific B-cell receptor (B1-8 low , 3Â 10 7 splenocytes/transfer) into congenic CD45.1 þ recipient mice, and immunized them with NP-keyhole limpet hemocyanin (NP-KLH). After 5 days, using CCR6 and CD45 expression, three populations of donor B cells were distinguishable (Figure 1a). These populations, termed here A, B and C, were analyzed for their expression of GL7 and CD38 (Figure 1b). Population A and C represented naïve and GC B cells, respectively. Population B was CCR6 hi and CD38 þ and was transient between naïve and GC B cells (Figure 1b). The percentage of naïve B cells decreased with time, whereas the percentage of GC B cells increased. The size of the transient population proved to be variable in individual mice, possibly due to small changes in the individual kinetic of the B-cell response (Figure 1c). To determine whether the CCR6 hi B-cell population corresponded to activated blasts or memory B cells, we analyzed their forward scatter/side scatter characteristics, and found that the forwar...

B cells are known to play a dominant pathogenic role in autoimmune conditions such as systemic lupus erythematosus (SLE) and rheumatoid arthritis. In recent times, the chemokine receptor CCR6 and its cognate ligand CCL20 have been shown to play a role in the fundamental kinetics of germinal centres and B cell responses. As CCR6 is found on B cells and is upregulated after activation, we investigated the expression of CCR6 on naive, pre-germinal centre (GC), GC/plasma cell and memory B cells in peripheral B cells of SLE patients and healthy controls using flow cytometry. Pre-germinal centre B cells are found in lower proportions and the expression of CCR6 is increased on B cells of SLE patients, suggesting a role for the chemokine pair in the pathogenesis of the disease. Further studies are needed to explore these preliminary results.

The article was originally published with a missing author. In the recent manuscript, the name of the co-author Murray J. Adams was inadvertently omitted. His name and affiliation have now been added to the author list. The original article was corrected.